Study Of Pretreatment Layer Of Protective Painting System On Galvanized Steels

Galvanized steel is widely used in various fields as a kind of metal material because of its long life span of more than ten years.As to the air pollution in recent ten years,the working condition of galvanized steel deteriorates seriously.In the heavily polluted areas,such as the industrial concentrated areas with polluted atmosphere,t The coastal areas corroded by salt,the confined space filled with corrosive gases,the galvanized steel applied in industry is facing a great safety challege,and its practical service life is far less than the design life.Coating system is widely applied in order to protect the Galvanized steel parts from corrosion,and its validity has been proved.Because simple hot-dip galvanized steel cannot fully fulfill the anti-corrosion requirements under the harsh environment,the coating system is applied on the surface of galvanized steel substrate.the proposed coating system focuses on the surface treat technology of Galvanized steel to improve the viscosity between the steel surface and the organic coating.The main contents of this thesis are listed as follows:(1)The barrier silane BTESPT(bis-1,2-[triethoxysilylpropyl]tetrasulfide),functional silane GPTMS(epoxypropyltrimethoxysilane),and the two silane compounding as an organosilane film pretreatment layer to construct a metal/silane film/epoxy coating protection system.The experiment shows proves no difference of coating systems constructed by barrier silane and functional silane if the coating films are complete.However,once the coating film is broken,the protecting properties of functional silane are better,due to its good adhesion with subsequent coating.(2)The electrodeposition of inorganic silica film was constructed as a pretreatment layer on the surface of galvanized steel.Attempts were made to pre-load the corrosion inhibitor on the silicon dioxide film.As the material is coarse and porous,the silicon dioxide film forms an inter-inserted structure with the subsequent coating,and the adhesion between the coating film and the substrate is significantly improved.Due to the porous structure of silica,considerable amount of corrosion inhibitor can be loaded on it to improve the protecting performance.Repairing can be carried out by the inhibitor layer once the coating film is damaged,as shown in the experiments.Thus the coating system can be enhanced whether the coating film is damaged or not.When the corrosion-inhibiting agent is applied on the surface of the galvanized steel substrate,the coating system with active protection performance is constructed,and the protection performance is further improved.(3)A coating system was constructed using a GPTMS silane-modified electrodeposited silica film as a pretreatment layer.The combination of chemical bonding(GPTMS bonding with subsequent coatings)and physical inlay(silica porous structure)allows the technology to further enhance the adhesion of galvanized steel to subsequent coatings and the whole coating system.