Metal substrate surface treatment plays an important role in coating performance. The traditional surface treatment is divided into mechanical treatment and chemical treatment. Although the processes of phosphating and passivation in chemical treatment are mature, the cost of wastewater discharge and treatment is high. At present, the pretreatment of metal with silane coupling agent and phosphorus free film can not only improve the adhesion and anti-corrosion performance between the coating and metal matrix, but also meet the emission requirements of environmental protection.
The special structure of silane determines that it can form chemical bonding bond with metal (Si-O-Me, Me represents metal), so as to improve the chemical bonding between coating and metal matrix. In recent years, the role of silane coupling agent in metal pretreatment of anti-corrosion coating has been gradually recognized. Its process is simple, tire rubber additives are non-toxic, harmless, zero pollution, wide application range and low comprehensive cost.
Y-R-SiX3, Y is a group that can react with organic compounds such as vinyl, amino, epoxy and sulfhydryl. Coating additive R is a carbon chain with saturated or unsaturated bonds. X is a group that can hydrolyze alkoxy, acetoxy and halogen to form Si-OH.
(1) The Si-X group connected to silicon is hydrolyzed to Si-OH.
(2) Si-OH oligo siloxanes were synthesized by dehydration and condensation between Si-OH.
(3) Si-OH in oligomer forms hydrogen bond with OH on metal surface.
(4) In the process of heat curing, it forms covalent bond with metal with dehydration reaction.
The treatment process of silane coupling agent is as follows: degreasing, rinsing, rust removal, rinsing, silane coupling agent treatment, drying, coating. At present, this new process is more and more recognized by customers, and its application range and occasions are becoming wider and wider.
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