Silanization technology for pre-treatment of Metal Pails surface coating
Silanization technology for pre-treatment of Metal Pails surface coating
1 Mechanism
Silane is a kind of organic/inorganic hybrid containing silicon group, which is usually hydrolyzed in aqueous solution to form Si-OH, and dehydrated and condensed between Si-OH to form oligomeric siloxane containing Si-OH; Si-OH in oligomer OH reacts with the Me(OH)n group (Me represents metal) on the metal surface and rapidly adsorbs on the metal surface. On the one hand, silane forms a Si-O-Me covalent bond on the metal interface (the force between the covalent bonds can reach 700 kJ/mol), and the bonding force with the metal is very strong; on the other hand, the remaining silane The silane film with Si-O-Si three-dimensional network structure was formed on the metal surface through the polycondensation reaction between the molecules and SiOH groups. The silane film is combined with the coating (electrophoretic paint or powder coating) through the cross-linking reaction to form a strong chemical bond (the silane film has good compatibility with the coating). In this way, a stable film structure is formed between the substrate-silane-coating layer through chemical bonds. This is why silane treatments can replace paint phosphating and chrome treatments.
The silane film can also play the role of closing a large number of micropores on the phosphating film to form a continuous, complete and dense composite film. The composite film has extremely strong corrosion resistance (phosphating film plus silane film of hot-dip galvanized sheet is resistant to neutral salt spray for 5 cycles, the surface is not corroded, which is significantly better than that of single phosphating film and single silane film), and can Maintain the microscopic surface roughness of the phosphating film (because the silane film is extremely thin, with a thickness of only 200-300 μm).
2 Features
The application of silanization technology to metal surface treatment has significant advantages.
2.1 Strong adaptability to metal materials
Silanization technology is suitable for the treatment of cold-rolled steel sheets, galvanized steel sheets, aluminum materials, zinc-aluminum alloys and other metal substrates, among which the treatment effect of galvanized steel sheets is slightly worse. It can realize the co-linear production process of various substrates, and the treatment effect is related to the treatment method (the effect of silane spraying is better than that of dipping, because the latter has more grooves).
