Role of zinc and tin coatings via modified hot-rolling process for corrosion performance of steel rebar in simulated seawater

In this study, a novel technique is developed to enhance the corrosion resistance of steel rebars by spraying-by-spraying metallic nanopowders of zinc and tin onto the surface of hot-rolled steel. After embedding in a concrete mixture, the coated and uncoated steel samples are immersed in a 3.5% NaCl solution for 28, 56, and 90 days at various temperatures (298, 308, and 318 K). Surface morphology and structural characterization are investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD), confirming the formation of uniform, dense coatings with fine-grained crystallinity. The zinc coating exhibited a surface roughness of 18.82 nm and a mean particle diameter of 87.71 nm, while the tin coating achieved an even more compact structure with a surface roughness of 8.141 nm and a finer particle diameter of 33.15 nm. Electrochemical tests revealed that the best corrosion protection is achieved by the tin-coated steel, with a maximum inhibition efficiency of 96.53% at 298 K after 28 days, followed closely by the zinc-coated sample at 96.47% under the same conditions. Electrochemical impedance spectroscopy (EIS) analysis revealed that the highest solution resistance (15,129Ω. ) and Warburg impedance (26,632 Ω. ) are for the tin-coated sample at 298 K after 56 days, while Zn-coated samples recorded values of (11,897Ω· ) and (5.432 1015 Ω· ), respectively. These findings confirm the effectiveness of the proposed coating method in significantly improving corrosion resistance and service life of reinforced concrete structures in chloride-contaminated environments.