Fig. 2 shows changes in weight of AL and bare 304 stainless steel during oxidizing at 1100°C. The oxidation resistance after aluminizing was markedly improved in comparison to that of bare 304 stainless steel. When an alloy containing Cr and Al is exposed to a high-temperature oxidation environment, Al2O3 and Cr2O3 scales are formed on the surface of the alloy.These scales prevent the rapid oxidation of iron in the
alloy, thereby eliminating the dissolution and inward
diffusion of oxygen. At temperatures higher than
1000°C, the Cr2O3 scale, however, does not prevent the
rapid oxidation of iron in the alloy due to the volatilization.
As shown in Fig. 2, the improvement in oxidation
resistance of the aluminized 304 stainless steel is, therefore,
due to a protective Al2O3 scale formed on the
coating surface, while a volatile Cr2O3 is only formed
on the 304 stainless steel surface without coating.