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Polyvinyl alcohol (PVA) was added to the phosphate solution to enhance its corrosion protection properties. The surface morphology and corrosion resistance of the coatings without and with PVA were studied by scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and polarization technique. Results showed that addition of PVA to the phosphate solution reduced the grain size of the phosphate crystals. PVA increased the population density of the coating through increasing the nucleation sites. The inhibitory role of the PVA resulted in the decrease of the steel corrosion rate through formation of ZnP-PVA and Fe-PVA complexes.

The surface morphology and composition of the cerium-based conversion coatings (Ce) were studied for the St-37 steel substrate which was post-treated in an ambient temperature zinc phosphate chemical treatment bath (Ce–Zn). Then, the epoxy/polyamide coating was applied on the substrates treated with Ce, Zn and Ce–Zn chemical treatments. The surface characterization and electrochemical investigations were made by scanning electron microscope (SEM), energy dispersive X-ray photoelectron spectroscopy (XPS), contact angle measuring device, pull-off test and electrochemical impedance spectroscopy (EIS). Results revealed that the epoxy coating applied on the Ce–Zn treated sample showed the highest adhesion and corrosion protection properties.

Steel substrates were chemically treated by room temperature zinc phosphate conversion coating. Poly(vinyl) alcohol (PVA) was added to the phosphate solution as a green corrosion inhibitor. Finally, the epoxy/polyamide coating was applied on the untreated and surface treated steel samples. The effects of PVA on the morphological properties of the phosphate coating were studied by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle measuring device. The adhesion properties of the epoxy coatings applied on the surface treated samples were investigated by pull-off and cathodic delamination tests. Also, the anticorrosion properties of the epoxy coatings were studied by electrochemical impedance spectroscopy (EIS). Results showed that addition of PVA to the phosphate coating increased the population density of the phosphate crystals and decreased the phosphate grain size. The contact angle of the steel surface treated by Zn-PVA was lower than Zn treated one. The corrosion resistance of the epoxy coating was considerably increased on the steel substrate treated by zinc phosphate conversion coating containing PVA. PVA also enhanced the adhesion properties of the epoxy coating to the steel surface and decreased the cathodic delamination significantly.

An investigation is presented into the effect of particle size distribution on the aggregation behavior of colloidal dispersions and validity of the Derjaguin-Landau-Verwey-Overbeek(DLVO) theory. The colloidal dispersions of epoxy amine adducts were prepared with various particle size distributions (PSD) and surface charge densities. Moreover, the Fuchs stability ratios W were obtained in aqueous solution with and without consideration of the viscous effects. It was found that PSD of colloidal dispersions affect the reliability of the prediction of DLVO theory. In order to achieve a good agreement between experimental and theoretical critical coagulation concentration (CCC) values of the colloidal dispersions, a new expression with consideration of particle size distribution was introduced.