Studying the effects of poly (vinyl) alcohol on the morphology and anti-corrosion performance of phosphate coating applied on steel surface

• Polyvinyl alcohol has been added to the phosphate solution to minimize the porosity.
• Surface characteristics and anticorrosion properties of phosphate coating were studied.
• It was found that polyvinyl alcohol could reduce the grain size of phosphate crystals.
• Polyvinyl alcohol could enhance the corrosion resistance of the phosphate coating.

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.

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