Corrosion protection of mild steel by an alkyd resin coating reinforced with calcium zinc phosphate derived phosphate sludge as green inhibitive pigment

An anti-corrosion pigment of calcium zinc phosphate (CaZnPps) was developed basing on a by-product of phosphate mining industry, using dissolution-precipitation method, and incorporated into alkyd resin coatings applied on carbon steel. The elaborated pigment was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The anticorrosion effectiveness of CaZnPps was examined on carbon steel submerged in a 3% NaCl solution, by electrochemical impedance spectroscopy (EIS) and linear polarization curves. Findings highlighted substantial inhibitory efficiency, achieving an 85%. The protective performance of modified and reference alkyd resin coatings applied on carbon steel was studied by EIS technic. The modified coatings showed significantly improved long-term corrosion protection compared to reference coatings. The effect was attributed to the synergistic combination of the corrosion inhibition effect of zinc phosphate calcium pigment and alkyd resin healing capability.