Corrosion protection properties of electroless Nickel/PTFE, Phosphate/MoS2 and Bronze/PTFE coatings applied to improve the wear resistance of carbon steel

The aim of this work is the evaluation of corrosion behaviour of some industrial coatings on carbon steel, utilised to improve tribological behaviour. In particular, composite electroless nickel coatings with polytetrafluoroethylene (PTFE) particles, sintered bronze in PTFE matrix layers and zinc phosphates—with and without MoS2 coatings—were analysed. Salt spray fog exposure and electrochemical tests were carried out. Electroless nickel coatings showed the best protection properties with a good barrier protection, because of the coating structure: an external layer, which contains PTFE particles improving tribological properties, and an inner nickel layer, which protects against corrosion because of barrier effect. PTFE-coated sintered-bronze samples showed limited corrosion resistance due to the high number of defects present. The application of a MoS2 polymer-embedded layer improves the characteristics of phosphate conversion coatings, which, by themselves, cannot assure good protection.