Causes and Solutions of Flash Rust on Water-based Industrial Paint Films

Flash rust occurs when water in the coating contacts a metal surface (iron, nails, steel). It is more likely in damp conditions and on corroded or freshly activated steel. Causes: 1) incomplete pre-treatment leaving rust or scale; 2) low temperature / high humidity or overly thick film slowing drying and causing flash rust; 3) dissolution and deposition of iron compounds prolonging water-substrate contact; 4) defects in the paint formulation itself. Solutions: 1) clean the substrate thoroughly, no obvious rust or scale; 2) improve temperature/humidity, increase ventilation, accelerate drying, apply thin multi-coats; 3) if flash rust appears, after the film dries, lightly sand and apply another anti-corrosion coat to stop rust migration; 4) adjust the water-based paint formulation. As the saying goes, 'three parts coating, seven parts application' - proper construction is decisive.