Alginate was used as easily and cost effective polymer to synthesize zinc oxide nanoparticles in an aqueous solution at ambient temperature (ZnOAlg-NPs). FTIR, and XRD were used to characterize the prepared zinc oxide-Alginate nanoparticles. Zeta potential value of ZnOAg-NPs was determined and found to be 7.09 mV indicating higher stability of the prepared nanoparticles. The capacity of a novel epoxy coating (Epoxy/ZnOAlg-NPs coating) on covered carbon steel in 3.5 wt% NaCl liquid was examined. The addition of ZnOAlg-NPs boosted anti-corrosion and epoxy coating performance. In the Epoxy/ZnOAlg-coated steel case, only one semicircle is visible, with coating resistance 1612 kohm cm2 and coating capacitance 9.8 × 10−9 F cm−2.