Electrochemical comparison between corrosion resistance of some thermally sprayed coatings

Electrochemical polarisation and impedance spectroscopy tests in 0.1 M HCl and 0.1 M H2SO4 solutions were performed on HVOF-sprayed cermet coatings (WC-17% Co, WC-10% Co–4% Cr) and Atmospheric Plasma-Sprayed (APS) ceramics (Al2O3, Al2O2?13 wt%TiO2, Cr2O3) with APS bond coat (Ni-Co-Cr-Al-Y). Reference tests were also performed on hard chrome electroplating. Plasma-sprayed coatings offer limited substrate protection owing to interconnected porosity, although the bond coat promotes some forms of passivation in H2SO4 HVOF-sprayed cermets possess good corrosion resistance in both environments. Chrome electroplating shows comparatively better corrosion resistance in H2SO4, but worse in HCl.