An Improved Intergranular Corrosion Test for HASTELLOY® Alloy C-276

Abstract

Presently, the most widely used susceptibility test for intergranular corrosion of HASTELLOY® Alloy C-276 is the ferric sulfate-sulfuric acid test. The corrosion rate obtained by this test has uniform and intergranular corrosion components. The uniform corrosion rate, which is a function of minor variations in alloy chemistry, may easily mask the intergranular corrosion component of the overall corrosion rate. A new solution chemistry identified through laboratory tests resolves the problem and displays a step function response in corrosion rate when there are high levels of grain boundary precipitation. Over 700 production specimens have been comparatively tested in both solutions, spanning a time period of two years. The new test consistently detects undesirable microstructural conditions in HASTELLOY Alloy C-276 that, in many cases, are not detected by the ferric sulfate-sulfuric acid test.