Research On High Temperature Corrosion Behavior Of Nano-modified Organosilicon Coating

Silicone coatings are widely used in chimneys,smoke exhaust pipes,combustion chambers and other equipment used in high temperature environments.The organosilicon resin will undergo pyrolysis above 200°C to form a-Si-O-Si-structure with good high-temperature resistance,but the pyrolysis will also lead to volume contraction of organic components and the formation of oxidation diffusion channels such as pores,causing coating failure.In this paper,nano-modified organic silicone coating was prepared by adding active fillers and high temperature resistant fillers.The prepared high temperature and thermal corrosion resistant nano-modified organic silicone coating was applied on the surface of 304 stainless steel which was used as the substrate,and the protective mechanism of the modified organic coatings is discussed and analyzed.The modified silicone coatings were prepared by changing the ratios of active fillers（nano-Al,nano-Ti）and high temperature resistant fillers（nano-ZrO₂,nano-Al₂O₃,SiC and low melting point glass powder）,and their oxidative corrosion behaviors were tested under 600℃,solid sodium chloride and water vapor environment at 600°C,400℃cyclically alternate corrosion environment.The results showed that the different filler ratios showed different antioxidant behaviors at 600℃,and the high pilling-bedworth ratio（PBR）of the active fillers would easily lead to the thermal mismatch between the coating and the substrate and thus the spalling occurs;the mass ratios of nano-Al,nano-Zr O₂,nano-Al₂O₃,Si C and low melting point glass powder were 10:7:3:7:3,the oxide scale produced by 304 stainless steel was only 0.7～0.8μm after oxidation at 600℃for 1000h,with the best high temperature oxidation resistance performance;the coating was tested at solid sodium chloride and water vapor environment at 600°C for 400h and 400℃cyclically alternate corrosion environment for 15 cycles,and the macroscopic morphology showed that the coatings all spalled.Good performance of nano-ZrO₂,nano-TiO₂,SiC and copper-chromium black were selected as the main fillers for the preparation of silicone coatings by neutral salt spray experiments and tested under solid sodium chloride and water vapor environment at 600°C and 400℃cyclically alternate corrosion environment.The results showed that:the oxide scale thickness of 304 stainless steel formed after 400h oxidation in solid sodium chloride and water vapor environment at 600°C was 14.3μm,and the oxide scale thickness formed after 36 cycles in 400℃cyclically alternate corrosion environment was 7.8～11.3μm;The nano-modified silicone coating with 5wt.%nano Zr O₂,the oxide scale generated at 600℃solid sodium chloride and water vapor environment for400h was only 0.86μm,and no oxide scale was observed in 36 cycles under 400℃cyclically alternate corrosion environment;the nano-modified silicone coating with Si C as the main filler,generated a large number of holes and oxide scale under 600℃solid sodium chloride and water vapor environment for 400h.In the 400℃cyclically alternate corrosion environment,no obvious holes and oxide scale were found in 15 cycles of coating,and a large number of holes were gener-ated in 36 cycles of coating.The nano-modified organosilicon coating achieves long-term service in the 600℃,solid so-dium chloride and water vapor environment at 600°C,400℃cyclically alternate corrosion envi-ronment.