Conversion coatings on stainless steel were used asa support for alumina coatings deposited by electrolytic treatment from an aqueous solution of aluminium sulphate. The conductive conversion coating with its particular morphology facilitates the reduction reactions responsible for the increase of the pH at the surface and acts as a porous electrode allowing favourable local pH conditions for aluminium oxyhydroxide deposition. The effects of potential, current density, time, temperature and stirring on coating weight were studied.