Electrochemical and microstructural study of time effect on the room temperature zinc phosphate conversion coating

The aim of this study is to investigate the time effect on the anti-corrosion and microstructure of zinc phosphate coatings on plain steel. St-12 plates were treated in zinc phosphate bath at different times. Potentiostatic polarization test was carried out to find out electrochemical properties of the phosphate samples in 3.5% NaCl solution. In addition, the microstructure and morphology of conversion coatings were evaluated by energy dispersive x-ray (EDS) spectroscopy and scanning electron microscope (SEM). Results showed that corrosion resistance of 30 minute phosphated sample is higher than other times and more compact and intact coating is formed at this case.