Sodium vanadate induced corrosion of MCrAlY coatings – Burner rig studies

Abstract

Abstract The corrosion of several MCrAlY‐coatings (M = Ni, Fe and Ni + Co) has been studied in a high velocity burner rig at 650, 800 and 950°C. The fuel used was diesel oil with additions of 3% sulphur, 200 ppm vanadium and 100 ppm sodium. The deposits formed on the specimens mainly consisted of sodium vanadates which were molten at the test temperature. Sodium sulphate was only found at and below 650°C. The corrosion mechanism involved was vanadate‐induced hot corrosion. This corrosion mechanism is characterized by the formation of an oxide layer adjacent to the metal, the dissolution of oxide in the molten deposit, and precipitation of vanadates or oxides near the outer surface of the deposit. The continuous deposition of fresh vanadate on the surface served to maintain high corrosion rates for extended exposures.