Evaluation of Additives for Prevention of High Temperature Corrosion of Superalloys in Gas Turbines

A number of commercially available chemical additives for utilization in modern high temperature gas turbines were evaluated for their corrosion and deposit inhibiting characteristics. The evaluation was made in pressurized passages which simulate conditions of operating gas turbines. Initial screening tests of 10 hr each were made with a contaminant level of 50 ppm vanadium, and promising additives were further tested for times up to 300 hr at the more realistic contaminant level of a No. 3 GT fuel. Characteristics of the deposits were studied with x-ray diffraction and ash fusion tests. Corrosion rates for various alloys tested with treated fuel were measured and compared to test results obtained with untreated fuel. Conclusions were drawn as to the type of elements most effective in reducing corrosion caused by combinations of vanadium and sodium. The role of elements in preventing deposit buildup is also assessed.