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Feature
ASTM Standards to Prevent
Corrosion Prevail in a Dynamic
Business and Regulatory
Environment
by Cynthia Greenwood
Corrosion cost the nation $300 billion in 1995. In the average
household, it attacks everything from gas lines and water pipes
to the shiny exterior of the family car. When roads and foundations
collapse in your neighborhood, corrosion is often the insidious
culprit. It’s the number-one threat to America’s aging infrastructure,
sabotaging underground pipelines, parking garages, bridges, railroads,
and water distribution systems. Not even the Statue of Liberty
and other precious landmarks can escape its deteriorating forces.
Corrosion also plagues American industry. It must be reckoned
with in a host of commercial processes, from manufacturing paper
and chemicals to drilling for oil and gas offshore. It even disturbs
telephone and electric power systems. In every sector where corrosion
is imminent, there’s a potential threat to public health and safety.
But since the 1964 formation of ASTM Committee G-1 on Corrosion
of Metals, the committee has been quite successful in providing
standards that serve as weapons in industry’s war against corrosion.
Recently, the committee has placed more emphasis on industry-specific
standards. To meet the demand, the committee is considering realigning
itself to better meet industry sectors’ needs and has stepped
up its collaboration with outside groups. A look at these partnerships
and ways in which established ASTM corrosion standards are beneficial
to the chemical, automotive, and marine/offshore industry in light
of new business trends and environmentally friendly products follows.
The Chemical Processing Industry
Two notable trends have taken shape in the corrosion-control arena
of the chemical processing industry: the elimination of redundant
tests as well as the preference for certain ASTM corrosion standards
over proprietary methods. Large chemical companies typically require
stainless steel and nickel-base alloys to be tested for resistance
to intergranular corrosion and localized corrosion using G-1 standards
on detecting susceptibility to intergranular corrosion and evaluating
stress corrosion cracking resistance.1,2 Because of reduced staffs,
they are moving away from conducting acceptance tests, and instead,
rely on the equipment manufacturers to do the tests.
Galen Hodge, marketing vice president at Haynes International,
an Indiana-based alloy producer, sees the shift. “Our customers
are getting away from having to reproduce every test that we do.
They are putting more requirements on the producers and auditing
them periodically to ensure quality control, but without doing
the over-checks they used to do,” he says.
Some large companies also required suppliers to perform intergranular
corrosion tests on alloys based on their own in-house guidelines.
Five years ago, DuPont moved away from using in-house guidelines
after Dr. Michael Streicher (now retired from DuPont) spearheaded
the writing of an ASTM intergranular corrosion test method. The
company eventually substituted ASTM’s method for its own specifications.
Some experts swear by ASTM standards because they provide quick,
reliable answers. Sheldon Dean, head of the Materials and Corrosion
Group at Air Products and Chemicals, recalls how the slow strain
rate test3 explained a mysterious bypass pipe explosion that caused
fire and equipment damage at a hydrogen manufacturing plant in
1996. Dean was surprised when he learned the pipe failed due to stress corrosion cracking
(SCC), since the syngas4 environment in which the pipe failed
seemed unlikely to produce SCC.
To get to the root of the problem, the company had stainless steel
(type 304L) and a low-alloy steel in potassium hydroxide (KOH)
solutions tested for susceptibility to SCC.5 Using the slow strain
rate test, the lab learned that KOH originating from a potassium-promoted
catalyst entered the bypass pipe in question during startup conditions.
“The advantage of the G 129 method was that it allowed us to test
50 or 60 test specimens and get the answer [to each test] in two
days,” Dean says. The method’s quick results saved the company
money, revealed the source of the failure, and provided the means
to preventing similar, potentially life-threatening problems from
recurring at other plants.
Dean believes G-1 standards such as the slow strain rate test,
the practice for making U-bend test specimens,6 and the procedure
for testing alloys in high temperatures or pressures7 are preferred
because they allow users to predict the type of variation one
can expect from the results. “[ASTM standards] give you a way
to set reasonably high, though not impossible standard requirements,”
he says. Dean feels ASTM methods are also beneficial because companies
like his can easily hire a third party to perform the test and
not have to worry about getting reliable results.
To ensure that ASTM laboratory standards are in line with corrosion
experts’ experience, G-1 committee members began collaborating
with researchers at the Materials Technology Institute (MTI) five
years ago. MTI found it difficult to compare the results of existing
test methods on the carburization process, because they were so
different. So they developed what they felt were the best procedures.
Soon afterwards, the G-1 subcommittee handling laboratory corrosion
testing began adapting the MTI guidelines into new standards that
will lend themselves to a direct comparison of data.
Automotive Industry
Recent trends in keeping automobiles corrosion-free has been driven
by the changing face of the automotive industry. Gone are the
days when automakers depended solely on their own labs to conduct
a battery of tests on body panels and exhaust systems. Now they
rely on steel producers and major paint companies to perform qualified
tests, or farm the work out to independent labs.
Within the Body Materials Engineering and Corrosion Testing division
at DaimlerChrysler, Dominick Bologna says his company is spending
more money, not less, on corrosion testing. “The customer demands
more. There is more competition. We see requirements increasing
for many types of tests in order to ensure the product is improving,
as well as the need to find where improvements can be made.” There
are lean times, he admits, when the company outsources specific
duties to independent testing labs. “Suppliers are encouraged
to have in-house labs,” he adds.
As a steel supplier to the industry, Bethlehem Steel’s Herbert
Townsend sees a parallel trend. “Auto makers are requiring suppliers
to do the type of testing they want done and asking them to do
more testing.” He says automakers ensure quality control by demanding
high quality standards for corrosion testing from their suppliers.
Today, suppliers can fulfill high standards by meeting the auto
maker’s own accreditation requirements or the rules of the American
Association for Laboratory Accreditation.
According to Robert Baboian, a corrosion consultant, over the
past three decades, the industry has relied on dozens of ASTM
standards to develop and test corrosion-resistant alloys and coatings
for auto exhaust systems, chassis, engine components, electronics,
trim, and body panels. To test paints and platings, DaimlerChrysler
uses the ASTM salt spray test8 and the cyclic corrosion test9
in addition to standards developed by the Society of Automotive
Engineers (SAE), Bologna says.
Sean Brossian, research engineer at the Southwest Research Institute
and chairman of NACE’s automotive corrosion committee, confirms
that materials manufacturers use ASTM corrosion standards to test
metals and alloys for resistance to pitting and crevice corrosion10
and to define how they perform in weather11 and moisture containing
sulfur dioxide.12 OEMs also rely on the cyclic humidity test,13
the electrochemical procedure for testing localized corrosion
resistance,14 and two methods for evaluating weld corrosion on
exhaust systems.15,16
For many years, auto makers and coatings manufacturers have depended
on the salt spray test as one step in a user’s comprehensive corrosion-control assessment program
for coated and non-coated materials. In general, while it is felt
that the salt spray test is a good tool for quality assurance
testing and in some cases comparing similar materials, the need
for a test that relates to exposures in real environments is apparent.
To meet that need, G-1 plans work on a Guide for Laboratory Cyclic
Corrosion Tests, which will reference a standard developed by
SAE17 that controls for temperature, humidity, and salt, and is
designed to measure a material’s performance on a vehicle.
The Marine/Offshore Industry
Both commercial and military interests drive corrosion testing
in marine and offshore environments. Mergers in the offshore oil
and gas industry over the last five to 10 years have resulted
in reduced funds to test coatings. Giants such as BP-Amoco and
Mobil rely on veteran paint manufacturers to perform corrosion
tests for applications offshore.
“It used to be that every company had someone who was doing coatings
testing,” said Peter Treleaven, special projects manager at Hempel
Coatings. “The mergers changed all that. There are some companies
that aren’t doing extensive testing but are relying on qualified
coatings companies that have been in business for a long time.”
At Ameron’s office in Brea, California, principal chemist Judy
Cheng says the customers determine the corrosion test methods
she uses. Large oil companies often evaluate their own coatings
for offshore applications based on their own protocol, Cheng says.
The military requires Ameron to adapt to its test methods. Other
customers demand that Ameron conduct third-party lab tests based
on customized procedures. “It all depends on how the customer
wants to get involved.”
Cheng’s division commonly uses ASTM standards to test household
paints for hardness.18,19 Ameron relies on ASTM procedures to
test the adhesion properties in industrial paints.20 “If a [test
method] is based on ASTM, it’s easy to find a third party to run
it,” she says. Ameron also depends on ASTM’s test for coatings
used in conjunction with cathodic protection21 around ship ballast
tanks, cargo holds, and other marine applications.
To supply industrial paint products for marine and railcar industries,
Sigma Coatings, a Dutch-owned subsidiary of Fina Total, frequently
uses the salt spray and cyclic corrosion tests according to the
needs of U.S. customers. “We look at ISO and other overseas standards
for some methods for which ASTM has no equivalent. But as long
as our customers are more familiar with ASTM than ISO, we’ll go
ahead and do the test according to ASTM,” says Max Winkeler, consultant
and former vice president of research and development.
As a leading paint provider for immersed surfaces in the shipbuilding
industry, Norwegian-based Hempel coatings relies on U.S. Navy
mandates as well as ASTM procedures. It relies on ASTM to verify
a coating’s hardness,18,19 adhesion,20 and weatherability.8,22
“ASTM procedures and guidelines are the backbone of our industry,”
says Muhammad Jamil, vice president of research and development.
“We have to sell the technology under a standard set of rules.”
G-1 Responds to Regulatory and Conservation Concerns
Since the EPA restricted the use of heavy metals and volatile
organic compounds (VOCs) under the Clean Air Act of 1977, corrosion-control
materials and test methods have radically altered. Rules governing
hazardous air pollutants (HAPs) are still changing. Military and
commercial researchers are inventing non-toxic conversion coating
processes and paint systems to make marine, plant, and architectural
structures corrosion-resistant.
Vinod S. Agarwala, a senior scientist at the Naval Air Warfare
Center’s Aircraft Division, has patented NAVARCO-818™ materials
for use in a Trivalent Chromium Conversion Coating Process™ for
treating aluminum horizontal and vertical tail surfaces as well
as sections behind the fuselage. The new process, which uses chromium
III, is less toxic and equally as effective as hazardous chromate
conversion coatings using chromium VI. It also allows for simpler,
more economical waste treatment.
ASTM has a variety of cabinet tests that can be used to compare
chromium III to chromium VI products in atmospheric exposures8,
12, 23, 24 as well as guidelines for recording data from the tests.24,
25 To compare chromium III to chromium VI for underwater exposures,
users can employ G-1 standards for field testing,26 seawater testing,27
laboratory immersion testing,28 and crevice corrosion testing.29
Conclusion
For over 35 years, Committee G-1 has helped limit what would otherwise
be corrosion’s slow but sure degradation of our nation’s infrastructure.
In key industries, G-1’s standards are often the most-trusted
and relied-upon tests and practices a company can use for quality
assurance and other corrosion-related needs. As the 21st century
begins, and as the needs of the corrosion-control community change,
G-1 plans to gear its standards development activities even more
toward the needs of key industry
sectors. //
References:
1 G 28, Standard Test Methods of Detecting Susceptibility to Intergranular
Corrosion in Wrought, Nickel-Rich, Chromium-Bearing Alloys
2 G 44, Standard Practice for Evaluating Stress Corrosion Cracking
Resistance of Metals and Alloys by Alternate Immersion in 3.5%
Sodium Chloride Solution
3 G 129, Standard Practice for Slow Strain Rate Testing to Evaluate
the Susceptibility of Metallic Materials to Environmentally Assisted
Cracking
4 A mixture of hydrogen, carbon monoxide, carbon dioxide, methane,
and steam.
5 Sheldon Dean, “Caustic Cracking from Potassium Hydroxide in Syngas,”
Materials Performance, January 1999, p. 74.
6 G 30, Standard Practice for Making and Using U-Bend Stress-Corrosion
Test Specimens
7 G 111, Standard Guide for Corrosion Tests in High Temperature
or High Pressure Environment, or Both
8 B 117, Standard Practice for Operating Salt Spray (Fog) Apparatus
9 D 5894, Standard Practice for Cyclic Salt Fog/UV Exposure of
Painted Metal (Alternating Exposures in a Fog/Dry Cabinet and
a UV/Condensation Cabinet)
10 G 48, Standard Test Methods for Pitting and Crevice Corrosion
Resistance of Stainless Steels and Related Alloys by Use of Ferric
Chloride Solution
11 G 50, Standard Practice for Conducting Atmospheric Corrosion
Tests on Metals
12 G 87, Standard Practice for Conducting Moist SO2 Tests
13 G 60, Standard Test Method for Conducting Cyclic Humidity Tests
14 G 61, Standard Test Method for Conducting Cyclic Potentiodynamic
Polarization Measurements for Localized Corrosion Susceptibility
of Iron-, Nickel-, or Cobalt-Based Alloys
15 A 262, Standard Practices for Detecting Susceptibility to Intergranular
Attack in Austenitic Stainless Steels
16 A 763, Standard Practices for Detecting Susceptibility to Intergranular
Attack in Ferritic Stainless Steels
17 SAE J-2334, New Cyclic Test for Cosmetic Corrosion, Society of
Automotive Engineers
18 D 4366, Standard Test Methods for Hardness of Organic Coatings
by Pendulum Damping Tests
19 D 3363, Standard Test Method for Film Hardness by Pencil Test
20 D 4541, Standard Test Method for Film Hardness by Pencil Test
21 G 8, Standard Test Methods for Cathodic Disbonding of Pipeline
Coatings
22 D 5894, Standard Practice for Cyclic Salt Fog/UV Exposure of
Painted Metal, (Alternating Exposures in a Fog/Dry Cabinet and
a UV/Condensation Cabinet)
23 G 85, Standard Practice for Modified Salt Spray (Fog) Testing
24 G 33, Standard Practice for Recording Data from Atmospheric Corrosion
Tests of Metallic-Coated Steel Specimens
25 G 46, Standard Guide for Examination and Evaluation of Pitting
Corrosion
26 G 4, Standard Guide for Conducting Corrosion Coupon Tests in Field
Applications
27 G 52, Standard Practice for Exposing and Evaluating Metals and
Alloys in Surface Seawater
28 G 31, Standard Practice for Laboratory Immersion Corrosion Testing
of Metals
29 G 78, Standard Guide for Crevice Corrosion Testing of Iron-Base
and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing
Aqueous Environments
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