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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. //

Talk to the Editor: Maryann Gorman

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

One of the most serious infrastructure problems is corrosion of steel in concrete. This is evident in the over 200,000 federal bridges needing repairs in excess of $50 billion, and in numerous parking and marine structures. Subcommittee G01.14 is actively involved in developing and maintaining test methods to address this corrosion issue. As steel is embedded in opaque concrete it is difficult to assess performance until cracking, spalling, and staining of the concrete are visible. The most widely used technique in the world to electrochemically assess hidden corrosion performance for steel in concrete is ASTM C 876, Test Method for Half-Cell Potentials of Uncoated Reinforcing Steel in Concrete, which is currently being revised in the subcommittee.
ASTM Committee G-1’s standards for corrosion control are among the most-used in many industries, including chemical processing, automotive, and marine/ offshore industries.

The committee has recently become a “classified” ASTM committee, making it possible for the group to write specifications.

Cynthia Greenwood is a freelance writer and consultant based in Houston, Texas. She worked as an editor for NACE International, The Corrosion Society, is a contributing writer for the Houston Press, and is an adjunct faculty member at Wharton County Junior College.