Anti-corrosive composite coatings based on PVB/ZnO:Co and PVB/HAP:Co

Recently we have developed polymer/ceramic composite coatings based on poly(vinyl butyral), hydroxyapatite and zinc oxide-based nanostructured powders (PVB, HAP:Co and ZnO:Co, respectively). Prepared composite coatings showed good both adhesions to metal and glass surfaces and camouflage properties, thus can be used to improve combat capability of military equipment. An essential demand of new materials in the military industry is to be multifunctional. Accordingly, the aim of this study was to examine corrosion activity of the PVB/ZnO:Co and PVB/HAP:Co coatings in saline solution as a function of immersion time. The ZnO:Co and HAP:Co nanostructured powders were synthesized by hydrothermal processing of a precipitate. To adjust optical properties, synthesized powders were annealed at 400, 800 and 1000 °C. Annealed powders were mixed with PVB: each powder was dispersed in ethanol with the aid of an ultrasonic probe, successively PVB powder was added in dispersion, in 10 wt.% regard to ethanol, and stirred on a mechanical stirrer to completely dissolve. Prepared solution was coated on stainless steel substrate and dried at room temperature for 72 hours to form solid coating. The corrosion activity of the coatings was measured by potentiodynamic polarization technique in the potential range from -0.8 to -0.2 V vs SCE, with the scan rate of 10mVs-1. The measurements were performed using a conventional three-electrode cell in 3% NaCl water solution as the electrolyte. Platinum foil, a standard calomel electrode (SCE) and coated stainless steel were used as the counter, reference and working electrode, respectively. We found that all examined coatings have lower corrosion activity than bare stainless steel or stainless steel coated with pure PVB. Differences in corrosion activity between the coatings are explained by different textural and optoelectronic properties of ceramic powders modified by the annealing procedure.