Electrolytic deposits on stainless steel as high temperature coatings

Conversion coatings modified by deposits of alumina, with or without zircon ium, calcium, or strontium additions, have been studied as a way of improvi ng the thermal oxidation resistance of a 17 Cr ferritic stainless steel. Co nversion coatings, characterised by a particular morphology and strong inte rfacial adhesion with the substrate, facilitate the electrochemical deposit ion of ceramic layers and enhance their adhesion to the substrate. After he ating, the coatings present a continuous composition gradient with refracto ry compounds at the surface. The influence of added elements (Zr, Ca, or Sr ) on the behaviour of the alumina coating was investigated at 1000 degreesC . Calcium improved the protective character of the alumina coating. The mor phology and chemical composition of the different deposits were also analys ed and results on the thermal stability of such coatings on Fe-17 Cr ferrit ic stainless steel are presented.