Preparation And Characterization Of Double Layer Ceramic Coating Based On 304 Stainless Steel Anticorrosion

Ceramic coating has excellent heat resistance and corrosion resistance for metal surface protection,especially under high temperature and high humidity conditions,which has been widely used.In order to broaden the application temperature range of 304 stainless steel plate,a double-layer ceramic coating was designed and fabricated by the combination use of epoxy modified silicone resin and hydroxy silicone resin as primer coating to enhance the high temperature adhesion,and by the use of silica sol-gel as top coating to enhance the hardness and corrosion resistance of the coating.In this work,a series of high performance coatings on the surface of 304 stainless steel substrate were studied.Firstly,the common high-temperature fillers TiO₂,Al powder,glass powder,Al₂O₃ and ZrO₂ as well as the common SAR-9,D0220,HYS-1 and SH-23 silicone resins were compared and analyzed.A combination use of ZrO₂ and Ba SO₄ filler as well as SAR-9 and SH-23 resin with different ratios was developed and optimized.The comprehensive properties of the coating,such as the thermal weight loss,adhesion,hardness,water vapor resistance,surface morphology,electrochemistry,etc.were tested and analyzed systematically.Based on all the results,the coating formulation was continuously improved,and the optimal ratio of silicone resin SAR-9 and SH-23 was determined.A primer coating was successfully prepared with excellent performance of high-temperature resistant and anticorrosive.The coating exhibitted no obscission and bubble after heat treatment at 450°C.The adhesion level and pencil hardness was 0 and 8H,respectively.Moreover,the coating had no obvious change after steam treatment for 2 hours.Furtheremore,instead of ZrO₂,TiO₂ was used as the main filler.Through thermalgravimetic analysis,electrochemistry,and contact angle analysis,it was concluded that the coating of ZrO₂ filler showed better heat resistance,while the coating of TiO₂ filler displayed excellent corrosion resistance.The sol-gel method was used to prepare the topcoat,and the influence of different proportions of silane and water was examined.Through contact angle test,acid and alkali corrosion test,electrochemical test and appearance comparison,it was determined that the molar ratio of TEOS:MTES is 3:1,the molar ratio of water to silane is 3.5:1.The coating exhibitted no obscission and bubble in Na OH and 5%HCl,the hardness reached 8H,and the polarization resistance Rp of the coating reached 167595?·(88)² in 3.5wt%Na Cl solution.Through the formation of Si-O-Si cross-linked structure,a better combination interaction between the substrate,primer coating and top coating was achieved.Finally,the double-layer coatings for 304 stainless steel were prepared,which exhibited excellent heat and corrosion resistance.