Application solution of silane coupling agent-560 in epoxy anticorrosive coating

The epoxy anticorrosive coating was modified with silane coupling agent-560, and a new epoxy coating with excellent anticorrosive function was obtained. The effects of silane coupling agent-560 coupling agent on the adhesion and salt spray corrosion resistance of epoxy anticorrosive coatings were studied, and the optimal dosage of silane coupling agent-560 coupling agent was determined. The results show that when the pigments, fillers and organic solvents are dehydrated and the amount of silane coupling agent-560 coupling agent is 1%, the adhesion and salt spray corrosion resistance of epoxy coating can be greatly improved. At this time, the pull off adhesion of epoxy coating is 16 3Mpa, salt spray corrosion resistance up to 720 H.
Silane coupling agent is a kind of compound that can improve the adhesion of polymer to inorganic substrate. One end contains groups that are easy to hydrolyze (methoxy, acetyl, etc.), which can react with hydroxyl or water on the surface of the metal matrix, and the other end contains organic functional groups (epoxy, amino, etc.) that can react with the resin. Therefore, organosilane coupling agents have dual reactivity, which can react with both polymers and inorganic substances, and form firm covalent bonds across the interface, so that the adhesion and durability of materials are improved.
Epoxy anticorrosive coating is a kind of protective coating with excellent corrosion resistance, which has been widely used in various fields of industrial anticorrosion. Adhesion to metal matrix and salt spray corrosion resistance are two important technical indicators to evaluate the performance of epoxy anti-corrosion coatings. How to further improve and improve the adhesion and salt spray corrosion resistance of epoxy anti-corrosion coatings to metal matrix and reduce the huge losses caused by metal corrosion to the national economy has become an important research topic in the field of industrial anti-corrosion. In this paper, the silane coupling agent-560 silane coupling agent was selected to modify the epoxy anticorrosive coating, and a new epoxy coating with excellent adhesion and salt spray corrosion resistance was prepared.
Main raw materials:
Silane coupling agent-560, content 98%, Changsha Zhongyi Chemical Co., Ltd; dispersant; Industrial grade, German BIC company; Zinc phosphate: industrial grade, Baoding Longyuan company; Aluminum tripolyphosphate: industrial grade, Guangxi Research Institute of chemical industry; Anti sedimentation agent: chemical pure, Taiwan Deqian company; Mixed solvent: industrial grade, self prepared; Amine curing agent: industrial grade, American shell company, epoxy resin: industrial grade, Yueyang Bahrain petrochemical company.
Dehydration of pigments and fillers: put the formulated amount of pigments and fillers in a drying vessel, bake it in an oven at 100 ℃ for 2 hours, and then seal it for use.
Dehydration of organic solvent: add a certain amount of anhydrous CaCl2 into a three port flask containing self prepared mixed solvent, disperse it for 20 minutes, and then stand for 2 hours, then filter the solvent, seal it for use.
Prepare epoxy anticorrosive coating, weigh epoxy resin, silane coupling agent, dispersant and mixed solvent according to the formula, disperse evenly, add pigments and fillers, disperse at high speed for 30 minutes, and grind to fineness ≤ 30 μ  m 。 Add other residual additives and an appropriate amount of mixed solvent to the prepared paint, adjust the viscosity for 100 ~ 120 s (apply 4 \. The prepared paint component and curing agent component are prepared into epoxy anticorrosive primer in the proportion of 6:1 (mass ratio).
Performance test
Spray the coating on the test plate according to the requirements of t1727-1992, test the adhesion according to the test method of coating adhesion (pull apart method) of t 5210-1985, and test the salt spray resistance according to t 1771-1991 (the requirements of the plate surface are crossed).
Results and discussion
Effect of silane coupling agent on film adhesion
Silane coupling agent can significantly improve the cohesion of the film and the adhesion to the metal matrix. The general formula of silicone coupling agent is x 3 Si (CH 2) n y. x group is a group that is easy to hydrolyze and can react with hydroxyl or water on the surface of metal matrix; Y group is an organic functional group that selectively reacts with resin [2]. For WD - 60 coupling agent, Y group is epoxy functional group. The surface of the clean steel plate substrate is not iron, but hydrated iron oxide. The X group of the reactive silane coupling agent forms a hydrogen bond with the hydroxyl group on the surface of the metal substrate (or the water layer on the surface), and then condenses to form an oxypropylene ring bond. In this way, under wet conditions, organic materials have high bonding strength to inorganic substrates.
Interaction between silane coupling agent and metal matrix
When silane coupling agent-560 is selected, the amount of silane coupling agent-560 has an impact on the pull off adhesion between epoxy anticorrosive coating and substrate. With the increase of the amount of silane coupling agent-560 coupling agent, the adhesion between film and substrate gradually increases. The dosage is 1 The adhesion reaches the maximum value at 0%, and then tends to stabilize. At this time, the adhesion of the film changes from 12 2 MPa to 16 3MPa 。 This is because the silane coupling agent-560 coupling agent not only forms a chemical bond with the surface of the metal matrix, its epoxy functional group also has a limited copolymerization reaction with the amine curing agent, forming an interpenetrating polymer network structure with the epoxy resin curing system, which greatly improves the cohesion of the paint film. When the amount of silane coupling agent-560 coupling agent increases, the IPN structure of the interface is also increasing, and the cohesion of the paint film increases accordingly. After reaching a certain amount (1.0%), due to the limited number of hydroxyl groups on the surface of inorganic metal matrix, the hydrogen bond and oxygen propylene ring bond formed by silane coupling agent-560 coupling agent and metal matrix reach a maximum value, so that the tensile strength also reaches the maximum value and tends to be stable.
Effect of silane coupling agent on salt spray corrosion resistance of film
The addition amount of silane coupling agent-560 in silane coupling agent is 1 Under the condition of 0%, the salt spray corrosion resistance of epoxy anticorrosive coating before and after adding coupling agent was investigated.
After 600 h neutral salt spray test of cold-rolled steel sheet sprayed with epoxy anti-corrosion coating, the cross section of the formula without silane coupling agent-560 coupling agent is seriously rusted (rust width > 2 mm, unqualified), while the cross section of the formula with silane coupling agent-560 coupling agent is only slightly rusted (rust width is about 1 mm). There are two main reasons for this: first, during the salt spray test, the paint film has a plasticizing effect due to water absorption after soaking at a certain temperature, and the coating has a relaxation phenomenon. After adding silane coupling agent-560 coupling agent, the adhesion between the paint film and the substrate is improved. After soaking, the adhesion point of the coating does not move due to the relaxation of the coating, but is still fixed at the original adhesion point, that is, the wet adhesion is good. On the other hand, due to the cross-linking reaction between the epoxy group on the silane coupling agent-560 coupling agent and the amine curing agent, the IPN structure is produced in the epoxy coating system, which further improves the density of the coating, greatly reduces the transmission rate of water, oxygen and inorganic ions, and effectively slows down the corrosion of corrosion factors on the substrate. Therefore, after adding silane coupling agent-560 coupling agent, the salt spray corrosion resistance of epoxy anticorrosive coating has been greatly improved.
Influence of water content of coating on coating performance
Silane coupling agents have high moisture sensitivity, are easy to hydrolyze to produce silanol (Si oh), and self condense to form siloxane oligomers, resulting in the loss of activity of silane coupling agents. Therefore, when applied to solvent based protective coatings, the components of the paint must be dry, and the solvent must be carefully selected, without water. General industrial grade organic solvents contain a small amount of water, and inorganic pigments and fillers will also contain a certain amount of water because of moisture. This study studied the influence of water in the paint on the performance of the paint by dehydrating the raw materials used.
Influence of moisture content of coating on coating performance when raw materials are dehydrated and silane coupling agent-560 is added, epoxy anticorrosive coating has the best adhesion and salt spray corrosion resistance. The test verified that the existence of water in the coating can lead to the loss of the activity of silane coupling agent. When the raw materials are not dehydrated, the salt spray corrosion resistance of epoxy anticorrosive coating is slightly reduced after adding silane coupling agent-560 coupling agent. It may be that the siloxane oligomer formed by hydrolysis and self condensation of silane coupling agent-560 coupling agent plays a plastic role in the film, reducing the crosslinking density of the film. Under the salt spray test conditions, the plastic siloxane oligomer will form corrosion points, It leads to the decline of salt spray corrosion resistance of the film. Conclusion silane coupling agent silane coupling agent-560 can significantly improve the adhesion to the substrate and salt spray corrosion resistance of epoxy anticorrosive coatings. When the raw materials are dehydrated, the dosage of silane coupling agent-560 is 1 At 0%, the pull off adhesion of the film to the substrate is 16 3Mpa, salt spray corrosion resistance time of 720 H.