Electrochemical Behavior of Potassium Zinc Phosphates Extract and Coating

Abstract

The electrochemical corrosion inhibitions of potassium zinc phosphate were studied by polarization, open circuit potential measurements, electrochemical impedance of the pigment extract and coating immersion test. Dynamic analysis shows that in pH=7 3.5% NaCl extract, KZn 2 (PO 4 )(HPO 4 ) functions as a cathodic inhibitor on steel and its efficiency is even superior to other phosphates. The inhibiting efficiency of the pigments on steel decrease in the order: KZn 2 (PO 4 )(HPO 4 ) > aluminum zinc phosphate > zinc phosphate ≧ aluminum triphosphate The coating tests show that potassium zinc phosphate can efficiently enhance the inhibition properties of coating and prevent the erosion of the corrosive medium by improving the barrier and hydrophobicity of the coating. The anticorrosive property of the pigments decrease in the order: KZn 2 (PO 4 )(HPO 4 )> aluminum zinc phosphate > zinc phosphate ≈APW-1.