Synergetic effect of thickness and oxygen addition on the electrochemical behaviour of tantalum oxide coatings deposited by HiPIMS in DOMS mode

The HiPIMS technique in DOMS mode was used to deposit tantalum (Ta) and Ta1-xOx films. After depositing pure metallic Ta and Ta1-xOx films with two different thicknesses, their structure, morphology and chemical composition were investigated. Nano-indentation was used to evaluate the hardness of the films. OCP, potentiodynamic and EIS in artificial saliva at T = 37 degrees C were used to investigate the corrosion behaviour of the coatings. The results showed that, in the case of metallic coatings, increasing the film thickness, the beta-phase becomes dominant over the alpha-phase, which compromised both the mechanical and electrochemical behaviours. Tantalum oxide films raised the polarisation resistance of the non-reactive coatings (metallic ones), exhibiting values 2-3 orders of magnitude higher.