Relationship of Corrosion Resistance–Coating Structure of HP/HVOF Carbide and Metallic Coatings

A study was carried out on the corrosion resistance of the JP- 5000 coatings of Superalloy 625, WC-12%Co, WC-17%Co, WC-10%Co-4%Cr and Cr₃C₂-25NiCr materials and comparisons made with chrome plating. The coating corrosion resistance was evaluated using the standard salt fog test (ASTM B117) and also by submersion tests in 10% FeCl₃ solution (ASTM G48), in 10% HNO₃ and in 0.1M H₂SO₄ + 0.2M HCl solutions. The coating corrosion mechanisms in relationship with the coating microstructure and phase constitutions are discussed. The test results show that the HP/HVOF coating corrosion resistance can be significantly improved through spray parameters and coating structure optimization. All coatings tested herein having optimum microstructure and phase constitutions have shown improved corrosion resistances in comparison with chrome plating.