The Evolution of the Tensile Properties of MoS-Coated Titanium Alloy Bolts Under the Synergistic Damage of NaCl Corrosion and Preloading

MoS coating is a newly developed method to prevent bolt corrosion and the seizure of bolts used in equipment in sea areas. It is of great significance to investigate the evolution of the tensile properties and intact coatings for the maintenance of coated bolts. To evaluate the tensile properties of MoS-coated titanium alloy bolts, titanium alloy bolts coated with MoS (TC4+MoS) and bolts treated with a composite treatment of anodizing oxidation and MoS coating (TC4+AO+MoS) were corroded in salt spray tests for 4300 h. The MoS coating significantly enhanced the bolts' corrosion resistance, demonstrating exceptional protective performance by only experiencing minor peeling due to oxidation-induced cracking of the coating during the extensive 4300 h salt spray test. The tensile strengths of the TC4+MoS and TC4+AO+MoS bolts both decreased as compared with the original bolts. The bolts pretreated with anodic oxidation revealed lighter coating peeling and maintained a higher tensile strength after corrosion. Therefore, it can be concluded that the coatings provided excellent corrosion resistance, leading to a minor impact on the bolts' tensile strength and fracture behavior under the synergistic damage of sea water corrosion and preloading.