ASTM G28 – Standard Test Methods for Detecting Susceptibility to Intergranular Corrosion in Wrought, Nickel-Rich, Chromium-Bearing Alloys
These test methods cover two tests as follows:
- Method A, Ferric Sulfate-Sulfuric Acid Test – This test method describes the procedure for conducting the boiling ferric sulfate – 50 % sulfuric acid test which measures the susceptibility of certain nickel-rich, chromium-bearing alloys to intergranular corrosion, which may be encountered in certain service environments. The uniform corrosion rate obtained by this test method, which is a function of minor variations in alloy composition, may easily mask the intergranular corrosion components of the overall corrosion rate on alloys N10276, N06022, N06059, and N06455.
- Method B, Mixed Acid-Oxidizing Salt Test – This test method describes the procedure for conducting a boiling 23 % sulfuric + 1.2 % hydrochloric + 1 % ferric chloride + 1 % cupric chloride test which measures the susceptibility of certain nickel-rich, chromium-bearing alloys to display a step function increase in corrosion rate when there are high levels of grain boundary precipitation.
The purpose of these two test methods is to detect susceptibility to intergranular corrosion as influenced by variations in processing or composition, or both.
Materials shown to be susceptible may or may not be intergranularly corroded in other environments. This must be established independently by specific tests or by service experience.
susceptibility to intergranular corrosion; nickel-rich chromium-bearing alloy