固化温度对硅酸钠防锈膜性能的影响及其成膜机理

将钢板浸入到硅酸钠溶液中,取出后在不同温度下固化,形成连续透明的保护膜。通过露天耐候试验、塔菲尔极化、中性盐雾试验(NSS)研究了不同温度固化后硅酸钠膜的耐蚀性及耐溶性能,采用扫描电子显微镜(SEM)、傅里叶红外仪、热重(TG-DSC)等对硅酸钠防锈膜的表面形貌及微观结构进行了分析,并对防锈膜的成膜机理进行了探讨。结果表明:高温固化的硅酸钠防锈膜的耐腐蚀性能优于低温固化的硅酸钠膜,200℃固化的硅酸钠膜耐常温水溶解效果最好;随固化温度的升高,膜体系主要发生了2Q3→Q4+H2O,2Q2→Q3+H2O,Q2+Q3→Q3+Q4+H2O等反应,导致膜层中含4个桥氧原子的硅氧四面体(Q4)不断增多,从而形成了致密、均一的三维网状结构硅酸钠膜,膜层耐蚀性更好。

Effect of Curing Temperature on Corrosion Resistance of Sodium Silicate Conversion Antirust Coating

Steel sheets were immersed in the solution of sodium silicate,followed by curing at different temperature to form continuous transparent protective coatings.The corrosion resis-tance of the sodium silicate coatings obtained after curing at different temperature was evaluated by open-air test,Tafel polarization test and neutral salt spray test,and their resistance against dissolution in water was examined.In the meantime,a scanning electron microscope,a Fourier transform infrared spectrometer and a thermal analysis instrument were performed to analyze the morphology and chemical structure of the sodium silicate conversion antirust coatings.Moreover,the film-formation mechanism of the antirust coatings was discussed.Results indicate that the sodium silicate conversion coatings obtained after curing at high temperature possess better corrosion resistance than those obtained after curing at low temperature,and the antirust coating cured at 200 ℃ has good resistance against dissolution in water.Chemical reactions of the antirust coatings were involved at increased temperature,leading to continuously increased amount of tetrahedron with four bridging oxygen.As a result,compact and uniform antirust coatings with three dimensional network-like structure were formed,and the corrosion resistance of the antirust coatings was increased.