材料期刊网

A novel Ti/Zr based chemical conversion coating was developed for improving the corrosion resistance of electrogalvanized steel using fluotitanate acid, fluozirconate acid and hydrofluoric acid, etc. The surface morphology was investigated by SEM. Coating composition was analyzed using XPS and FTIR. EIS and potentiodynamic polarization curves were used to evaluate the corrosion behavior. The results showed that the conversion coating was compact with the thickness of about 500 nm, and had a uniform amorphous composition that consisted of nanoscale complicated oxides or hydroxides and zinc fluorides. The Ti/Zr based conversion coating exhibited a relatively better protection for the electrogalvanized steel because the corrosion current (I(corr)) was about two orders of magnitude lower than the zinc coating substrate. EIS results indicated that the corrosion reaction of the prepared conversion coating was mixed-controlled by charge transition and diffusion charge during its three corrosion stages.