Corrosion Behavior of Thermally Sprayed WC-Co-VC Coatings in NaCl Aqueous Solution

WC-17Co coatings are used to protect components against wear, high temperature and corrosion. WC based cermet coatings have been considered as alternative replacements to traditional hard chrome plating for improve surface properties of aircraft landing gear. This coatings are used in engineering applications requiring superior hardness and improved wear resistance, little is known about the corrosion resistance. In this study, four WC-17Co based composite coatings were deposited onto austenitic stainless steel substrates using high velocity oxygen fuel (HVOF) spraying at different concentrations of VC. The corrosion behavior was performed by linear polarization resistance test, potentiodynamic polarization curves and electrochemical impedance spectroscopy in saline environment. Characterization of the coating structure, morphology and composition, was carried out, prior to and after corrosion testing, using scanning electron microscopy and EDX elemental analysis. It was determined that the anodic branches present a tendency to passivation this more pronounced in sodium chloride. The results showed the addition of nanostructured WC-17Co particles improved corrosion resistance in H2O and NaCl. The addition of VC did not affect the corrosion behavior of the bimodal thermal spray coating. The electrochemical data showed that sample with 50 % of nanoparticles of WC-17Co presented higher corrosion resistance than the others in chloride solutions.