Salt Spray Corrosion Mechanism and Anti-Corrosion Optimization of Powder Coatings

Coastal areas, marine engineering, chemical industrial parks and port equipment are in high-salt, high-humidity and high-corrosion environments for a long time. Salt fog contains a large amount of chloride ions, which have strong penetration and corrosive ability. Ordinary industrial powder coatings can only maintain short-term anti-corrosion effect in conventional environments. After long-term salt spray erosion, chloride ions will penetrate the coating film to contact the metal substrate, causing electrochemical corrosion, resulting in coating blistering, bottom rust, peeling and failure, seriously shortening the service life of equipment and facilities. Therefore, improving the salt spray resistance of powder coatings is the core demand of heavy-duty anti-corrosion industrial coating.

The main factors affecting salt spray resistance include coating compactness, film thickness, substrate pretreatment quality and formula anti-corrosion performance. Insufficient film thickness is the most common cause of salt spray failure. Too thin coating cannot form a dense protective barrier, and salt fog penetrates quickly. Poor substrate pretreatment, residual oil and rust spots will form local corrosion weak points, causing concentrated corrosion and local blistering. Ordinary formulas lack anti-corrosion functional fillers, with poor ion isolation ability and cannot block chloride ion penetration.

Standardized pretreatment and film thickness control are essential auxiliary guarantees. Strict pickling, degreasing, phosphating and passivation processes are required before spraying to completely remove surface oil, rust and oxide layers, and form a uniform passivation film on the metal surface to enhance the bonding force and anti-corrosion foundation. For heavy-duty anti-corrosion scenarios, the coating film thickness is strictly controlled above 120μm to ensure sufficient barrier thickness and completely block salt fog penetration.