Hybrid Zinc Coating with CuO Nanocontainers Containing Corrosion Inhibitor for Combined Protection of Mild Steel from Corrosion and Biofouling

In this study, a multifunctional hybrid coating is designed for the combined protection of mild steel from corrosion and biofouling in aggressive salt water. This involves preparation of a pH-responsive-release system based on copper oxide (CuO) as a biocide, and the corrosion inhibitor Safranin loaded in polymeric nanocontainers by alternate adsorption of poly(acrylic acid) and poly(ethylenimine) on CuO nanoparticles in water solutions. By optimizing the conditions, i.e., pH and concentration, good stability of the suspensions and the loading amount of Safranin is achieved. The nanocontainers are electrodeposited as an intermediate layer in an ordinary zinc coating on steel (“sandwich-like” structure) from the water solution in order to minimize the effect of CuO dissolution. To highlight the role of Safranin in reducing steel corrosion, a second zinc coating containing CuO nanoparticles without a corrosion inhibitor is also examined. The surface morphology and corrosion behavior of the hybrid coatings are evaluated in a model corrosion medium (5% NaCl solution). Both coatings are found to improve the anticorrosion behavior of steel for a time interval of 55 days and at conditions of external polarization. It can be expected that the newly developed hybrid coatings would also demonstrate potential for marine applications due to the main characteristics of their components.