Corrosion behavior of WC–Co coating by plasma transferred arc on EH40 steel in low-temperature

To investigate the corrosion behavior of WC–Co composite coating, plasma transferred arc (PTA) welding was applied to prepare WC–Co coating on hull steel EH40 for achieving good metallurgical bonding. The phases of coatings were mainly composed of WC particles, solid solution γ-Co, Fe3Ni2, SiO2 and Mo2C. After electrochemical test, it can be concluded that Co-based coating with 45% WC content has better corrosion resistance in low temperature marine environment for obtaining denser oxide film. Through X-ray photo electron spectroscopy (XPS) analysis, the main corrosion products of immersion were Co(OH)2 and Co3O4. These corrosion products aggregate to form a stable corrosion product film, which plays some protective role for the coating. Hard particle WC is also partially oxidized to WO3. The pitting hole of 60% WC is the most serious. Pitting corrosion is easy to occur at the interface defects.