Preparation and corrosion performance of aluminum-silicon composite siloxane sealing layer

The work aims to improve the corrosion resistance of the coating and study the effect of the ratio of aluminum silica sol and siloxane in the sealing agent on the sealing performance. Aluminum-silicon composite sol and methyltrimethoxysilane (MTMS) were used as the main raw materials to prepare inorganic-organic mixed sealing agent by sol-gel method, and seal the Cr3C2-NiCr thermal spray coating To explore the effect of different proportions of aluminum silica sol and siloxane in composite sealing agent on the corrosion resistance of the coatings. The phases, thermal stability and microstructure of sealed coatings were analyzed by X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA) and scanning electron microscopy (SEM). The corrosion resistance of the coating before and after sealing was studied by polarization curve and electrochemical impedance spectroscopy. The corrosion performance of the coating was further explored by full immersion corrosion test. The curing temperature of Al-Si composite sol was about 120 ℃, and the surface of the coating was smooth and dense after curing. The heat-resistance temperature of the sealing agent was around 300 ℃. The sealing agent had a good effect on pores of the sprayed coating. When the mass ratio of the Al-Si composite sol and the siloxane was 3:2, the coating had the best corrosion resistance. The self-corrosion current density and impedance were 8.671×10-6 A·cm-2 and 4593 Ω·cm2, respectively and the full immersion corrosion rate of the coating was 4.17×10-3 g/(m2·h). However, with the increase of the proportion of MTMS in the sealing agent, cracks appeared during the curing process, which decreased the corrosion resistance of the coating. Therefore, the prepared sealing agent has improved the corrosion resistance of the coating significantly, and the coating gets the best corrosion resistance at an MTMS content of 40%. © 2019, Chongqing Wujiu Periodicals Press. All rights reserved.