Effects of Pt and Si on the low temperature hot corrosion of aluminide coatings exposed to Na2SO4-60 mol% V2O5 salt

Hot corrosion of pack (zero/medium) Pt-modified aluminide and slurry (zero/low/medium) Pt-modified silicon-aluminide coatings exposed to a Na2SO4-60 mol%V2O5 deposit at 700 °C was evaluated using the deposit recoat technique. Thickness loss metrology was utilized to study corrosion penetration into the coatings. The corrosion products and remaining coatings were characterized by means of SEM, EDX, XRD and EPMA. The aluminide coating and medium Pt-modified silicon-aluminide coating showed the worst and the best corrosion resistance, respectively. Enhanced hot corrosion resistance of the Pt-modified silicon-aluminide was attributed to microstructure of the coating with a two-phase PtAl2-NiAl outer layer and formation of refractory silicides.