REV1 RESUB 1 - ALT2 Pipe Field Perfomance 60-Year Survey2014
DURABILITY OF ALUMINIZED TYPE 2 COATED
CORRUGATED STEEL PIPE EXPOSED
THROUGHOUT THE UNITED STATES
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Prepared for:
NATIONAL CORRUGATED
Elzly STEEL PIPE ASSOCIATION
Technology
August 2014
THIS RESEARCH WAS PERFORMED IN PARTNERSHIP WITH:
Steel Market Development Institute: Construction Market Council
A Business Unit of the American Iron and Steel Institute
25 Massachusetts Ave, NW
Suite 800
Washington, DC 20001
THIS REPORT WAS WRITTEN BY:
J. PETER AULT, P.E
ELZLY TECHNOLOGY CORPORATION
1610 WASHINGTON PLAZA NORTH
RESTON, VA 20190
THIS REPORT WAS PREPARED FOR AND PUBLISHED BY:
NATIONAL CORRUGATED STEEL PIPE ASSOCIATION
14070 Proton Road
Suite 100, LB 9
Dallas, TX 75244
August 2014
DURABILITY OF
ALUMINIZED TYPE 2 COATED
CORRUGATED STEEL PIPE
EXPOSED THROUGHOUT THE UNITED STATES
WRITTEN BY -
J. PETER AULT, P.E. - ELZLY TECHNOLOGY CORPORATION
CO-AUTHOR -
MICHAEL MCGOUGH, P.E. - NATIONAL CORRUGATED STEEL PIPEASSOCIATION
SPECIAL THANKS TO-
JAMES EVANS - AK STEEL CORPORATION
August 2014
Durability of
Aluminized Type 2 Corrugated Steel Pipe
Exposed throughout the United States
Prepared for:
National Corrugated Steel Pipe Association
Prepared by:
Elzly Technology Corporation
August 2014
Executive Summary
The durability of a drainage system is an important consideration for a civil engineer. As a result of
continued interest in improving the durability of corrugated steel pipe (CSP) products, the CSP industry
has sponsored extensive research over the past several decades on improved coating materials.
Aluminized Type 2 CSP was developed in 1952 to be a more durable coating than zinc in many of the
common installation environments. In the early 1950's, over 125 Aluminized Type 2 corrugated steel
pipes were installed through a collaborative effort of Armco, now AK, Steel and over 20 county and
state highway departments. Starting at the anniversary of 30 years of service, an inspection was
conducted approximately every 10 years thereafter to track the performance of specific installations.
Since that time, the material performance of sites in Maine, Maryland, Michigan, Ohio, Iowa, Illinois,
Missouri, Mississippi, Alabama, Georgia, South Carolina, Louisiana, Texas, Kansas, Oklahoma, Colorado,
Oregon, Utah, New Mexico, California and Washington have been documented. These studies, in
addition to the work conducted by the Federal Highway Administration (FHWA) and multiple state DOT's
have continued to demonstrate the durability of Aluminized Type 2 CSP .
The present study was focused on documenting performance of Aluminized Type 2 CSP in long term
installations as well as determining the viability of current technologies for measuring steel and coating
thicknesses. Sites in this study were selected from AK Steel's 50-year report, FHWA's report titled
"Durability Analysis of Aluminized Type 2 Corrugated Metal Pipe.", and manufacturer records. In total,
26 core samples were removed and analyzed for coating thickness, pit depth, and alloy layer. These
samples of both helical and riveted pipe ranged between 30 and 60 years in service. Soil and water
samples were gathered from the site and analyzed for resistivity, pH and chlorides when available.
The data confirms current service life guidance for Aluminized Type 2 CSP, where 16 gage steel provides
a minimum of 75 years of service life when the FHWA abrasion level is 2 or less, the pH range is from 5
to 9 and the resistivity is greater than 1500 ohm -cm or greater than 5000 ohm -cm with a pH of 4.5 to 5.
The soil side of all but six of the samples has 100 percent coating remaining with only one of the six
having been exposed for less than 60 years. The water side of the samples exhibit varying degrees of
degradation due to water corrosivity, wet and dry cycling, bedload and water flow. Of the few sites with
pitting, it was found mainly on the upstream side of the corrugation in the invert. All pipes are currently
functioning as intended at this point in their life and would be expected to meet the design service life
of 75 or 100 years.
For future inspections, it is recommended that advantage be taken of newer technologies for
measurement of both coating thickness and overall pipe thickness. The use of Dry Film Thickness (DFT)
gages and Ultrasonic Thickness (UT) gages allow for a larger sampling size for each pipe. The larger
sample size can be produced in less time than it normally takes to drill out a core and analyze a single
sample. A larger performance database will continue to increase the level of confidence in the durability
of Aluminized Type 2 CSP.
1
Table of Contents
ExecutiveSummary.......................................................................................................................................1
Background................................................................................................................................................... 3
Armco / AK Steel Corporation Studies...................................................................................................... 3
FH W A-F LP-91-006..................................................................................................................................... 4
FHWA-RD-97-140......................................................................................................................................4
FieldStudies..................................................................................................................................................5
InspectionProcedure................................................................................................................................5
DataCollection..........................................................................................................................................7
Discussionand Analysis.................................................................................................................................9
Durabilityand Service Life........................................................................................................................ 9
EnvironmentalInfluences.......................................................................................................................
11
Inspection Procedure Enhancements.....................................................................................................14
Appendix A — Detailed Data from Each Site................................................................................................17
Appendix B — Recommended Inspection Procedure..................................................................................18
2
Background
The durability of a drainage system is an important consideration for a civil engineer. As a result of
continued interest in improving the durability of corrugated steel pipe (CSP) products, the CSP industry
has sponsored extensive research over the past several decades on improved coating materials. A
synthesis study funded through the Transportation Research Board (TRB) discusses drainage pipe
durability at length.'
Aluminized Type 2 (Aluminized) steel was first introduced as a corrugated steel pipe material in 1952-53.
This type of corrugated steel pipe is fabricated from high strength steel coils that have been hot dip
coated in a bath of commercially pure aluminum, creating a metallurgical bond to the base metal. The
aluminum material protects the steel by first forming a passive aluminum oxide layer, which provides
longer protection over a broader range of environments than comparable zinc coatings. The second
layer of defense is the hard aluminum -iron alloy layer itself. Several independent studies have
demonstrated excellent performance of aluminized steel in the most common types of culvert
installations. The material manufacturer has also conducted long-term studies of Aluminized culvert
performance for over half a century. Following is a brief discussion of studies conducted by the
manufacturer and the Federal Highway Administration (FHWA) which include the pipes that make up
the majority of this study.
The sites that were selected for this study are taken from previous manufacturer reports, the FHWA
study referenced and the addition of several new sites identified through industry. The reduction in the
numbers of sites inspected over the course of these studies has been attributable to many factors
including: urbanization or other changes in land use, abandonment, submergence or the inability to
locate. Several sites were either removed from service or not included due to exposure to severe
abrasion conditions, while other sites were removed or rehabilitated due to deterioration in the
adjacent galvanized sections.
Armco / AK Steel Corporation Studies
In 1952-53, 137 Aluminized Type 2 corrugated steel pipes were installed through a collaborative effort
of the manufacturer and several state departments of transportation. Since that time, performance at
sites in Iowa, Illinois, Missouri, Mississippi, Texas, Kansas, Oklahoma, Colorado, New Mexico, California
and Washington have been documented. The reports for these locations document the backfill
material, water quality and the soil side and water side corrosion.
Three primary published reports resulted from the 1952-53 study of Aluminized Steel Type 2 corrugated
steel pipes. These reports included a 30-year, 42-43-year and 50-year evaluation. The 30-year report
investigated 58 sites in 14 states. The report focuses on water side corrosion, noting that "no sites had
1 Gabriel, Lester H., Service Life of Drainage Pipe, NCHRP Synthesis 254, Transportation Research Board
Washington, DC, 1998.
3
severe soil side influences." Based on the data in this report, usage guidelines were developed which
reflected the ability of Aluminized Type 2 to tolerate more severe environmental conditions than
traditional CSP materials.
The report titled Aluminized Steel Type 2 Corrugated Steel Pipe Durability Update: 1995; Field
Performance of Pipes in Service for 42-43 Years documents the performance of 34 of the original sites in
11 states as well as an additional 24 younger sites in 7 states. The study concluded that the data was
"indicative of projected service life of 75 years minimum at 16 gage in normal environments." The 50-
year evaluation included 22 of the original sites in 9 states. The data in this report was consistent with
the present design guidance for 75 and 100-year service life.
FHWA-FLP-91-006
An FHWA sponsored study, Durability of Special Coatings for Corrugated Steel Pipe was conducted in
1991. This study included a comprehensive literature review and field study of the service life of
different CSP coating systems, using galvanized as a performance baseline. The study reviewed both
metallic (galvalume and Aluminized Type 2) and non-metallic (bituminous, polymer, concrete etc.)
coatings that could potentially produce a service a life in excess of 50 years. The study concluded that
CSP life cycle can be extended past 50 years if the proper coating was used under proper environmental
conditions. The study was favorable to the Aluminized coating.
FHWA-RD-97-140
Another FHWA sponsored study, Durability Analysis of Aluminized Type 2 Corrugated Metal Pipe was
conducted as a follow up to FHWA-FLP-91-006. In this study, a focus was made on Aluminized Type 2
pipes, including those inspected in the 1991 FHWA study. At the time of inspection most of these
sections of pipe had 14-16 years of service.
This study attempted to incorporate the effects of bed load abrasion into service life potential. Previous
studies neglected this factor, which contributes to variability in the observed durability. This study
concluded that Aluminized CSP has the potential to last up to eight times longer than galvanized CSP on
the soil side and 3.5 times longer on water side, depending on the exact environment. It also concluded
that two pitting tendencies were observed. The higher pitting tendency was influenced by abrasion
from the bed load and the lower pitting tendencies appeared to be linear in time.
4
Field Studies
Inspection Procedure
Most of the present field inspections were performed by the Chief Engineer of the National Corrugated
Steel Pipe Association with assistance from local Department of Transportation and manufacturer
representatives. Elzly participated in the inspection of Santiam Highway, Oregon locations. The
equipment used during each inspection included:
• Digital Camera
• Dry Film Thickness gage (DFT)
• Ultrasonic Thickness gage
• Cordless drill with 1.5" hole saw bit
• pH paper
• Sample containers
• Assorted tools (shovel, machete, scrub brushes, hand tools)
At each site the following tasks were completed:
1. Photograph the specific pipe being evaluated
2. Use pH paper to evaluate water, if present, and evaluate bedload
3. Collect soil and water samples for evaluation
4. When possible, collect core sample from pipe, to be micro- and macroscopically evaluated
5. Use DFT gage to measure remaining Aluminum coating
6. Use Ultrasonic thickness gage to measure total thickness of corrugated steel pipe
In most cases duplicate core samples were removed from each pipe. One sample was returned to AK
Steel while the other sample was returned to Elzly Technology for analysis. Analysis was completed in
effort to determine the extent of coating degradation, if any, and to determine the extent of any pitting.
The samples were prepared using standard metallographic techniques. All samples were photographed
(on both water and soil side) in their "as -is" state, after cleaning with brush and water and after glass
bead blasting to remove all corrosion product. The light glass bead process does not remove significant
amounts of the Aluminized coating. Figure 1 shows a representative sample as received and after
abrasive blasting. Once the samples are cleaned, the extent of remaining coated surface is estimated
and the deepest pits are measured using a mechanical pit gage.
5
Fairplay, CO "as -received" Fairplay, CO "post -blasting"
Figure 1. Representative Sample Cleaning
Precision cuts were made through an area of interest on each sample. This was often through the most
severe pitting found on the sample, but this single pit may not be representative of the pitting severity
along the whole sample or the whole pipe. These pieces were mounted in epoxy and finished with a
progressively finer abrasive. Finally, a Nital etchant was used to expose the aluminum -iron alloy formed
during the pipe sheet production process. Once sample preparation was complete the samples were
able to be observed under a microscope. Digital images were analyzed to determine the thickness of
the Aluminized coating, alloy layer (when aluminum was removed) and depth of any pits observable
within the sample. Figure 2 shows representative measurements.
16
Figure 2. Representative Micrograph
0
Data Collection
Table 1 shows an inventory of the pipes evaluated grouped by the study with which they were originally
associated.
Table 1. Inventory of Pipes Evaluated
Original Armco/AK Steel Sites
Approximately 60 ears old
Sites From FHWA-RD-97-140
Test Sites
not in previous studies
• Morgan Co., IL
• Santiam Highway, OR
• Anlauf, OR
• Marshall Co., IA (2 pipes)
(9 sites) — 28 yrs old
• Jefferson, OR
• Carter Co., MO
0 Ripley, ME — 30 yrs old
• Snellville, GA
• Dickinson Co., KS
0 Natchez Trace Parkway, AL
• Memrancook, NB, Canada
• Pratt Co., KS
(3 pipes) 28 yrs old
• Fairplay, CO
• Bernalillo, NM
• El Dorado, CA
• San Benito, CA
A core sample was removed from the invert of each pipe in the study whenever possible. Some pipes
were obstructed by high water or soil, making it impossible to remove a sample from the invert for
testing. In total 26 samples were evaluated. Soil and water samples were collected, when possible, and
evaluated for resistivity, pH and chlorides.
Table 2 shows a summary of the data for each pipe. In this table we show the type of pipe and
approximate age, for those that are known, and water and soil side data. For both sides a visual
estimate was made of the total percentage of the coupon surface area which has in -tact aluminum
coating. Measurements of the maximum thickness of coating remaining, the minimum thickness of
coating, maximum pit depth and thickness of alloy layer were made along the cross-section observed
under the microscope. This section was selected in an attempt to be able to view the most significant
pitting and coating loss on the coupon. An important consideration when reviewing the data, is that
this is not necessarily representative of the entire pipe surface. In most cases the pipe invert
experiences the most significant coating loss and pitting. Appendix A contains data and photographs
for each core sample.
7
Table 2.Data from Removed Samples
Location
State
Age
Water Side
Soil Side
FHWA
Abrasion
Level
% Coating
Remaining
Max AL
(mils)
Min AL
(mils)
Max Pit
(mils)
Resistivity
pH
% Coating
Remaining
Max AL
(mils)
Min AL
(mils)
Max Pit
(mils)
Resistivity
pH
Natchez Trace
310.2
AL
31
3
80
1.25
0.00
2.50
NV
NV
100
1.63
0.73
0.87
NV
NV
Natchez Trace
311.9
JAL
31
1 1
5
0.00
0.00
23.00
NV
NV
100
1.61
0.72
1.31
NV
NV
Natchez Trace
312.4
AL
31
1
100
2.03
0.00
1.38
NV
NV
100
2.55
0.84
16.00
NV
NV
Fairplay County
CO
60
3
0
0.00
0.00
8.50
NV
NV
0
0.00
0.00
5.21
3218
6.4
Snellville
GA
30
2
100
3.68
0.00
4.31
NV
6
100
2.32
1.24
1.21
NV
NV
Marshall County
#5
IA
60
2
40
0.89
0.00
2.57
NV
NV
20
1.40
0.00
1.31
1570
7.6
Marshall County
#7
IA
60
2
1 90
1.78
0.00
1.23
710
6.7
95
1.38
0.58
0.84
1330
7
Morgan County
IL
60
2
85
1.71
0.00
8.00
2174
6
100
2.53
0.00
1.97
2860
7
Dickinson County
KS
60
2
0
0.00
0.00
37.00
NV
NV
5
0.00
0.00
0.73
NV
NV
Pratt County
KS
60
2
5
0.00
1 0.00
12.00
1 NV
NV
5
0.00
0.00
1 14.00
NV
NV
Ripley
ME
30
2
0
0.00
0.00
41.00
NV
6
100
1.13
0.00
2.32
NV
NV
Carter County
MO
60
1
10
0.00
0.00
10.50
NV
NV
100
1.65
0.00
0.00
1420
6.7
Bernalillo
NM
60
2
0
0.00
0.00
26.00
NV
NV
0
0.00
0.00
57.00
NV
NV
Anlauf
Oregon
NA
2
90
2.69
0.77
4.97
10870
5
100
1.87
0.55
1.35
2860
NV
Jefferson
Oregon
NA
3
1 60
2.78
0.00
81.00
10010
100
2.361
1.63
0.00
81.00
NV
NV
Santiam Highway
18+20
Oregon
28
2
80
2.31
0.00
1.54
55500
4.5
100
1.45
0.00
0.94
14300
NV
Santiam Highway
38+12
loregon
28
2
65
1.72
0.00
11.00
23810
5
100
2.54
0.00
1.60
9440
NV
Santiam Highway
44+50
Oregon
28
2
55
1.05
0.00
2.28
29410
5.5
100
3.01
1.00
0.87
29030
NV
Santiam Highway
90+38
10regon
28
3
5
0.00
0.00
51.50
18520
5.5
30
0.88
0.00
35.50
14410
NV
Santiam Highway
100+15
loregon
28
1
95
1.66
0.00
5.00
28570
5
100
1.42
0.87
3.38
14350
NV
Santiam Highway
104+45
Oregon
28
3
10
0.00
0.00
20.00
29410
4.5
100
2.09
0.93
1.16
14700
NV
Santiam Highway
123+76
Oregon
28
2
100
1.07
0.00
1.20
27780
5
100
1.46
0.00
1.13
31460
NV
Santiam Highway
New Site 1
Oregon
28
1
95
1.58
0.37
0.67
NV
NV
100
3.04
0.55
0.00
14470
NV
Santiam Highway
New Site 2
Oregon
28
1
95
2.02
0.00
9.00
NV
NV
100
2.18
0.94
1.02
NV
NV
Memrancook
Canada
New Brunswick
15
2
100
2.54
0.08
0.78
NV
6
100
3.02
0.00
1.55
NV
NV
Note: The Albuquerque, NM sample had such significant general corrosion that no original surface was available to make a measurement under the
microscope. The reported maximum pit at this site is based on a needle micrometer measurement.
................................... ............................
8
Discussion and Analysis
Durability and Service Life
All of the pipes inspected in this study were still performing their intended function. Two pipes were
observed along the Natchez Trace in Alabama which had invert perforation. These locations were
documented in previous FHWA studies. It is believed that these pipes were subject to abrasion beyond
that which is recommended for Aluminized Type 2 service. Coupons were not removed from these
inverts. Of the remaining locations, only six pipes had pitting in excess of 20% of the overall pipe
thickness. Two of those samples had pitting from both soil and water side while the remaining four only
had pitting from the water side.
The soil side of all but six of the samples has coating remaining on 100 percent of the surface. Of those
six samples only one has been exposed for less than 60 years. The water side of the samples
experiences varying degrees of degradation due to water corrosivity, wet and dry cycling and bed load
and flow. All but nine of the samples had at least 40% of the surface coated. Based on the observations,
all of the pipes are currently functioning as intended at this point in their life (30-60 years of service).
The observed pipe conditions are consistent with the design guidance provided for Aluminized Type 2
CSP.
In an attempt to get a broader perspective of the performance of Aluminized coated CSP over time, all
available data from AK Steel's reports (30, 43 and 50 year), FHWA-FLP-91-006 and FHWA-RD-97-140 and
the current inspections was compiled. Each pipe was categorized into one of four categories based on
the depth of pitting and extent of coating loss. Table 3 shows the rating scheme. In all, over 170
individual inspections were recorded and categorized. Figure 3 presents the total number of
observations in each category. Note that the perforated pipes are those which have previously been
identified as experiencing abrasion beyond the recommended level.
Table 3. Ratine Criteria
Aluminized Coating Attack
100% covered 100% Exposed
Less than 2 mils
.Y
2-6 mils
a
Greater than 6 mils
Perforation
0
24.0%
22.0%
2.0%
Figure 3. Distribution of Conditions
Figure 4 shows the same data as Figure 3 except it is separated by pipe age at the time of the
inspections. The most data was collected when the pipes had between 21 and 30 years of service. At
that period the number of pipes in the green category is very high. This shows that through 30 year of
service almost no pitting is present (38 pipes). There are ten samples in each of the yellow and orange
categories. Although these pipes are beginning to show signs of wear they still hold most of their steel
substrate and, for those in yellow, often some of the Aluminized coating. As the pipes age a shift in the
data can be seen. Note that no inspections were conducted of pipe with 31 to 40 years of service. At
the 41 to 50 years of service sample categories begin to shift toward the yellow and orange. This means
that around 50 years of service the Aluminized coating becomes penetrated at a higher rate. Following
this phase of the coating breakdown the base metal steel will then begin to corrode. A limited number
of sites were inspected at 60 years of service. Of the sites inspected, all remained in the same
categories from their 50 year inspection.
10
Figure 4. Samples Categorized by Grade and Age
Once the aluminum oxide and alloy layers are consumed the corrosion of the base steel will begin. The
corrosion of steel in soil has been extensively studied. In the situation of CSP the soil side can be
estimated using many of these models depending on soil characteristics. Water side estimates will vary
in time with water characteristics. Using a typical model we could expect base metal steel corrosion
rates of roughly 0.5 mils per year from the soil side and 2 mils per year at the invert under the waterline
in an aggressive water -side environment. Considering this scenario of corrosion rates, a 16-gage (0.064
in) CSP will last more than 25 years beyond the coating life before perforation occurs.
Environmental Influences
CSP durability guidance is predominantly based on soil and water chemistry (typically resistivity and pH,
although water hardness, chloride and sulfate content is sometimes also used). Obviously, soil and
water conditions can change over the service life of the pipe. For example, changes in land use may
cause the water run-off to become acidic or highly saline, both of which will increase corrosion rate.
The issue of variability in water characteristics was briefly investigated in the previously referenced
FHWA Study. Including the present study, there are three sets of soil and water data from the inspected
sites at Natchez Trace Parkway, Alabama (NT) and Santiam Highway, Oregon (SH). The three sets of
data were compiled for analysis. Figures 5 through 8 present how water and soil conditions can change
over the service life of these pipes. The differences among the data sets are not terribly significant
relative to the CSP service life selection criteria. However, the 1991 and 2000 data appear more
consistent than the 2013 data. The 2013 data seems to suggest that the Oregon water and soil are
higher resistivity, though it is difficult to tell if this is a seasonal effect, random observation, or a long-
term trend.
11
F,
N
Resistivity (ohm cm)
I- N W A Lrl Dl
O O O O O O
O O O O O O O
NT 310.6 IN
NT 311.9 ■
NT312.4 ■
NT 312.4
SH 13+00
SH 18+20
SH 38+12
SH 38+12
SH 44+50
SH 90+38
SH 100+15
SH 104+45
SH 104+45
SH 123+76
NT 310.0
NT 310.1
♦
■ �J c
♦ R m
■
�
■
S
� v
3
00
M
Vf
3
f"h
rt
rF =
■
N N F-
O O lD
1 O lD
W 0 h-
O N 4�-
NT 310.6
pH
M
W
O N �
■
NT 311.9
NT312.4
NT 312.4
SH 13+00
■
SH 18+20
SH 38+12 ►
SH 38+12
e-F
SH 44+50
SH 90+38
_
SH 100+15 ►
SH 104+45
SH 104+45 ►
■
SH 123+76 ►
NT 310.0
NT 310.1
■
■
O O
LD
N O
W 0
lD
N
14
12
10
8
x
a 6
4
2
J
Soil pH
■
i
i
■
■
1,q 0i -;Zl: -z� oo�oW rMM O ri
o� N � 0 -tT �o 0��m..+v.
M M M M oooo o o
r-1 ri M M � 0) O O O N M M
Z Z Z to LnLnN V)N M _ _ M Z Z
Ln V) to
35000
E 30000
'j 25000
o 20000
15000
N 10000
a
°C 5000
0
Figure 7. Change in Soil pH
Soil Resitivity
l0 01 ':j: -;t O
O�
O
N
N
O
W
M
M
M
to O ri
+ O O
rr-1 rN-1 rN-1 +
M M M M rro
1
0+0
-1
0+0
M
W
M't
O
Ol
O
O
O
O
N M M
Z Z Z
Z Z Z Z (n
Ln
Ln
N
N
N
'
M
'
_
I
_
I
M Z Z
"I
to
Ln
to
Figure 8. Change
in Soil Resistivity
♦ 1991
■ 2000
♦ 1991
■ 2000
2013
One additional important parameter in the study of CSP is the bedload experienced. The effect of
bedload on Aluminized pipe is obvious from the wear patterns in the aluminum oxide layer. As would
be expected, bedload only wears the Aluminized coating from the upstream side of the corrugation.
Figure 9 and Figure 10 show examples with wear on one side of the corrugation. The lower portion of
the sample is a darker color, because bare steel is exposed due to abrasion. Analysis of the pits on each
sample reveals two unique characteristics of pitting. In samples where abrasion is a clear concern we
see a large density of pits on the upstream half of the sample (see Figure 9). These pits typically have a
wide mouth in comparison to their depth, and are also deeper than most general corrosion pits. Pitting
13
which is associated with general corrosion typically has a low pit density, is scattered throughout the
entire surface area of the sample and has shallower depth than pits in areas subject to abrasion.
Typically, these pits are also much narrower than those found in abrasion areas. If abrasion levels
beyond those recommended are present, a decrease in service life is to be expected.
Water flow
. __
fmwm
e^va
Figure 9. Coating removed due to bed load Figure 10. Coating removed due to bed load
Inspection Procedure Enhancements
As part of this inspection an investigation was conducted to determine if enhancements could be made
to the inspection techniques. With current techniques, a core sample (often multiple) is taken from
each pipe. This core sample is physically evaluated using pit gages, microscopic and visual techniques.
The process is somewhat tedious and leaves a hole in the pipe (though observation of sample locations
twenty years after they were taken shows no adverse effect on the pipe).
During this project, we evaluated the use of electronic Dry Film Thickness (DFT) gages to measure
coating thickness and Ultrasonic Thickness gages to measure remaining pipe wall thickness. These tools
eliminate the need to remove a core sample to determine the degradation rate of the pipe. DFT gages
use electronic circuitry to convert a reference signal into coating thickness when a non-magnetic coating
is applied over a ferrous or non-ferrous substrate. When measuring on Aluminized Type 2 CSP it is
important to verify the gage reading on an aluminized sample of known thickness. Electronic gages
require a field adjustment to a standard coating of known thickness. The gages will also provide more
accurate readings on flat surfaces versus the crest of the corrugation.
Table 4 compares coating thickness measured using an electronic DFT gage and that determined from
microscopic evaluation of core samples. The differences are easily explained by sample size.
Microscopic measurements can only be made along a relatively short cross section (nominally one inch
long) and reflect an observation of a very small cross section at nominally 10OX magnification.
14
Electronic DFT measurements are made throughout the pipe and reflect an average thickness
measurement over the probe diameter.
Table 4. Microscopic vs. Electronic Coating Thickness
Location
Median Microscopic
Thickness Measurement (mils)
Coating Thickness Gage Reading
Average mils
Range mils
100+15
1.66
1.56
1.18-2.08
38+12
1.72
1.93
1.33-3.38
44+50
1.05
1.77
1.54-2.15
Anlauf
3.19
2.12
1.54-3.09
Exit 244
2.79
2.70
1.81-3.88
New Site 1
1.58
1.32
0.99-1.65
New Site 2
2.02
1.28
0.87-1.51
Figure 11 illustrates how coating thickness can vary across a sample even with small cross sections. In
this image a coating thickness of over 5 mils is measured in one location with only 2 mils of coating
thickness a short distance from that.
Figure 11. Potential Variation in Coating Thickness
Ultrasonic Thickness gages are used to measure overall thickness of a material. With the assistance of a
conductive gel, the gage emits an ultrasonic wave into the material. By measuring the time and
amplitude of the reflective wave off the material boundary it can accurately measure the material
thickness to within .001". The measurement is not sensitive to small, isolated pits, therefore the
measurement is more indicative of general thinning versus narrow mouthed pits. If the depth of narrow
mouth pits are significant, a needle pit depth gage could potentially be used to measure them in the
15
field if they can be accessed. Because of variability in sheet thickness, it is recommended that reference
thickness measurements be made at the top of the pipe where coating loss is unlikely and compared to
the invert where thickness loss is typically the worst. Figure 12 presents UT measurements made in
Oregon during this study.
0.160
y 0.140
c 0.120
5
= 0.100
IE
0.080
0.060
_Q 0.040
a 0.020
0.000
pt'
Pipe Location (Oregon Sites)
Figure 12. Comparison of Pipe wall thickness measurements.
■ Invert
■ Reference
The addition of these tools to the standard testing procedure will prevent unneeded removal of core
samples. Additionally, less total time will be required for inspection. The extra time spent taking
measurements in the field is significantly less than that required to microscopically analyze each sample.
Another benefit of using digital gauges is a larger sample size, when using core samples the coating
thickness and pit depth can only be measured over a small cross section. The removed section may not
be representative of the whole pipe's condition, a situation that will create problems. Using the gages
many measurement can be made over the entire pipe. Doing it this way will provide a clearer picture of
the condition of the pipe. Unfortunately, no coating measurement can be made underwater, even in
just an inch or two of water which normally a core sample can still be removed from.
Appendix B contains a recommended standard inspection procedure for use with future inspections.
16
Appendix A - Detailed Data from Each Sample
17
Natchez Trace 310.2, Alabama
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
54"
16 (0.064 IN)
ESTIMATED 1984
AUGUST, 2012
PROFILE
COATING
SOIL DATA
WATER DATA
3 X 1
ALUMINIZED TYPE 2
PH: N/A
PH: 5
RESISTIVITY: 2,860 Q-CM
RESISTIVITY: 10,870 O-CM
FHWA ABRASION LEVEL: 3
CHLORIDES: DRY
CaCO3: DRY
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
WATER SIDE ALUMINUM COATING DATA:
Surface area coated
Minimum thickness:
Maximum thickness
Maximum pit depth
100%
0.73 mils
1.63 mils (41.5 µm)
1.31 mils
Surface area coated
Minimum thickness:
Maximum thickness
Maximum pit depth
80%
0.00 mils
1.25 mils (32 µm)
2.73 mils
Natchez Trace 310.2, Alabama
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP AVG = 0.057
• INVERT AVG = 0.062
* Avg of a minimum of 4 readings after cleaning using TI-25M Ultrasonic Wall Thickness Gauge
COMMENTS:
• Pipe is in good condition
• Installed in an abrasive environment
Natchez Trace 311.9, Alabama
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
72"
16 (0.064 IN)
ESTIMATED 1984
AUGUST, 2012
PROFILE
COATING
SOIL DATA
WATER DATA
3 X 1
ALUMINIZED TYPE 2
PH: N/A
PH: N/A
RESISTIVITY: N/A
RESISTIVITY: N/A
FHWA ABRASION LEVEL: 1
CHLORIDES: DRY
CaCO3: DRY
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated
• Minimum thickness:
• Maximum thickness
• Maximum pit depth
100%
0.72
1.61 (41 µm)
0.87 mils
• Surface area coated
• Minimum thickness:
• Maximum thickness
• Maximum pit depth
5%
0.00
0.00
23.00 mils
Natchez Trace 311.9, Alabama
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP AVG = 0.060
• INVERT AVG = 0.052
* Avg of a minimum of 4 readings after cleaning using TI-25M Ultrasonic Wall Thickness Gauge
COMMENTS:
• Pipe is in good condition
• No pavement distress
Natchez Trace 312.4, Alabama
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
18"
16 (0.064 IN)
ESTIMATED 1984
AUGUST, 2012
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: N/A
RESISTIVITY: N/A
RESISTIVITY: N/A
FHWA ABRASION LEVEL: 1
CHLORIDES: DRY
CaCO3: 100 PPM
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
WATER SIDE ALUMINUM COATING DATA:
Surface area coated
Minimum thickness:
Maximum thickness
Maximum pit depth
100
0.84 mils
2.55 mils (65 µm)
16.00 mils
• Surface area coated
• Minimum thickness;
• Maximum thickness
• Maximum pit depth
100%
0.00 mils
2.03 mils (51 µm)
1.38 mils
Natchez Trace 312.4, Alabama
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP AVG = 0.060
• INVERT AVG = 0.060
* Avg of a minimum of 4 readings after cleaning using TI-25M Ultrasonic Wall Thickness Gauge
COMMENTS:
• Pipe and coating are in good condition
• No pavement distress
El Dorado/Georgetown, California
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
18"
16 (0.064 IN)
ESTIMATED 1952
NOVEMBER, 2012
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: 6.6
PH: DRY
RESISTIVITY: 6,430 Q-CM
RESISTIVITY: DRY
FHWA ABRASION LEVEL: 1
CHLORIDES: DRY
CaCO3:DRY
IMAGES:
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.059 (0.059, 0.059, 0.058, 0.058, 0.059)
• INVERT: AVG = 0.058 (0.059, 0.058, 0.057, 0.059, 0.059)
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns):
• TOP: 37
• INVERT: 31
*Avg of a minimum of 4 readings after cleaning using DCF3000FX
COMMENTS:
• Aluminized Type 2 coating in good condition
• No pavement distress
• Previous trepan holes were not corroded further
San Benito, California
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
30" - RIVETED
14 (0.079 IN)
ESTIMATED 1952
NOVEMBER, 2012
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: 5.1
PH: DRY
RESISTIVITY: 630 Q-CM
RESISTIVITY: DRY
FHWA ABRASION LEVEL: 1
CHLORIDES: DRY
CaCO3: DRY
IMAGES:
ULTRA -SONIC PIPE THICKNESS (IN):
• INVERT: AVG = 0.070 (0.070, 0.071, 0.068, 0.072)
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
COMMENTS:
• Did not appear to be any coating remaining at the invert
• No pavement distress
• Local property owner says they work well
Fairplay, Colorado
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
24"
14 (0.079 IN)
ESTIMATED AT 1952
JUNE, 2012
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: 6.4
PH: DRY
RESISTIVITY: 3,218 Q-CM
RESISTIVITY: DRY
FHWA ABRASION LEVEL: 3
CHLORIDES: DRY
CaCO3: DRY
IMAGES:
.y.
SOIL SIDE ALUMINUM COATING DATA:
WATER SIDE ALUMINUM COATING DATA:
E--- - I F - MZ-- I I: -
• Surface area coated:
0%
• Minimum thickness:
0.00
• Maximum thickness:
0.00
• Maximum pit depth:
8.50 mils
• Surface area coated:
0%
• Minimum thickness:
0.00
• Maximum thickness:
0.00
• Maximum pit depth:
5.21 mils
Fairplay, Colorado
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.078
• INVERT AVG = 0.078
* Avg of a minimum of 4 readings after cleaning using TI-25M Ultrasonic Wall Thickness Gauge
COMMENTS:
• There was no pavement distress
• No further corrosion of trepan holes
• Pipe is in good condition
Snellville, Georgia
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
48"
16 (0.064 IN)
ESTIMATED 1993
JULY, 2012
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: 6
RESISTIVITY: N/A
RESISTIVITY: N/A
FHWA ABRASION LEVEL: 2
CHLORIDES: N/A
CaCO3: 100 PPM
IMArFC-
SOIL SIDE ALUMINUM COATING DATA:
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated:
• Minimum thickness:
• Maximum thickness:
• Maximum pit depth:
100%
1.24 mils
2.32 mils (60 µm)
1.21 mils
• Surface area coated
• Minimum thickness;
• Maximum thickness
• Maximum pit depth
100%
0.00 mils
3.68 mils (93 µm)
4.31 mils
Marshall County #5, Iowa
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
36" - RIVETED
12 (0.109 IN)
ESTIMATED AT 1953
MAY, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: 7.6
PH: N/A
RESISTIVITY: 1,570 Q-CM
RESISTIVITY: N/A
FHWA ABRASION LEVEL: 2
CHLORIDES: DRY
CaCO3: DRY
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
• Surface area coated: 20%
• Minimum thickness: 0.00 mils
• Maximum thickness: 1.40 mils (35.5 µm)
• Maximum pit depth: 1.31 mils
Marshall County #5, Iowa
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated:
40%
• Minimum thickness:
0.00 mils
• Maximum thickness:
0.89 mils (22.5 µm)
• Maximum pit depth:
2.57 mils
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.109
• INVERT: AVG = 0.111
* Avg of a minimum of 4 readings after cleaning measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns):
• TOP: 41
• INVERT: 24
*Avg of a minimum of 4 readings after cleaning
COMMENTS:
• Pipe in good condition
• No pavement distress
• No further corrosion of previous trepan holes
Marshall County #7, Iowa
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
36" - RIVETED
12 (0.109 IN)
ESTIMATED AT 1953
JUNE, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: 7
PH: 6.7
RESISTIVITY: 1,330 Q-CM
RESISTIVITY: 710 Q-CM
FHWA ABRASION LEVEL:2
CHLORIDES: DRY
CaCO3: DRY
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
WATER SIDE ALUMINUM COATING DATA:
Surface area coated
Minimum thickness
Maximum thickness
Maximum pit depth
Surface area coated:
Minimum thickness:
Maximum thickness:
Maximum pit depth:
95%
0.58 mils
1.38 mils (35 µm)
0.84 mils
90%
0.00 mils
1.78 mils (45 µm)
1.23 mils
Marshall County #7, Iowa
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.114
• INVERT: AVG = 0.110
* Avg of a minimum of 4 readings after cleaning measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns):
• TOP: 44
• INVERT: 17
*Avg of a minimum of 4 readings after cleaning
P'AAAI�ALI�ITC.
• Pipe in good condition
• No pavement distress
• No further corrosion of previous trepan holes
Morgan, Illinois
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
36" - RIVETED
12 (0.109 IN)
ESTIMATED AT 1953
MAY, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: 7
PH: 6.0
RESISTIVITY: 2,860 Q-CM
RESISTIVITY: 2,175 Q-CM
FHWA ABRASION LEVEL: 2
CHLORIDES: N/A
CaCO3: 200 PPM
IMAGES:
r�
v,.
SOIL SIDE ALUMINUM COATING DATA:
k
F�
F -ALL. �lN��plrtt
Lv
• Surface area coated: 100%
• Minimum thickness: 0.00 mils
• Maximum thickness: 2.53 mils (64 µm)
• Maximum pit depth: 1.97 mils
Morgan, Illinois
WATER SIDE ALUMINUM COATING DATA:
F
-c
• Surface area coated:
85%
• Minimum thickness:
0.00 mils
• Maximum thickness:
1.71 mils (43 µm)
• Maximum pit depth:
8.00 mils
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.110
• INVERT: AVG = 0.111
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns):
• TOP: 51
• INVERT: 31
*Avg of a minimum of 4 readings after cleaning
COMMENTS:
• Pipe in good condition
• No pavement distress
• No further corrosion of previous trepan holes
Dickinson County, KS
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
36" - RIVETED
12 (0.109 IN)
ESTIMATED AT 1953
MAY, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: 7.1
PH: N/A
RESISTIVITY: 1,640 Q-CM
RESISTIVITY: N/A
FHWA ABRASION LEVEL: 2
CHLORIDES: DRY
CaCO3: DRY
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
• Surface area coated:
5%
• Minimum thickness:
0.00 mils
• Maximum thickness:
0.00 mils
• Maximum pit depth:
0.73 mils
Dickinson County, KS
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated:
0%
• Minimum thickness:
0.00 mils
• Maximum thickness:
0.00 mils
• Maximum pit depth:
37.00 mils
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.107
• INVERT: AVG = 0.122
• 4 o'clock AVG = 0.111
* Avg of a minimum of 4 readings after cleaning measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns):
• TOP: 45
• INVERT: 16
*Avg of a minimum of 4 readings after cleaning
d-f%RA11AER1-r '.
• Scaling at the invert could be cause for increase in thickness measurements
• Pipe is in good condition
• No further corrosion of previous trepan holes
Pratt County, Kansas
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
36" - RIVETED
14 (0.079 IN)
ESTIMATED AT 1953
MAY, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: 7
PH: N/A
RESISTIVITY: 3,290 Q-CM
RESISTIVITY: N/A
FHWA ABRASION LEVEL: 2
CHLORIDES: DRY
CaCO3: DRY
IMAGES:
k�7
I"..
SOIL SIDE ALUMINUM COATING DATA:
0
• Surface area coated:
5%
• Minimum thickness:
0.00 mils
• Maximum thickness:
0.00 mils
• Maximum pit depth:
14.00 mils
J
Pratt County, Kansas
WATER SIDE ALUMINUM COATING DATA:
laT✓ . -.tee .
• Surface area coated:
5%
• Minimum thickness:
0.00 mils
• Maximum thickness:
0.00 mils
• Maximum pit depth:
12.00 mils
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.081
• INVERT: AVG = 0.080
* Avg of a minimum of 4 readings after cleaning measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns
• TOP: 41
• INVERT: 20
*Avg of a minimum of 4 readings after cleaning
d-r%RARALhMC.
• Pipe is in good condition
• No further corrosion of previous trepan holes
Ripley, Maine
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
48"
12 (0.109 IN)
ESTIMATED 1984
JUNE, 2012
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: 6
RESISTIVITY: N/A
RESISTIVITY: N/A
FHWA ABRASION LEVEL: 2
CHLORIDES: N/A
CaCO3: 100
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
WATER SIDE ALUMINUM COATING DATA:
.AL,"kj"4"z1
• Surface area coated:
100%
• Minimum thickness:
0.00
• Maximum thickness:
1.13 (29 µm)
• Maximum pit depth:
2.31 mils
• Surface area coated:
0%
• Minimum thickness:
0.00
• Maximum thickness:
0.00
• Maximum pit depth:
41.00 mils
Ripley, Maine
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP AVG = 0.095
• INVERT AVG = 0.090
* Avg of a minimum of 4 readings after cleaning using TI-25M Ultrasonic Wall Thickness Gauge
COMMENTS:
• Pipe and coating were in good condition
Carter County, Missouri
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
30" - RIVETED
14 (0.079 IN)
ESTIMATED AT 1953
JUNE, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: 6.7
PH: N/A
RESISTIVITY: 1,420 Q-CM
RESISTIVITY: N/A
FHWA ABRASION LEVEL: 1
CHLORIDES: DRY
CaCO3: DRY
SOIL SIDE ALUMINUM COATING DATA:
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated
• Minimum thickness:
• Maximum thickness
• Maximum pit depth
• Surface area coated
• Minimum thickness:
• Maximum thickness
• Maximum pit depth
100
0.00 mils
1.65 mils (42 µm)
0.00 mils
10%
0.00 mils
0.00 mils
10.50 mils
Carter County, Missouri
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.076
• INVERT: AVG = 0.074
* Avg of a minimum of 4 readings after cleaning measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns):
• TOP: 31
• INVERT: 18
*Avg of a minimum of 4 readings after cleaning
COMMENTS-
• Pipe is in good condition
• No further corrosion of previous trepan holes
Bernalillo, New Mexico
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
30"
14 (0.079 IN)
ESTIMATED AT 1952
JUNE, 2012
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: 7.7
PH: DRY
RESISTIVITY: 2,750 Q-CM
RESISTIVITY: DRY
FHWA ABRASION LEVEL: N/A
CHLORIDES: DRY
CaCO3: DRY
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated:
0%
• Minimum thickness:
0.00
• Maximum thickness:
0.00
• Maximum pit depth:
57.00 mils
• Surface area coated:
0%
• Minimum thickness:
0.00
• Maximum thickness:
0.00
• Maximum pit depth:
26.00 mils
Bernalillo, New Mexico
ULTRA -SONIC PIPE THICKNESS ON):
• INVERT AVG = 0.083
* Avg of a minimum of 4 readings after cleaning using TI-25M Ultrasonic Wall Thickness Gauge
COMMENTS:
• Pipe appeared to be in fair condition
• Pipe is too full of silt to perform
Cottage Grove (Anlauf), Oregon
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
66"
12 (0.109 IN)
ESTIMATED AT 1993
MAY, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: 5.0
RESISTIVITY: 2,860 Q-CM
RESISTIVITY: 10,870 ()-CM
FHWA ABRASION LEVEL:
CHLORIDES: <1
CaCO3: 40 - 80 PPM
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
• Surface area coated: 100%
• Minimum thickness: 0.00 mils
• Maximum thickness: 1.87 mils (47.5µm)
• Maximum pit depth: 1.60 mils
Cottage Grove (Anlauf), Oregon
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated: 90%
• Minimum thickness: 0.00 mils
• Maximum thickness: 2.19 mils (55.5µm)
• Maximum pit depth: 11.00 mils
*Note: largest visible pit is a result of the removal process
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.104 (0.104, 0.104, 0.103, 0.103, 0.105)
• INVERT: AVG = 0.106 (0.106, 0.107, 0.108, 0.105, 0.102)
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns
• TOP: 41
• INVERT: 37
*Avg of a minimum of 4 readings after cleaning
rnAAAACNITC-
• Black scaling on the invert
• This is long run of pipe (a few hundred feet) under high fill
Jefferson, Oregon
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
72"
10 (0.0138 IN)
ESTIMATED AT 1993
MAY, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: 5
RESISTIVITY: 8,720 Q-CM
RESISTIVITY: 10,010 Q-CM
FHWA ABRASION LEVEL: 3
CHLORIDES: N/A
CaCO3: 100 PPM
innnr_rc.
SOIL SIDE ALUMINUM COATING DATA:
WATER SIDE ALUMINUM COATING DATA:
Surface area coated
Minimum thickness:
Maximum thickness
Maximum pit depth
Surface area coated:
Minimum thickness:
Maximum thickness:
Maximum pit depth:
I
100 %
1.63 mils
2.36 mils (60 µm)
0.00 mils
60%
0.00 mils
2.78 mils (70 µm)
81.00 mils
*Note: largest visible pit is a result of the removal
process
Jefferson, Oregon
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.119 (0.119, 0.120, 0.117, 0.132, 0.134)
• INVERT: AVG = 0.117 (0.120, 0.115, 0.115, 0.116)
• 9 o'clock position AVG = 0.117 (0.118, 0.117, 0.117)
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns):
• TOP: 56
• INVERT: 69
*Avg of a minimum of 4 readings after cleaning
COMMENTS:
• Pipe is comprised of approximately 160 ft of ALT2 and 60 ft of asphalt coated galvanized at the upstream
end
• Some cracking in the haunch areas of 3 sections appears to be from clay backfill that was used
• Maximum pit depth taken from section where another pilot hole had be started for the trepan evaluation
Santiam Highway 18+20, Oregon
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
301,
16 (0.064 IN)
ESTIMATED AT 1985
APRIL, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: 4.5
RESISTIVITY: 14,300 Q-CM
RESISTIVITY: 55,000 0-CM
FHWA ABRASION LEVEL: 2
CHLORIDES: <2
CaCO3: <40 PPM
SOIL SIDE ALUMINUM COATING DATA:
• Surface area coated:
• Minimum thickness:
• Maximum thickness:
• Maximum pit depth:
100%
0.00 mils
1.45 mils (37 µm)
0.94 mils
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated
• Minimum thickness:
• Maximum thickness
• Maximum pit depth
80%
0.00 mils
2.31 mils (58.5 µm)
1.54 mils
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.051 (0.054, 0.051, 0.055, 0.050, 0.051)
• INVERT: AVG = 0.052 (0.049, 0.056, 0.049, 0.051, 0.052)
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns):
• TOP: 52
• INVERT: 65
*Avg of a minimum of 4 readings after cleaning using DCF3000FX
COMMENTS:
• This is a combination of ALT2 and galvanized pipe with total installation length of approximately
180 ft
San tiam Highway 38+12, Oregon
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
54"
14 (0.079 IN)
ESTIMATED AT 1985
MAY, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: 5.0
RESISTIVITY: 9,440 Q-CM
RESISTIVITY: 23,810 O-CM
FHWA ABRASION LEVEL: 2
CHLORIDES: <2
CaCO3: <40 PPM
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
I
i.
• Surface area coated: 100%
• Minimum thickness: 0.55 mils
• Maximum thickness: 2.28 mils (58 µm)
• Maximum pit depth: 1.35 mils
Santiam Highway 38+12, Oregon
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated:
65%
• Minimum thickness:
0.00 mils
• Maximum thickness:
1.72 mils (43.5µm)
• Maximum pit depth:
4.97 mils
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.067 (0.067, 0.066, 0.069, 0.067, 0.066)
• INVERT: AVG = 0.069 (0.069, 0.073, 0.068, 0.067, 0.068)
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns
• TOP: 46.5
• INVERT: 31
*Avg of a minimum of 4 readings after cleaning
rnAAAACNITC-
• This is a twin pipe barrel installation
• Data collected from the west side where abrasion appeared to be more severe
San tiam Highway 44+50, Oregon
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
30"
16 (0.064 IN)
ESTIMATED AT 1985
MAY, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: 5 - 6
RESISTIVITY: 29,030 O-CM
RESISTIVITY: 23,410 O-CM
FHWA ABRASION LEVEL: 2
CHLORIDES: <1
CaCO3: 0-40 PPM
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
FE
r
• Surface area coated: 100%
• Minimum thickness: 1.00 mils
• Maximum thickness: 3.01 mils (76.5 µm)
• Maximum pit depth: 0.87 mils
1
Santiam Highway 44+50, Oregon
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated:
55%
• Minimum thickness:
0.00 mils
• Maximum thickness:
1.05 mils (26.5 µm)
• Maximum pit depth:
2.28 mils
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.053 (0.052, 0.051, 0.052, 0.055, 0.055)
• INVERT: AVG = 0.051 (0.051, 0.053, 0.050, 0.051, 0.049)
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns):
• TOP: 49
• INVERT: 41
*Avg of a minimum of 4 readings after cleaning
COMMENTS:
• Coating is stained at the invert but in good condition as is the overall pipe
Santiam Highway 90+38, Oregon
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
36"
16 (0.064 IN)
ESTIMATED AT 1985
APRIL, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: 5.5
RESISTIVITY: 14,410 Q-CM
RESISTIVITY: 18,520 O-CM
FHWA ABRASION LEVEL: 3
CHLORIDES: <1
CaCO3: 0-40 PPM
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated
• Minimum thickness:
• Maximum thickness
• Maximum pit depth
• Surface area coated
• Minimum thickness:
• Maximum thickness
• Maximum pit depth
30%
0.00
0.88 (22 µm)
35.50 mils
0%
0.00
0.00
51.50 mils
Santiam Highway 90+38, Oregon
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.055 (0.051, 0.057, 0.055, 0.055, 0.056)
• INVERT (@ 8 o'clock position): AVG = 0.051 (0.048, 0.051, 0.056, 0.050, 0.052)
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns):
• TOP: 35
• INVERT: 37
*Avg of a minimum of 4 readings after cleaning using DCF3000FX
COMMENTS-
• This is a twin barrel installation where both culverts appear to experience high velocity abrasive flow
Santiam Highway 100+15, Oregon
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
30"
16 (0.064 IN)
ESTIMATED AT 1985
MAY, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: 5
RESISTIVITY: 14,350 O-CM
RESISTIVITY: 28,570 Q-CM
FHWA ABRASION LEVEL: 1
CHLORIDES: <1
CaCO3: 0-40 PPM
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
• Surface area coated: 100%
• Minimum thickness: 0.87 mils
• Maximum thickness: 1.42 mils (36 µm)
• Maximum pit depth: 3.38 mils
Santiam Highway 100+15, Oregon
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated:
95%
• Minimum thickness:
0.00 mils
• Maximum thickness:
1.66 mils (42 µm)
• Maximum pit depth:
5.00 mils
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.051 (0.050, 0.050, 0.052, 0.051, 0.051)
• INVERT: AVG = 0.049 (0.047, 0.051, 0.051, 0.048, 0.049)
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns):
• TOP: 49
• INVERT: 29
*Avg of a minimum of 4 readings after cleaning
COMMENTS:
• The pipe appears to be in good condition
• There is no pavement distress
• The total length of the installation is approximately 66 ft
Santiam Highway 104+45 East & West, Oregon
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
71" X 47" ARCH PAIR
10 (0.0138 IN)
ESTIMATED AT 1985
MAY, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: 5
RESISTIVITY: 14,700 Q-CM
RESISTIVITY: 32,258 Q-CM
FHWA ABRASION LEVEL: 3
CHLORIDES: <1
CaCO3: 0-40 PPM
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
• Surface area coated: 100%
• Minimum thickness: 0.93 mils
• Maximum thickness: 2.09 mils (S3 µm)
• Maximum pit depth: 1.16 mils
*Note: largest visible pit is a result of the removal process
Santiam Highway 104+45 East & West, Oregon
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated:
10%
• Minimum thickness:
0.00 mils
• Maximum thickness:
0.00 mils (42 µm)
• Maximum pit depth:
20.00 mils
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.135 (0.136, 0.135, 0.136, 0.132, 0.134)
• INVERT: AVG = 0.139 (0.139, 0.137, 0.141)
• Splash Zone (@ 5 o'clock position) AVG = 0.134 (0.135, 0.135, 0.134, 0.134, 0.134)
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
**Readings taken from east pipe
COATING THICKNESS COMPARISON (microns):
• TOP: East = 33 West = 38
• INVERT: East = 9 West = 14
*Avg of a minimum of 4 readings after cleaning
COMMENTS:
• This is a twin barrel installation where the west pipe appears to receive heavier and faster flow
due to the approach angle
• Data presented is from both pipe barrels
Santiam Highway 123+76, Oregon
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
36"
16 (0.064 IN)
ESTIMATED AT 1985
APRIL, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: 5.0
RESISTIVITY: 31,460 Q-CM
RESISTIVITY: 27,780 O-CM
FHWA ABRASION LEVEL: 2
CHLORIDES: <1
CaCO3: 0-40 PPM
SOIL SIDE ALUMINUM COATING DATA:
• Surface area coated:
100%
• Minimum thickness:
0.00 mils
• Maximum thickness:
1.07 mils (27 µm)
• Maximum pit depth:
1.20 mils
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated: 100%
• Minimum thickness: 0.00 mils
• Maximum thickness: 1.46 mils (37 µm)
• Maximum pit depth: 1.13 mils
*Note: largest visible pit is a result of the
removal process
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.055 (0.052, 0.057, 0.058, 0.055, 0.053)
• INVERT: AVG = 0.056 (0.056, 0.060, 0.059, 0.052, 0.056)
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
P1^R A R A C I.ITC.
• Pipe is in good condition
• No pavement distress
• Total installation length is approximately 80 ft.
Santiam Highway New Site 1, Oregon
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
30"
16 (0.064 IN)
ESTIMATED AT 1985
APRIL, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: DRY
RESISTIVITY: 14,470 Q-CM
RESISTIVITY: DRY
FHWA ABRASION LEVEL: 1
CHLORIDES: DRY
CaCO3: DRY
IMAGES:
SOIL SIDE ALUMINUM COATING DATA:
• Surface area coated: 100%
• Minimum thickness: 0.55 mils
• Maximum thickness: 3.04 mils (77 µm)
• Maximum pit depth: 1.60 mils
Santiam Highway New Site 1, Oregon
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated: 95%
• Minimum thickness: 0.37 mils
• Maximum thickness: 1.584 mils (40 µm)
• Maximum pit depth: 0.67 mils
*Note: largest visible pit is a result of the removal process
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.057 (0.060, 0.059, 0.055, 0.055, 0.056)
• INVERT: AVG = 0.058 (0.059, 0.054, 0.056, 0.061, 0.058)
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns):
• TOP: 38
• INVERT: 29
*Avg of a minimum of 4 readings after cleaning using DCF3000FX
COMMENTS:
• Pipe in good condition
• No pavement distress
Santiam Highway New Site 2, Oregon
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
301,
16 (0.064 IN)
ESTIMATED AT 1985
APRIL, 2013
PROFILE
COATING
SOIL DATA
WATER DATA
2 2/3 X 1/2
ALUMINIZED TYPE 2
PH: N/A
PH: DRY
RESISTIVITY: 18,590 Q-CM
RESISTIVITY: DRY
FHWA ABRASION LEVEL: 1
CHLORIDES: DRY
CaCO3: DRY
SOIL SIDE ALUMINUM COATING DATA:
• Surface area coated:
• Minimum thickness:
• Maximum thickness:
• Maximum pit depth:
100%
0.94 mils
2.18 mils (55 µm)
1.02 mils
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated
• Minimum thickness:
• Maximum thickness
• Maximum pit depth
95%
0.00 mils
2.03 mils (51.5 µm)
9.00 mils
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP: AVG = 0.051 (0.051, 0.050, 0.051, 0.056, 0.056)
• INVERT: AVG = 0.055 (0.051, 0.055, 0.055, 0.056, 0.056)
*Measured using TI-25M Ultrasonic Wall Thickness Gauge
COATING THICKNESS COMPARISON (microns):
• TOP: 32
• INVERT: 32
*Avg of a minimum of 4 readings after cleaning using DCF3000FX
Memrancook, New Brunswick, Canada
DIAMETER
GAGE
YEAR INSTALLED
INSPECTION DATE
72"
12 (0.109 IN)
ESTIMATED 1996
JUNE, 2012
PROFILE
COATING
SOIL DATA
WATER DATA
5 X 1
ALUMINIZED TYPE 2
PH: N/A
PH: 6
RESISTIVITY: N/A
RESISTIVITY: N/A
FHWA ABRASION LEVEL: 2
CHLORIDES: N/A
CaCO3: D100
IMAGES:
SN�
SOIL SIDE ALUMINUM COATING DATA:
WATER SIDE ALUMINUM COATING DATA:
• Surface area coated:
100%
• Minimum thickness:
0.00
• Maximum thickness:
3.02 (76.5 µm)
• Maximum pit depth:
0.78 mils
• Surface area coated:
100%
• Minimum thickness:
0.83
• Maximum thickness:
2.54 (64.5 µm)
• Maximum pit depth:
1.55 mils
Memrancook, New Brunswick, Canada
ULTRA -SONIC PIPE THICKNESS (IN):
• TOP AVG = 0.095
• INVERT AVG = 0.092
* Avg of a minimum of 4 readings after cleaning using TI-25M Ultrasonic Wall Thickness Gauge
COMMENTS:
• Pipe and coating in good condition
• Pipe has baffles installed in the invert
Appendix B - Recommended Inspection Procedure
18
TOOLS
This list could vary depending on the scope of the assessment. For instance, if the objective is only to
show the remnant pipe thickness, this list could be reduced to the first seven items:
• Project inspection notebook — recommend a permanently bound book with numbered pages
that is used only for on -site comments, raw data collection and site location information.
• Ultrasonic thickness gauge and coupling gel, scotch -bright pads, paper towels
• Representative reference coupon(s) - see section on calibration
• Digital Camera
• DCF 3000FX coating thickness gauge is used to measure the thickness of non-magnetic coatings
on ferrous substrates. This is not a calibrated instrument; it only measures and compares water-
side metallic coating thickness. A useful comparison results when performed near the invert and
the crown.
• Quart size zip-loc freezer bags for representative soil samples
• 250 ml sample bottles for water samples
• Shovel, Garden Spade, Machete or sickle
• pH paper (Hatch)
• Hand cleaner, insect repellant, bottled water and more paper towels
• If you plan to cut core samples from the pipes, you will need:
o 18V (or stronger) cordless drill, 1.5" diameter hole saw(s),%" drill bits, center punch,
hammer, spare battery pack, charger, power inverter that plugs into a cigarette lighter.
*After one site inspection, the reader will likely be able to modify this list as necessary.
CALIBRATION
It is recommended to use a reference coupon of Type 2 that is comparable in thickness to the pipe being
inspected. Most projects are made of 16, 14, 12 or 10 gauge material or 0.064", 0.079", 0.109" or 0.138"
nominal thickness, respectively. A flat -head micrometer that has been calibrated using standards that
are traceable to NIST should be used to measure the thickness of the reference coupons. This thickness,
scribed onto the coupon, can then be used to verify / standardize the ultrasonic thickness gauge in the
field prior to each use. The reference coupons should be sheathed to protect them from abrasion or
rough handling and carefully packed along with the ultrasonic thickness gauge. Data and comments
referencing field calibration results should be entered into the project inspection notebook.
PROCEDURES
To measure the remaining pipe thickness after a number of years of service, enter the title and location
of the project via map, GPS, or driving instructions in the inspection book.
The ultrasonic thickness gauge should be field calibrated (inspection notebook entry) and the surfaces to
be measured should be wiped clean of debris, thus allowing firm steady contact of the probe head and
the pipe surface. Gentle repetitive rubs with a scotch -bright pad will easily remove any crust or debris
from the metallic coating, followed by cleaning with a paper towel.
Photograph the freshly cleaned metallic coating at/near the invert to document the coating condition.
Take digital images documenting the project's location, and thickness testing positions.
Take and record multiple thickness readings at/near the crown and at/near the invert. The writer
recommends a minimum of three if there is agreement (less than 0.002" or 0.05mm variation between
the highest and lowest reading).
If the corrugations are annular, then thickness testing should be on the flatter upstream portion of the
annular corrugation. If the pipe is spiral rib, then the large flat regions should be representative.
In the inspection notebook, write down the condition of the upstream -facing edge of the spiral ribs;
whether abraded, pitting or smooth. Record these observations and ultrasonic thickness readings and
average this raw data in the inspection notebook. Take digital images to support the comments
recorded.
The crown of the pipe is assumed to represent the pipe's original thickness. The difference between the
average thicknesses (crown vs. invert) would represent the material consumed during the years of
service.
If the surfaces at the invert and crown have aluminized coating intact, use the DCF-3000FX to compare
the thickness of the metallic coatings on the water side of the pipe. Several rubs with a scotch -bright
may be needed to remove buildup on the coating near the invert to determine if metallic coating
remains.
Water (if available) and soil samples be collected and labeled by site. The soil sample should be
representative of the backfill in contact with the soil side of the pipe. These should submitted to an
independent lab with the credentials to test the soil and water for pH, resistivity (units: ohm -cm) and
test for the presence of sulfates (ppm) and chlorides (ppm).
If the inspector plans to procure coupons, the following instructions are subordinate and
complementary to normal safety procedures that govern work involving power tools at remote locations
outlined by the inspector's employer.
Select a representative location as near to the invert as possible/practical. Use the hammer and center
punch to designate a starting point to drill. If the pipe is annular, select a peak, if it is spiral rib, select a
flat adjacent to the rib in order to represent that portion of the spiral rib that faces upstream.
Drill a X" hole first, then install the hole saw equipped with a solid center shaft (1/4" diameter) where
the drill bit would go. This technique will prevent breaking drill bits in the hole saw while drilling cores in
steel pipe. This two -stage practice may seem time consuming, but changing broken drill bits on a hole
saw or running out of drill bits in the field is much more time consuming.
Remove the core from the hole saw, label the downstream portion and insert in a labeled bag. These
cores can be measured, photographed and mounted metal lographically to assess the condition of the
metallic coating.
SUMMARY
The recommended procedures for measuring pipe wall and coating thickness, sampling soil and water
and recording representative images of a project should be done objectively such that an independent
observer could repeat the same steps and arrive at comparable conclusions. These summaries should be
beneficial for promoting Aluminized Type 2 CSP because the data collected is from sites with more
regional significance or environmental relevance to the owners and engineers responsible for
establishing project material specifications. If pipes are failing prematurely then the information
gathered can help establish the failure mode.