Effects of KOH:ZnCl2 mole ratio on the phase formation, morphological and inhibitive properties of potassium zinc phosphate (PZP) pigments

Different types of potassium zinc phosphate (PZP) pigments were synthesized by a co-precipitation method. The PZPs were obtained through changing KOH:ZnCl2 mole ratio. The chemical composition of the pigments was studied by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). Then, the extracts of the PZPs were prepared in 3.5% (w/w) NaCl solution. The inhibitive performance of the pigments was investigated by polarization technique and SEM surface analysis through dipping mild steel panels in the pigment extracts for different immersion times. Results showed that changing ZnCl2/KOH mole ratio could influence formation of KZn2H(PO4)2 and KZnPO4 phases. It was known that the KZn2H(PO4)2 phase has a superior corrosion inhibition behavior in 3.5% NaCl solution than KZnPO4 phase.