Effects of Al and Si on the Anodic Polarization Characteristics of Fe-10Cr Alloys

Effects of alloying of Al and Si on anodic polarization of Fe-10Cr alloys have been studied in order to assess the possibility of obtaining a lower Cr content stainless steel. Experimental mesurements have been made on anodic polarization curves in 0.05-1.0 kmol·m−3 H2SO4 aqueous solution, pitting potentials in 3.5%NaCl aqueous solution and repassivation potentials in 0.05 kmol·m−3 H2SO4+0.05 kmol·m−3 NaCl aqueous solution.The critical current density for passivation decreased with the increase of Al and Si contents in Fe-10Cr alloys. It was evident that Si exerted a greater influence than Al. The passive current density decreased with increasing Si content. In the case of adding 1%Al, the passive current density decreased, and there was almost no change in the current density in the case of >1%Al addition to Fe-10Cr alloys. The critical current density for passivation and the passive current density increased with increasing concentration of H2SO4. An Fe-10Cr-3Al-3Si alloy showed the lowest critical current density, and an Fe-10Cr-3Si alloy showed the lowest passive current density. It was indicated that the pitting potential moved to noble direction with increasing Si content. On the other hand, it moved to noble direction with Al content until 3%, however this beneficial effect was decreased by more than 3%. In repassivation behavior, an Fe-10Cr-3Al-3Si alloy showed the most noble potential among the alloys investigated. It is suggested that Fe-10Cr alloys containing Al and Si have a corrosion resistance which is equal to or greater than that of Fe-12Cr stainless steel.