Abstract
Herein, 5-10 nm-sized rod-like nanocrystalline CeO(2) and CeO(2)-CuO nanocomposite were synthesized and incorporated into zinc phosphate coatings as corrosion inhibition additives. The formulated coatings were studied thoroughly on mild steel in 3.5% NaCl solution and compared with unmodified coating. The concentration of the additive was varied from 0.3 g L(-1) to 0.9 g L(-1) with three step-ups. X-ray and surface analysis results revealed that both additives favoured the formation of more compact coatings with densely packed zinc phosphate crystals and reduced iron content. Compared with the unmodified coating, the metal oxide incorporated coatings showed low corrosion current density (I (corr)) and corrosion rate and high polarisation resistance (R (p)) and charge transfer resistance (R (ct)), confirming that these nanomaterials act as corrosion inhibitors. Among the three concentrations used, nanocrystalline CeO(2) performed well at 0.6 g L(-1) and CeO(2)-CuO nanocomposite performed well even at low concentration of 0.3 g L(-1), with a more than fifty-one times lower corrosion rate and twenty times higher polarisation resistance (R (p)) compared with unmodified coating. Nanocrystalline CeO(2) increased the R (ct) from 114 Ω cm(2) to 427.5 Ω cm(2) at 0.6 g L(-1), whereas the CeO(2)-CuO nanocomposite increased this value up to 3645 Ω cm(2) at 0.3 g L(-1). Enhanced corrosion resistance of these coatings was confirmed with an accelerated salt-spray test.