Investigating the Effect of Chemical Treatments on Corrosion Behavior of Carbon Steel via Electrochemical Noise and Polarization Methods

The effect of phosphating the surface of carbon steel and phosphating with posttreatment of passivation via chrome-free solution based on zirconium on corrosion rate and resistance of carbon-steel in 3.5% NaCl solution has been investigated via Electrochemical Noise Method (ENM) and Polarization tests (DC tests) as well. The noise resistance curves illustrate phosphating improves the resistance of carbonsteel against corrosion, and this effect enhances by post-treatment of passivation on account of the fact that a passive thin layer of zirconium dioxide forms on the surface, which can seal the porosities of phosphate coating. The result of polarization tests show that LPR of carbon-steel increases by phosphating, and thanks to the formed passive film, the LPR of carbon-steel enhances more significantly after passivation. Moreover, the role of passivating post-treatment on corrosion rate reduction is approved by results of polarization tests. Also the the result of noise resistance curves is confirmed by LPR curves.

Keywords:

Corrosion , Noise , Electrochemical