Influence of Iron Chloride Containing Test Environments on Stress Assisted Corrosion Phenomenon

The addition of a controlled quantity of iron chloride (FeCl2) to a test solution allows for tight control of the pH in Sulfide Stress Cracking (SSC) tests for low alloy steels. The natural buffering capacity results from the early-stage precipitation of iron sulfide corrosion products during the corrosion test. Previous works have established a reduction in the corrosion rate in such environments, while the susceptibility to SSC remains high, even higher than in standardized solutions with significant pH drift during the test. This led to the conclusion that iron chloride solutions allow a fair assessment of the SSC susceptibility of a material because both applied stress and key environmental parameters (pH and PH2S) remain constant throughout the test duration. This work provides evidence that Stress Assisted Corrosion (SAC) phenomena on the surface of NACE TM0316 four-point bend specimens sampled in linepipe grades are suppressed in such test environments. Results are interpreted in light of current knowledges on the mechanism of groove formation, and the interest in using iron chloride solutions for the qualification of the SSC resistance of linepipe grades is discussed.