Effect of Cold Work on the Corrosion Resistance of Nonsensitized Austenitic Stainless Steels in Nitric Acid

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Abstract
Three austenitic stainless steels (AISI 304, 304L, and 316) were solution-annealed at 1350 K (1975 F) and water-quenched. Specimens were subsequently cold-upset forged to various degrees of cold reduction, with tensile and corrosion test specimens machined out. Corrosion specimens were exposed to boiling 65% nitric acid (ASTM Test A262 Practice C), and evaluated for corrosion as a function of cold work. Results indicate an exponential drop in corrosion rate for increasing cold work as compared to undeformed solution-annealed and quenched samples. Beyond 50% cold work for both 304 and 304L, corrosion rates began to increase perceptibly, whereas 316 registered no additional benefits of cold work beyond 10%, and no increases beyond 50%. It is proposed that the shearing of depleted zones disrupts their continuity. Intergranular attack is impeded by the creation of deformation ledges resulting from cold work. The formation of bcc martensite in 304 and 304L is thought to account for corrosion rate increases beyond the 50% cold work minimum.

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