Study on Combination Mechanism of Pretreatment Layer in Pre-Coated Metal Sheets

Pre-coated metal sheets (PCM), as a popular product in modern coating industries, offer significant advantages such as simple processing, lightweight properties, and excellent manufacturability. The pretreatment layer within its coating system has a significant impact on overall corrosion resistance. In this study, through a comparative analysis of two chromate-free pretreatment systems, we conducted a thorough investigation into the combination of the pretreatment layer and examined the impact on the corrosion performance of pre-coated metal sheets. It was found that the phytic acid-based pretreatment layer enhances the adhesion between the primer and the substrate by forming strong chemical bonds with the primer layer, which effectively inhibits the lateral diffusion of corrosive media to the metal surface. Consequently, pre-coated metal sheets with the phytic acid-based pretreatment exhibit superior anti-foaming performance compared to the system using the silane-based pretreatment layer. This provides a new insight into the design and development of Cr-free pretreatment systems with better corrosion resistance performance.