Effect of Heat Treatment and Bath Process Parameters on the Corrosion Behavior of Ni-P-TiO2 Composite Coatings

The present research article deals with the study of corrosion behavior of Ni-P-TiO 2 composite coating.The TiO 2 composite coating is deposited on the mild steel substrate.Corrosion behavior of the TiO 2 composite coatings after heat treatment at various annealing temperatures (300 °C, 400 °C, and 500 °C) is evaluated with the help of potentiodynamic polarization test using 3.5% NaCl solution.The electrochemical parameters, corrosion potential (E corr ) and corrosion current density (I corr ), are optimized for maximum corrosion resistance using Taguchi based grey relational analysis.The coating parameters, namely, nickel sulphate, sodium hypophosphite, concentration of TiO 2 particles and annealing temperature are considered as main design factors.The analysis of variance (ANOVA) revealed that the annealing temperature and concentration of TiO 2 particles have significant influence on the corrosion behavior of the composite coating.The microstructure characterization of the coating is conducted using scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction analysis.The Ni-P-TiO 2 composite coating exhibits nodular structure with uniform incorporation of titanium particles and converts into the crystalline structure after heat treatment.