Influence of a silane treatment on the corrosion resistance of a WE43 magnesium alloy

The possibility that various chemical treatments may enhance the corrosion resistance of a magnesium alloy (containing rare earths, WE43 alloy) has been investigated. Cerium(III) conversion coatings and silanic coatings, with and without acid pickling, were tested in 0.1 N Na2SO4 solution. Silanic coatings were obtained by dipping WE43 specimens in diluted hydroalcoholic silanic solutions and successively cured at 100 °C for 1 h.A silanic compound with a long aliphatic chain (e.g. n-octadecyltrimethoxysilane, OctadecS) produced a very protective and relatively persistent coating, while that with a mercapto group (3-mercapto-propyl-trimethoxysilane, PropS–SH) formed less protective layers. Treatments with cerium salts (cerium(III) sulphate or cerium(III) chloride + hydrogen peroxide) did not produce encouraging results. Under no conditions did acid pickling improve the performance of the coatings.