Improving Corrosion Resistance of Coatings Created by Plasma Electrolytic Oxidation Method on Pure Titanium Substrate Through Fractional Factorial Design

Plasma electrolytic oxidation coating has emerged as a relatively new method to increase the corrosion resistance of metals. This research aims to improve the corrosion resistance of coatings applied on pure titanium substrate by optimizing the parameters of the coating process. For this purpose, the experiments were designed using the fractional factorial design method to determine the determinants of a response. The main factors of the process include electrolyte concentration, electrical parameters (current density, frequency and duty cycle) and treatment time at two different levels. The microstructural and phase analysis of the coating were carried out using Scanning Electron Microscopy and X-Ray Diffraction (XRD). Corrosion behavior of coatings in 3.5 wt% NaCl solution was studied by electrochemical impedance spectroscopy analyze. Statistical analysis showed that the optimal conditions can be obtained in the concentration of 5 g/L sodium phosphate, 4 g/L potassium hydroxide, current density 6 amps/square meter, duty cycle 80%, frequency 1000 Hz, and treatment time of 10 min.