Preparation and characterization of electrolytic alumina deposit on austenitic stainless steel

Conversion coating modified by alumina has been studied as a way for improving the resistance to thermal oxidation of an austenitic stainless steel. Conversion coating, characterized by a particular morphology and strong interfacial adhesion with the substrate, facilitate the electrochemical deposition of ceramic layers and enhance their adhesion to the substrate. The influence of the current density and treatment time on alumina deposit was studied using statistical experimental designs like Doehlert uniform shell design. After heating, coatings present a continuous composition gradient with refractory compounds at the surface. The behavior at high temperature (1000°C) of the alumina coating was investigated. The presence of alumina increases the oxidation resistance of an austenitic stainless steel at 1000°C. The morphology and the chemical composition of the deposit are analyzed. Results on the thermal stability of coating on austenitic stainless steel are presented.