Corrosion analysis of copper -TiO2 nanocomposite coatings on steel using sputtering

The corrosion resistant coatings used conventionally are susceptible to degradation, leading to pitting corrosion. This report summarizes the corrosion resistant nature of thin films of Cu-TiO2 coated on mild steel, in different corrosion environments. Nano meter thick (100nm, 125nm, 150nm) composite coatings were coated on steel substrate by RF magnetron sputtering technique. The required targets used in sputtering were fabricated indigenously by compacting a mixture of 20% and 25% of TiO2 nano powder with copper metal powder in a universal testing machine. The thin films of Cu-TiO2 nano composite coatings obtained by sputtering were characterized using XRD, AFM and SEM. The corrosion resistance of nano composite coatings in different media was analyzed using weight loss and electrochemical methods. Electrochemical polarization results revealed the shifting of corrosion potential of mild steel (Ecorr = 0.413V vs. Ag/AgCl) to more positive side when coated with Cu-TiO2 (-0.377V). Electrochemical impedance spectroscopy analysis results also confirmed150 nm coated steel has higher resistance values (475Ω) than uncoated steel. The results of the weight loss method also substantiate increase in corrosion resistance of copper based nano composite coatings. KEYWORDS— Corrosion resistant coating, Sputtering, Tafel plot, Nyquist diagram, Cu-TiO2