Combating Corrosion
The evening news may leave many of us feeling war-weary, but one ASTM International technical committee (formerly American Society for Testing and Materials) has been successful in conflict of a different sort. It’s a commonplace but epic struggle between the natural and civilized worlds — the fight against metal corrosion. For the past half-century, the weapon of choice of ASTM Committee G01 on Corrosion of Metals has been its nearly 100 standards. They promote research, the collection of engineering data, and methods and tests for detecting, monitoring, measuring and preventing metal corrosion. While some battles have been won, it’s a sure bet that committee work will continue for many more years. “Corrosion is a part of life,” says Daniel Crabtree, G01 committee chairman and senior project manager, Corrpro Companies Inc., Birmingham, Alabama. “It’s always going to be here.”
We all experience everyday corrosion skirmishes with old, rusting garden tools, overzealously cleaned griddles, bicycles that have never seen the inside of a garage, and cars that have encountered too much melting snow and road salt. More deadly corrosion disasters can involve the failure of power plants, bridges, buildings, silos, vessels, pipes and other infrastructure. In addition to human loss, corrosion can cause environmental harm, contamination, mechanical damage and deterioration of surface properties, like electrical conductivity.
The costs are staggering. According to Robert Baboian, veteran ASTM member and corrosion consultant, Greenville, Rhode Island, a 1976 study by the National Bureau of Standards (now the National Institute of Standards and Technology) determined that the economic effects of corrosion totaled $70 billion annually. By 2002, the U.S. Highway Administration had bumped that figure to $276 billion. NACE International (formerly the National Association of Corrosion Engineers) estimated that the annual cost of corrosion in the United States in 2013 would significantly exceed that amount. Estimates by reputable organizations have put the annual cost of corrosion at $1 trillion worldwide.
A Tactical Approach
With a few exceptions, like gold, most metals do not occur naturally. We process them from ores. As soon as they are used in an environment with oxygen (usually from the atmosphere) and an electrolyte (usually water and/or soil), they strive to break down and return to their elemental form. In a spontaneous and electrochemically biased process, metals behave like deteriorating anodes, employing 15 different types of corrosion as allies. Meanwhile, we counter attack by modifying their environment or using alloys. We provide cathodic protection with galvanic anodes (like zinc) that sacrifice themselves to protect underlying metals or are protected themselves via electrical current. Or we introduce corrosion inhibitors, like coatings or platings.
“The corrosion process is an insidious one, which is often difficult to recognize until extensive deterioration has occurred. In some cases, this leads to catastrophic failure,” notes Baboian.
Committing to Combat
As early as 1900, ASTM members were concerned about corrosion. Railroads wanted reliable track. Steel’s ability to withstand corrosion versus wrought iron was a popular subject of debate. By mid-century — with increased use of galvanized and stainless steel, plus nonferrous metals like aluminum, nickel and copper — dozens of ASTM subcommittees were formed to consider corrosion. But it was Frances L. LaQue, president of ASTM from 1959 to 1960 and director of marketing at International Nickel Company, who was instrumental in establishing ASTM Committee G01 in 1964. The intent was to reduce duplication of effort, centralize corrosion standards development in one technical committee and acknowledge the growing needs of several industrial sectors.
Escalating Casualties
According to Sheldon Dean, Dean Corrosion Technology, Glen Mills, Pennsylvania, by the mid-1960s, the automobile industry was struggling with pitting and peeling chrome bumpers and corroded painted auto body steel where stainless steel was attached to it. The nuclear power industry needed ways to test for stress corrosion cracking. The chemical industry required solutions for localized corrosion at welds in pipelines. The defense industry wanted to test for the alloys’ tendency to peel off the surfaces of military aircraft. Additionally, with the expansion of the aluminum industry, standard methods were needed to determine the corrosion resistance of aluminum alloys. NASA has been consumed with addressing this pervasive problem for very expensive equipment used in the space program.
With the profusion of industries and applications affected by corrosion, ASTM Committee G01 continued to expand. Today, it has more than 600 members representing 32 countries, and 12 subcommittees with jurisdiction over close to 100 standards used throughout the world.
Standards Development
The committee initially acquired four existing ASTM standards and focused on atmospheric and laboratory tests, plus corrosion in natural water, soils, and industrial and high temperature environments. In recent years, it has published more industry-specific standards geared to the development of new alloys and materials systems for specific environments, notes Baboian. G01 standards address localized corrosion; galvanic corrosion; pitting and crevice corrosion; inter-granular corrosion; and electrochemical techniques for corrosion testing and evaluation.
Future Strategies
Many more years of work remain for ASTM Committee G01. Existing standards continually require revision to keep up with new materials and technology. And new standards are under development. One is in response to requests from auto, truck and vehicle parts manufacturers, and the U.S. Department of Transportation, for more accurate corrosion testing of calcium chloride and magnesium chloride, de-icers used as alternatives to more common road salt, or sodium chloride. Future standards may address non-metallics, such as carbon and composite materials, or corrosion in electronic products, electric cars, wind generators, solar panels or medical products, including stents and joint replacements.
Dean concurs that “very little in the corrosion field is new. We simply aren’t always using the available information to deal with it.” That fact remains part of the endless struggle against corrosion. “Corrosion control needs to be addressed up front,” says Crabtree. “We’ve made great strides in educating the public and industry about corrosion and maintaining infrastructure, but we’ve still got a long way to go.” And the development of standards will continue to be an effective and essential strategy.