Materials Performance

NOV 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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19 MATERIALS PERFORMANCE: VOL. 57, NO. 11 NOVEMBER 2018 Information on corrosion control and prevention Stainless Steel Creates an Art Deco Masterpiece W ith the Delhi Pillar (Delhi, India), improved corrosion resistance was achieved through alloy additions to the iron, but this was the result of luck with the ore used. It was not until the late Victorian era that scientif ic investiga- tions produced the precursors to the modern corrosion-resistant steels in use today. The discovery in 1882 of Hadf ield 's manganese steel with its remarkable wear-resisting properties probably started serious investigations into means of making major improvements in steel properties by controlled additions of alloys. However, attempts at improving the corrosion resistance of steel had commenced early in the 19th century. Michael Faraday carried out experiments alloying iron with noble metals such as platinum, although the results were disappointing. Harry Brearley in Sheff ield, United K ingdom is often considered to be the inventor of stainless steel (SS), but in fact there were important discoveries made before he prepared the f irst martensitic stainless in 1913. In 1911, Monnartz and Borchers in Germany discovered three important facts regarding SS. First, the correlation between chromium content and corrosion resistance; second, that a signif icant boost in corrosion resistance is achieved when the chromium content exceeds 10.5%; and f inally, that molyb - denum can have an important inf luence on corrosion resistance. Monnartz is also the f irst to use the term "passivity" to describe the improvement in corrosion resistance. Concurrently, Eduard Maurer and Benno Strauss at the Krupp works in Germany alloyed steel with both chro- mium and nickel to produce the f irst aus- tenitic SS. However, it was Brearley who recognized the commercial signif icance of SS and developed the large-scale pro- duction of the metal, initially for cutlery. In the early 1920s, a whole variety of chro- mium and nickel combinations were tried, with the best known being the 18/8 or 304 SS (18% chromium, 8% nickel). The addition of nickel produced a SS that was more ductile, and more resistant to acid. Iron pillar at New Delhi, India. William Van Alen's Chrysler Building in New York City with its SS cladding is considered to be an architectural marvel. Most of the standard grades produced in these early years are still in use today. The f irst major use of SS in architec- ture, an example that arguably has not been surpassed, is the Chrysler Building, erected in New York City (New York, USA) in 1930. Walter Chrysler engaged archi- tect William Van A len to design the tall- est building in the world, and at the same time produce a building that would pro- mote his automobiles. A Krupp version of 18/8 stainless known as "Nirosta" was selected as the cladding metal. The gar- goyles are supposed to represent Chrysler hood ornaments. The stainless-clad radi- ating arched crown in a sunburst pattern is the most impressive feature of the Art Deco masterpiece. When the spire was added in 1930, it was the tallest building in the world, but less than a year later it was overtaken by the nearby Empire State Building. The building was declared a National Historic Landmark in 1976, and is often f irst in polls of architects, engi- neers, historians, and builders as their favorite building in New York. A committee was set up to inspect the condition of the building every five years as there was an obvious interest in the durability of SS in architectural applica- tions. This committee was disbanded in 1960 because there had been virtually no deterioration of the panels. The top of the building has been cleaned manually only twice, in 1961 and 1995. During the 1995 cleaning, some dents and cracks were observed and repaired, and superficial pitting near an incinerator vent was detected. But the condition of the stain- less was found to be excellent, looking like it had just been installed. As one commen- tator has noted, "With its stainless steel crown gleaming in the sun … the Chrysler building always looks like the future." A lloying to make steel corrosion- resistant was effective, but most applica- tions required something much cheaper. Therefore, putting a barrier between the steel and its environment, a protective coating, has become the single most important means for preventing corro- sion. And, as we shall see next month, the most effective way is to apply a thin layer of zinc to the steel. Further reading: Harold M Cobb, "e History of Stainless Steel," ASM International, (2010). Source: NACE International member Robert A. Francis, Ashburton, Victoria, Australia—email: RobFrancis766@gmail. com.

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