Corrosion of Alloys at High Temperatures Under Calcium-containing Deposits

Airborne hot section turbine components are exposed to ingested atmospheric pollutants, sand, marine salts, and/or fuel impurities, resulting in calcium-containing deposits. One resulting consequence is deposit-induced corrosion, which can lead to solute depletion in the alloy and removal or destruction of the external protective oxide scale. This presentation focuses on our current work on two compounds of interest in deposits - calcium oxide and calcium sulfate as well as combinations of these compounds with sodium chloride and sea salt. These deposits were applied to the surface of model binary Ni-Cr alloys and Ni-base superalloys exposed to high temperatures under different atmospheres for different times. Post-test characterization enabled insights into degradation mechanisms.