Comparison of the Corrosion Behavior of Conventional and Nanostructure Tungsten Carbide Coatings with Metal Substrate WC-20Cr-7Ni in Sulfuric Acid Corrosive Media

In this research, electrochemical behavior of conventional and nanostructure composite tungsten carbide coating with WC-20Cr-7Ni metal substrate prepared by HVOF thermal spray on carbon steel in 5wt% sulfuric acid corrosive media was studied. Coatings structures were determined by X-ray diffraction analysis (XRD) and their corrosion resistance was studied by electrochemical potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Corrosion products on the test specimens and in the sulfuric acid corrosive media were analyzed by Scanning electron microscopy with energy dispersive X-ray analyzer (SEMEDX) and Atomic absorption spectrometer respectively. Results showed that heat treated nanostructured WC-20Cr-7Ni has better corrosion resistance and lower corrosion current density compared with non heat treated coatings. Nickel of The non heat treated coat was solved in the corrosive media but after heat treatment there is not any Nickel in the solution. Chromium oxides as a corrosion products were stick to the surface of coatings.