| Silicone coating is a kind of high temperature resistant coating which is widely used in chimney,boiler,combustion chamber,heat pipe and other high temperature equipments.The silicone resin will decompose and form brittle and loose inorganic-Si-O-Si-O-structure at high temperature.With the volume shrinkage,the coating porosity is caused,which seriously affects the protective performance of the coating.The marine atmospheric environment has the characteristics of high humidity and high salt content.In this environment,the high temperature corrosion of metal materials is more serious.The coating is not only required to have the pure high temperature resistance,but also to have the high temperature,humidity and salt spray corrosion resistance,with the functions of anti-oxidation and corrosion resistance.In this paper,based on the study of film-forming system of high temperature resistant silicone coating,nano modified silicone high temperature resistant anti-corrosion coating was prepared by nano modification and micro nano filling technology,and the protection mechanism of coating on austenite and martensitic stainless steel was discussed.The coating can be cured at room temperature by modifying the silicone resin with polyurethane resin.Based on the comprehensive investigation of the influence of the amount of curing agent on the curing performance and the conventional physical and chemical properties,the optimal amount of curing agent is determined to be 30 wt.%.On the basis of optimizing the film-forming system of organosilicon coating,eight series of coating formulations were designed with nano-TiO2,nano-Al2O3,nano-ZrO2,copper chrome black(CCB),glass powder,SiC,bimetal nano powder and NiCrAlY powder as the main fillers.The results show that,except for a few formulations,the coating has excellent flexibility and impact resistance.The coating can withstand 10000 hours of damp heat exposure corrosion and 5000 hours of artificial seawater corrosion.Among them,TiO2,SiC and Al2O3 coatings have excellent oxidation resistance at 600?.In the environment containing water vapor and solid NaCl at 600?,ZrO2 series has excellent high temperature oxidation and corrosion resistance.After oxidation at 650? for 1028 hours,the nano modified silicone coating with CCB as the main filler did not appear peeling and micro cracks,and the coating showed good high temperature stability and protective performance.The oxidation resistance mechanism can be attributed to the volume expansion caused by the high temperature oxidation of nano metal particles,which effectively compensates the pores caused by the thermal decomposition and volatilization of silicone resin,maintains the high density of the coating,and improves the protective performance of the coating.Adding a proper amount of nano ZrO2 ceramic particles to the nano modified silicone coating can significantly improve the high temperature oxidation resistance and corrosion resistance of the coating in high temperature,steam and solid NaCl environment.When the amount of nano ceramic particles is small,it has a bad effect on the high temperature corrosion resistance of the coating;when the amount of nano ceramic particles is too high,it has a bad effect on the peeling resistance of the coating;when the amount of nano ceramic particles is 20wt.%or 30wt.%,the coating has the best comprehensive performance. |
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