MICROSTRUCTURE OF NOVEL CORROSION-RESISTANT COATINGS FOR STEEL-COMPONENTS BY UNBALANCED MAGNETRON SPUTTERING

Unbalanced magnetron sputtering has been used for some years to deposi t adherent, fully dense films of both pure metals and alloys. This pro cess has been utilized to deposit various aluminium alloy and zinc-nic kel coatings on steel components for corrosion protection. The process shows great promise in the automotive industry, and particularly in t he aerospace industry, as a cadmium replacement. Advantages of the pro cess include corrosion properties superior to those of cadmium, excell ent adhesion, zero embrittlement of substrate materials, zero toxicity , and good reproducibility. This paper discusses the possible variatio ns in coating microstructure due to deposition parameter alterations f or several alloy systems. Variations in alloy composition affect the c orrosion rates of the films used for cathodic protection of steel comp onents. A definite single alloy composition, for the Al-Mg system, was noted with respect to the longest time to failure in salt fog tests. (C) 1997 Elsevier Science S.A.