The Anti-corrosion Study On Account Of The Primer Of Coach Body

In the last 10 years, China's bus industry has been developed rapidly. The total production has been ranked first in the world. The overall level of bus coating has made considerable progress, but the gaps still exist in the level of bus anti-corrosion. As the standard of people's living improves, the demand of the user becomes rationalization and specialization gradually. The anti-corrosion performance and surface coating quality for the bus have become two important factors on market competition.According to the special investigation of anti-corrosion that carried out in 2006 in Hainan and the state of several different bus models of main current domestic bus companies that runs in Hainan market, nearly 65% of the city buses appear partial corrosion after driving a year, it is the same for 40% touring buses after two years. The bus is formed by various parts of metal materials and nonmetal materials. The bus corrosion has diverse forms, complicated mechanism and great harmful dangers. It not only lowers bus life, but also easy to reduce the mechanical strength, causing leakage of the container parts and loss of function for some components, leading to the whole bus lost some functions to varying degrees. It affects the normal operation for the user and increases maintenance cost, even lead to personal safety. The result shows that failure of the surface coating is the main reason for the bus body corrosion.The corrosion resistance of coatings and good adhesion between the coating and substrate and matching coatings are the foundation of coating protection. The corrosion resistance of coating is decided by the composition of the paint, mainly by the combined result of film-forming resin, promoter and pigments. The coating adhesion is closely related with the characteristics of the substrate, including the surface cleanliness, roughness, porosity. Studies have shown that 80-90% of early failure of the coating is due to improper surface pre-treatment. At the same time, the coating adhesion is related to coating characteristics, primarily on the performance of the permeability of the coating to the substrate, wettability and the interaction with the substrate coating. The macro defects of the coating (such as the larger pinholes, cracks and visible cracks and other defects in general) often throughout the coating to the substrate surface. The reasons are more concerned with the construction process.Vehicle based primer coating, its main function is anti-corrosion. The performance of paint corrosion resistance, the adhesion between primer and body, the thickness of paint and uniformity are the key factors that lead to coating failure. Pre-treatment is the basis of primer. The quality of pre-treatment has direct impact on adhesion and corrosion resistance between the primer and bus body.This subject mainly studies the influence factors of anti-corrosion primer,and explores the way of improvement to improve the surface treatment before cleanness and phosphating film corrosion resistance, with the premise of paint changeless to improve the coating thickness and primer tight, improve primer, improve their formula primer and improve corrosion resistance performance of galvanized sheet primer on adhesion.The study based on the bus body primer of existing technology of our company, separately from three aspects of once process, primer methods and primer to analyze the factors of influencing primer formula of corrosion resistance, explore the way of improving adhesion and primer and body primer corrosion resistance.1. In the pre-treatment of body skimmed technology, increases the degreasing manual pretreatment, mechanical spraying and body movement, with mechanical mechanism to improve the adhesion and primer phosphating film.2. In the main factors of affecting phosphating film corrosion resistance and adhesion phosphating film P ratio directly reflects the phosphating film and film compound layer adhesion and corrosion resistance. To improve the P ratio, adjusting formula and construction parameters can improve the galvanized sheet phosphating film adhesion make the phosphating film compound with primer layer by layer,and salt spray test increased to 400 hours from 350 hours.3. The coating thickness directly affects the coating corrosion resistance. Using manual method of electrostatic spraying,adjusting the best construction parameters,sampling results show that the paint in the changeless circumstance can improve primer thickness of 50-70%, any template fog-corrosion improved from original 350 hours to 480 hours.4. Physical antirust pigment can influent epoxy polyamide a lot on the corrosion resistance.using ferric oxide, three aluminum tripoly phosphate, mica powder, can make the paint fog-corrosion improved from 350 hours to 500 hours.5. The epoxy polyamide curing agent added more or less 10%(curing agent content) silane coupling agent can make the adhesion between epoxy polyamide and steel improved to 0 level.