Abstract: A protective coating for aluminum alloys, electrode for producing same and a coating process using the welding electrode. The protective coating and electrode comprise a composite consisting essentially of alumina particles in a matrix, wherein the matrix is a metal selected from the group consisting of aluminum or an aluminum alloy. The alumina particles consist of aluminum oxide in powder form. The coating process using the welding electrode above comprises the steps of: electro-spark depositing a composite on to a substrate, wherein the composite consists essentially of alumina particles in a matrix, wherein the matrix is a metal selected from the group consisting of aluminum or an aluminum alloy. The substrate herein is an aluminum alloy. The coatings involve only aluminum and aluminum compounds, thereby intermetallic compound formation and galvanic corrosion of the coating-substrate materials system is avoided.