Low-Temperature Hot Corrosion in Gas Turbines: A Review of Causes and Coatings Therefor

In about 1975 an apparently new form of hot corrosion attack of gas turbine airfoils was identified during low-power, low-metal-temperature operation of a marine gas turbine. The rate of this corrosion was substantially greater at about 700° C than that usually observed for sulfate-induced hot corrosion at 800° to 1000° C. The same type of hot corrosion has been subsequently reported to occur in ground-based gas turbines, and is similar in principle to fireside corrosion of boiler tubes. This paper presents a review of probable mechanisms of this so-called low-temperature hot corrosion, of test methods for its laboratory and rig simulation, and of coatings in use or in advanced development for protection of gas turbine airfoils operating in this corrosion regime.