Study on an elaborated method to improve corrosion resistance of zinc phosphate coating

Coating with a dense and fine grain structure containing fewer defects, due to limiting pathways between the environment and base metal, shows more improved protection properties. The major aim of present research was to exposure of an innovative method called rephosphating, which obviously influences the formation of very fine crystalline zinc phosphate coating on the plain carbon steel. The SEM observations showed the creation of a very fine crystalline coating,using the purposed method. Furthermore, the protection properties of phosphated and rephosph ated samples were described and compared through the Neutral Salt Spray (NSS) test and the electrochemical measuring techniques such as polarization and Electrochemical Impedance Spectroscopy (EIS). The results showed that rephosphating method has beneficial influence onimproving corrosion resistance of coating in compared with it applied by phosphating method. As well, improved paint adhesion of rephosphated sample was observed in compare with phosphated sample. The outstanding point of present investigation was to refer and highlight the significant effect of surface texture circumstance in obtaining coating with improved protective properties, while in the other research activities the similar purpose have been achieved mostly through optimizing bath chemical composition

Keywords:

plain carbon steel , zinc phosphate coating , rephosphating , fine grain size structure , corrosion resistance , paint adhesion