Improved microstructure and physiochemical properties of hopeite conversion coating by Si3N4 nanoparticles doping

Abstract

The effect of nano-scaled Si3N4 particles on the microstructure, mechanical and electrochemical behavior of hopeite (Zn3(PO4)2·4H2O) conversion coating on pure titanium was investigated. Different concentrations of nanoparticles were dispersed into the phosphating bath to incorporate the process of coating deposition. The XRD results demonstrated that nano-Si3N4 were doped into the coatings without any decomposition or reaction with the hopeite phase. A finer and denser microstructure of the composite coating could be obtained at the addition of 0.5 g/L Si3N4 in comparison with the pure hopeite coating. Moreover, the composite coating presented a higher bonding strength and corrosion resistance related to the refinement of microstructure and filling of the embedded nanoparticles. It is suggested that the incorporation of nano-Si3N4 particles in conversion coating is a promising approach for performance optimization.

Keywords

• Nanoparticles
• Conversion coating
• Hopeite
• Bonding strength
• Corrosion resistance