Galvanic corrosion resistance of aluminum and its alloy in galvanic couples with steels with metallic coatings

Abstract

The aim of this work is comparison of corrosion resistance of aluminum and its alloy D16 to galvanic corrosion in couples with carbon steel A284 and stainless steel type 321, on the surface of which various metallic coatings were deposited. Zinc, cad mium and aluminum used as the metal coatings on the steel. Coatings deposited by electroplating and vacuum ion-beam assisted deposition. Study of galvanic coupling of deposited coatings with aluminum and its alloy carried out by electrochemical methods in a 3% NaCl solution. Zinc and cadmium coatings on steel, formed by both methods, have electrochemical characteristics of deposited metals. Zinc coatings in galvanic couples with aluminum and its alloy are anodes and aluminum coatings are cathodes. Compromise potentials of cadmium coatings approximately coincide with those for aluminum and its alloy. Current density of the galvanic corrosion of aluminum and its alloy in galvanic couples with steel with-out coatings was ~10{–2}mA/cm{2}, and in galvanic couples with aluminum coatings on steel – ~10{–3}mA/cm{2}. Corrosion current density of zinc in coatings was 2 ⋅ 10{–2}mA/cm{2}, and cadmium – 6 ⋅ 10{-3} mA/cm{2}. Best galvanic compatibility with aluminum and its alloy D16 in 3% NaCl have cadmium coatings.