Development of Zn–ZrB2 nanocomposite coatings for wear, corrosion resistance and microstructure enhancement of carbon steel in saline environment

Nanocomposite coatings are increasingly being used in marine industries to enhance the performance of carbon steel. However, while some of these coatings deteriorate rapidly with time when in continuous contact with contaminants in the saline environments, others are relatively stable. This work was therefore designed to examine the mechanical properties, corrosion resistance and microstructure characteristics of coatings on SAE-1020 carbon steel. After preliminary runs of the experiment, coated samples were developed containing ZrB2 nanoparticles of 7 and 13 g L−1, at cell voltages of 0.3 and 0.5 V, and at a constant temperature of 45 °C. The corrosion rate of the coated samples was investigated in 3.50 wt.% NaCl solution using potentiodynamic polarization technique in accordance with ASTM standard, while a pin-on-disc tribometer was used to determine the wear volume. The result of the potentiodynamic polarization test indicated that there was an enhancement in corrosion resistance. A reduction in corrosion rate from 9.7425 to 0.2439 mm year−1, highest coating efficiency of 97.5%, highest polarization resistance of 675.65 Ω and an extremely low current density of 2.10 × 10–5 A cm−2 were observed. These corrosion property values indicated significant protection of the carbon steel’s active sites. The wear volume was also observed to have reduced from 0.00508 mm−3 for the uncoated carbon steel to a minimum value of 0.00285 mm−3 for the 0.5Zn-13ZrB2 (at 0.5 V with 13 g/L ZrB2) coated steel, which was ascribed to the dispersion-strengthening and self-lubrication ability of the ZrB2 nanoparticles.