The Relationship of Heat Treatment to the Corrosion Resistance of Stainless Alloys Available to Purchase

Information is presented on the response to sensitizing heat treatments of Incoloy 800, Incoloy 825, Carpenter 20 Cb-3, Inconel 600, Inconel 625, and Hastelloy G. None of the alloys investigated was found to be consistently immune to the development of susceptibility to intergranular corrosion as measured by nitric acid and ferric sulfate-sulfuric acid evaluation tests. In most cases the two test methods were in substantial agreement but the ferric sulfate-sulfuric acid test was less sensitive to thermal effects for Incoloy 825 and more sensitive for Hastelloy G. In general, variability in resistance to sensitization as a function of prior processing history appears to be more pronounced in the higher nickel alloys than in the 300 series stainless steels.