Comparative study on corrosion behavior of WC-MgO composite and WC-6Co cemented carbide in NaCl solution

Abstract A comparative study on the corrosion behavior of novel WC-MgO composite and WC-6Co cemented carbide was carried out in 3.5 wt% NaCl solution with immersion and electrochemistry method. The result indicates that WC-MgO composite possesses higher corrosion resistance than WC-6Co cemented carbide. The key reason for higher corrosion resistance of WC-MgO composite is the dense and flat WO3 passive film which can protect inner material to avoid further corrosion successfully. The main corrosion mechanism for WC-MgO composite is typical pitting and oxidation of WC phase. The reaction of MgO and Cl− promotes the dissolution of MgO phase, which is the main reason of pitting formation. For WC-6Co cemented carbide, the corrosion products are porous, which cannot protect inner material to avoid further corrosion. The difference of corrosion mechanism can be attributed to the replacing of Co binder with MgO, which avoids the formation of galvanic corrosion between WC and Co.