Fe-23 Cr-5Al stainless steel was functionalized by a conversion treatment in order to allow alumina electrodeposition with strong interfacial bonding. The very porous conversion coating prepared in acid solution had excellent adhesion and was conductive enough to permit cathodic reactions inducing local pH conditions favourable for the precipitation of alumina oxyhydroxide during electrolysis of aluminium salt solutions. The coating presented chemical composition gradients suitable for strong adhesion. The improvement of the thermal oxidation behaviour was studied at 1000 degrees C.