Deposit-Assisted Corrosion of Heat-Resistant Alloys

Chloride-based deposits can significantly accelerate the progress of elevated temperature degradation of stainless steels and nickel-base alloys. Such deposits are present in the byproducts of combustion of biomass fuels and are common in the environment experienced by hot automotive exhaust components. A test was developed to investigate the susceptibility of materials to attack under chloride salt deposits at elevated temperatures, using a sample incorporating stressed, unstressed, and welded segments. Both gravimetric and metal recession measurements were used to determine the progression of corrosion. Nickel-base alloys were found to be resistant to deposit-assisted attack, while common stainless steels were prone to scaling and exfoliation. Results will also be presented on recently developed higher-alloy content stainless steels which exhibit corrosion resistance similar to that of the nickel-base superalloys.