Improvement of corrosion resistance of unbalanced magnetron deposited Nb coatings by high energy metal ion pretreatment: First Prize

Abstract

The quality of corrosion resistant thin films depends on a number of factors, in particular the microstructure and degree of porosity of the coating. The micro structure of thin films deposited by the physical vapour deposition technique of unbalanced magnetron sputtering is strongly influenced by the deposition temperature and by the melting point of the condensed material. It becomes increasingly difficult to produce dense coatings at low deposition temperatures for metals such as Nb with a melting point T_M = 2500°C. The present study investigates the influence of ion etching pretreatment and of deposition temperature on the corrosion resistance of Nb thin films deposited by the combined cathodic arc–magnetron sputter deposition technique. Metal ion etching using Cr ions and Nb ions is compared to inert Ar ion etching. The coatings, deposited on 304 stainless steel substrates, are tested by potentiodynamic and potentiostatic polarisation measurements in a 3%NaCl solution and compared to electroplated chromium and electroless nickel films.