Tribocorrosion properties of nickel aluminum bronze coating prepared by cold spraying in different pH environment

Nickel aluminum bronze is the main material used to cast large ship propellers. However, marine biofouling on the surface of the propeller alters the pH value, thereby accelerating tribocorrosion and threatening ship safety. In this study, a compact nickel aluminum bronze coating with a thickness of approximately 300 μm was deposited by cold spraying. The microstructure of the coating was observed by scanning electron microscopy and optical microscopy. The electrochemical corrosion properties and tribocorrosion behavior of the coating was determined using 3.5% NaCl solution in different pH environments of 3, 7, and 11. Results show that in a pH 3 environment, optional corrosion occurs on the nickel aluminum bronze substrate, cracks mainly containing Cu are mostly distributed on α phases, deep cannelure is observed on the wear trace of the coating, and abrasive wear occurs on the coating. In a pH 7 environment, adhesive wear occurs on the substrate, slice abrasive dust is distributed on the surface of wear trace of the substrate (because porosities on the coating absorb most of the abrasive dust and avoid three body friction), cannelure on the coating is relative shallow. In pH 11 environment, surface fatigue occurs on the surface of the substrate and deep cannelure is observed on the wear trace of coating, which contains cracks. Generally speaking, tribocorrosion resistance of coating enhances during cold spray process in different pH environments, resulting from cold working hardening and abrasive dust entering the coating pores.