COMBINED STEERED ARC-UNBALANCED MAGNETRON GROWN NIOBIUM COATINGS FOR DECORATIVE AND CORROSION-RESISTANCE APPLICATIONS

Unbalanced magnetron deposited niobium coatings show a dense structure approaching that of the bulk material and an optimum corrosion perfor mance on razor blade steel when grown with negative bias voltages betw een -75 and -100 V, a bias current of approximately 1 mA cm(-2) and a substrate temperature of 400 degrees C. The pre-treatment with either niobium or argon ions influences the growth mechanism considerably, in particular the grain size and crystallographic orientation. Anodic ox idation in dilute weak aqueous acids leads to oxide interference colou rs allowing the generation of deep blue, steel blue, lime green, red, yellow and golden colours.