Investigation the effect of passivation on corrosion behavior of carbon steel via Electrochemical Noise and Polarization methods

The effect of passivation the surface of carbon-steel via chrome-free solution based on zirconium and by chromate soltion 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). The noise resistance curves illiustrate noise resistance of samples in 3.5% NaCl solution enhances after passivation via zirconium solution, as well as chromate solution, on account of the fact that a passive thin layer of zirconium dioxide forms on the surface of carbon-steel samples. Thus, noise resistance of samples enhances; in other words, resistance of carbon-steel against corrosion increases by passivation.
The results of polarization tests show that LPR (Linear Polarization Resistance ) of carbon steel increases by passivation via zirconium based solution as well as chromate solution does. The results of polarization tests also illustrate that corrosion rate is reduced by passivation via zirconium solution and chromate solution. Also the results of noise resistance curves are confirmed by LPR curves. To sum up, zirconium solution can be an appropriate alternative to replace chromate solution as passivation solution since chromate solutions are toxic.