SELECTED ABSTRACTS EFFECTS OF CHEMICAL COMPOSITION ON THE ATMOSPHERIC CORROSION RESISTANCE OF LOW-ALLOY WEATHERING STEELS, SUCH AS CORTEN ________________________________________________________________________   REFERENCE: Townsend, H. E., "Estimating the Atmospheric Corrosion Resistance of Weathering Steels," Outdoor Atmospheric Corrosion, ASTM STP 1421, H. E. Townsend, Ed., American Society for Testing and Materials, West Conshohocken, PA, 2002. Abstract: Although important properties such as strength, toughness, and weldability can be easily measured in the laboratory, there is no generally accepted laboratory test for determining the atmospheric corrosion resistance of low-alloy weathering steels. Because many years of outdoor testing are needed to develop corrosion data, there is a need for reliable methods of estimating corrosion performance. The relative corrosion resistance of weathering steels can be estimated from the corrosion index calculated from composition by use of the ASTM Standard Guide for Estimating the Atmospheric Corrosion Resistance of Low-Alloy Steels (G 101). This paper describes a new, alternate method for estimating corrosion resistance from composition that has been recently added to G 101. The new method involves calculation of a corrosion index based on historical data recently published by Bethlehem Steel. It overcomes several limitations of the original G 101 corrosion index. Specifically, more elements are considered. In addition to the five elements (copper, nickel, phosphorus, chromium, and silicon) considered in G 101, the new method also takes account of the effects of several other elements, including carbon, molybdenum, sulfur, and tin. Because the method is based on data from three test sites, as compared to only one site for G 101, the results should be applicable to a wider range of environmental conditions. Also, the ranges of the elements are generally larger than those of G 101. Finally, the effects of the elements increase monotonically. As a result, the new method is free of anomalies resulting from quadratic terms, such as a maximum effect of copper at about 0.25% that is predicted by G 101. The overall absence of quadratic terms allows for more reliable extrapolation beyond the ranges of the original data. To facilitate computation of the G 101 corrosion indices, a Standard G101 Calculator is available under "Additional Information" at the ASTM Committee G01 Page . ESTIMATING THE DURABILITY OF GALVANIZED COATINGS ON STEEL ___________________________________________________________ REFERENCE: H. E. Townsend, Estimating the Life of Galvanized Coatings on Steel Sheet, Materials Performance, 45(3), 30-32, 2006. Flat, horizontal coupons of galvanized steel sheet exposed to outdoor atmospheres corrode faster on the top surfaces than on the bottom surfaces. The coating fails first on the top side, and the time to first rust is determined by the upper rate. Most corrosion rates reported in the literature are calculated from the total loss on both surfaces. The resulting corrosion rates are an average of top and bottom rates. Use of the average rate to calculate coating life leads to overestimates of 20 to 80%. Thus, estimates of galvanized coating life based on flat coupon corrosion rates should be reduced accordingly.     ATMOSHERIC CORROSION BEHAVIOR OF GALFAN COMPARED TO GALVANIZED STEEL ________________________________________ REFERENCE: H.E. Townsend, "Atmospheric Corrosion Resistance of Steel Sheet Coated with 55 Al-Zn Plus Mischmetal," Materials Performance, 44(11), 26-31, 2005. Abstract: Steel sheet with an alloy coating composed of 5% Al-Zn plus a trace of mischmetal (5% Al-Zn + MM) is reported to be more resistant to atmospheric corrosion than conventional galvanized sheet. This article gives the results of 12 years of outdoor corrosion testing in severe marine, moderate marine, industrial, and rural environments. These results indicate that there is no significant difference between the atmospheric durability of 5% Al-Zn + MM and a conventional galvanized coating of the same thickness.

TWENTY-ONE-YEAR ATMOSPHERIC CORROSION TESTS OF GALVALUME, GALVANIZED, AND ALUMINUM-COATED STEEL SHEET BY ASTM ________________________________________________________________________ REFERENCE: Townsend, H. E., and Lawson, H. H., "Twenty-One Year Results for Metallic-Coated Steel Sheet in the ASTM 1976 Atmospheric Corrosion Tests," Outdoor Atmospheric Corrosion, ASTM STP 1421, H. E. Townsend, Ed., American Society for Testing and Materials, West Conshohocken, PA, 2002. Abstract: In 1976, the ASTM G01.04 Subcommittee on Atmospheric Corrosion initiated a long-term atmospheric corrosion test program at five outdoor locations: Kure Beach, NC (25-meter East-coast marine), Newark-Kearney, NJ (industrial), State College, PA (rural), Point Reyes, CA (West-coast marine), and Fort Sherman, Panama (tropical marine). Among the forty-one materials exposed were four coated steel sheet products: G60 galvanized, G90 galvanized, 55% aluminum-zinc-coated, and Type 2 aluminum-coated. Results are presented for the performance of the coated sheet steels after 21 years. These results indicate the following qualitative order of corrosivity for five sites: Panama ~ Kure Beach > Newark-Kearny > State College > Point Reyes Based on changes in the corrosion of 55% aluminum-zinc-coated, an increase in the aggressiveness at Panama took place sometime during the 10th to 21st year of exposure. Future testing at these sites could be better quantified by short-term (1-2 years) exposures of standard materials. A loss of significant data from 2-, 5- and 10-year removals and initial weights for many of the test materials highlights the importance of safeguards to ensure the integrity of future long-term ASTM tests.   In terms of relative performance, the results are consistent with the following order of corrosion resistance (most-to-least). T2 100 ~ AZ55 > G90 > G60

OUTDOOR ATMOSPHERIC CORROSION STUDIES __________________________________________________________ REFERENCE: Townsend, H. E.,  ASTM STP 1421, Outdoor Atmospheric Corrosion, American Society for Testing and Materials, West Conshocken, PA 2002 This book is a collection of papers presented at the ASTM Symposium on Outdoor and Indoor Atmospheric Corrosion that was held in Phoenix, AZ in May 2001. It is the most recent in a series on a topic of continuing economic and ecological significance. As previously discussed (see “Extending the Limits of Growth through Development of Corrosion-Resistant Steel Products,” Corrosion, Vol. 55, No. 6, 1999, 547-553) controlling losses of the world’s resources due to atmospheric corrosion may be an important component of continuing economic development. Four major themes are evident in this collection. Prediction of Outdoor Corrosion Performance -- One theme focuses on prediction of atmospheric corrosion performance from climatic data, particularly in relation to methods being developed by the International Standards Organization (ISO). These attempt to classify the corrosivity of a location based either on short-term exposure of standard coupons, or on local time of wetness, and deposition rates of chloride and sulfate. Many of the assumptions in developing the ISO methodology are now being reconsidered in the light of recently completed testing, and work continues to improve the models. Laboratory and Specialized Outdoor Test Methods -- A second theme considers laboratory tests related to outdoor corrosion, and specialized outdoor methods. These include methods of evaluating the results of outdoor tests, such as, "Analyses of the Sources of Variation in Measurements of Paint Creep" by McDevitt (Bethlehem Steel Corporation), and ways to predict outdoor performance based on laboratory tests, such as those employed by Yamashita (Himeji Institute of Technology) to support development of Sumitomo's Weather Act coating, and by Yoo (POSCO) on work to develop a seaside (salt-resistant) steel by additions of calcium and sulfur. Effects of Corrosion Products on the Environment -- A third theme examines the ecological effects of corrosion product runoff, a subject that blends corrosion science, environmental technology, analytical chemistry and politics. Contributions from the Swedish Royal Institute of Technology, and the US Department of Energy reflect a growing concern in developed countries for the ecological effects of dissolved metals. Long-Term Outdoor Corrosion Performance of Engineering Materials -- The fourth theme is the documentation of the actual long-term outdoor behavior of engineering materials. This topic includes reports of the 21-year results of the 1976 ASTM outdoor atmospheric corrosion test program on nickel alloys, Galvalume, galvanized, and aluminum-coated steel sheet. Articles on the performance of unpainted, low-alloy weathering steel include a survey of utility poles in a wide range of environments, work to establish a lean-alloy (Cu-P) grade as an inexpensive alternative to A588A, and the development of a new ASTM G101 corrosion index for estimating relative corrosion resistance from composition.

EXTENDING THE LIMITS OF GROWTH THROUGH DEVELOPMENT OF CORROSION-RESISTANT STEEL PRODUCTS _____________________________________________________ REFERENCE: Townsend, H. E. , “Extending the Limits of Growth through Development of Corrosion-Resistant Steel Products,” Corrosion, 55(6), pp. 547-553 (1999). Abstract: The costs of corrosion are estimated to be about 4.2% of GDP, or about $330 billion in 1997 for the US. However, when the potential effects on extending resource productivity are taken into account, the benefits of corrosion control are substantially greater. Reports to the Club of Rome suggest that more efficient utilization of resources is essential to avoiding serious economic collapse in the next century. In preventing corrosion losses, corrosion specialists can extend the Earth’s materials and energy resources, reduce pollution, and improve the quality of life for future generations. Three examples of achieving significant increases in resource productivity through the development and implementation of corrosion-resistant steel products are given: (1) galvanized sheet for automobiles, (2) weathering steel for bridges, and (3) Galvalume sheet for metal buildings.

ATMOSPHERIC CORROSION PERFORMANCE OF QUENCHED-AND-TEMPERED WEATHERING STEEL _________________________________________________________ REFERENCE: Townsend, H. E., "Atmospheric Corrosion Performance of Quenched-and-Tempered Weathering Steel," Corroosion, Vol.56, No.2 pp.883-886 (2000). Abstract: Eight-year atmospheric corrosion tests of A 588B weathering steel were conducted in industrial, marine, and rural environments. The material was tested following two types of heat treatment: (1) quenched-and-tempered to produce a tempered martensite microstructure, and (2) normalized to produce a microstructure comprised of ferrite and pearlite. The results of these tests indicate that these heat treatments have no effect on the corrosion resistance, and that the performance of weathering steels can be estimated solely on the basis of composition. PERFORATION CORROSION OF AUTOMOTIVE STEEL SHEET ________________________________________________ REFERENCE: D. Davidson, L. Thompson, F. Lutze, B. Tiburcio, K. Smith, C. Meade, T. Mackie, D. McCune, H. Townsend, and R. Tuszynski, Perforation Corrosion Performance of Autobody Steel Sheet in On-Vehicle and Accelerated Tests, in Advances in Coatings and Corrosion Prevention, SP-1770, Society of Automotive Engineers, Warrendale, PA, 2003. Abstract: The Auto/Steel Partnership Corrosion Project Team has completed a perforation corrosion test program consisting of on-vehicle field exposures and various accelerated tests. Steel sheet products with eight combinations of metallic and organic coatings were tested, utilizing a simple crevice coupon design. On-vehicle exposures were conducted in St. John’s and Detroit for up to seven years to establish a real-world performance standard. Identical test specimens were exposed to the various accelerated tests, and the results were compared to the real-world standard. This report documents the results of these tests, and compares the accelerated test results (including SAE J2334, GM9540P, Ford APGE, CCT-I, ASTM B117, South Florida Modified Volvo, and Kure Beach (25-meter) exposures) to the on-vehicle tests. The results are compared in terms of five criteria: extent of corrosion, rank order of material performance, degree of correlation, acceleration factor, and control of test environment. Three of the laboratory accelerated tests, namely, SAE J2334, GM9540P, and Ford APGE gave results that are reasonably consistent with on-vehicle behavior.