Influence of Zinc Coatings Mechanical Pre-Treatments for the Formation of Environmentally Friendly Passivation Duplex Anti-Corrosion Systems

The paper content is focused on the various evaluation methods of mechanical pre-treatment of hot-dip galvanized surface performed in order to increase the organic paint adhesion (both synthetic and waterborne). Emphasis was placed on low volatile organic compounds (VOC) values in coating systems. Corrosion degradation of the tested coatings was also monitored. The mechanical surface pre-treatment was performed using a standard technology, so-called sweeping, with synthetic corundum with F40 grain size (these samples served as a standard). Alternative methods that can be used in operations without blasting equipment were also investigated. These included regrinding with two different grain sandpapers (P40 and P100) and regrinding with a corrosion resistant steel brush (wire diameter 0.3 mm). The surface texture was evaluated in accordance with the ČSN EN ISO 4287 standard. Corrosion-mechanical resistance was evaluated by a pull-off adhesion test (according to the ČSN EN ISO 4624 standard) and in a salt spray environment (according to the ČSN EN ISO 9227 standard). Based on the obtained results, mechanical pre-treatment with a corrosion resistant steel brush and possibly P100 grit sandpaper can be recommended, as pre-treatment with these tools showed statistically the best corrosion-mechanical properties.