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将热浸镀Galfan钢板浸入含有20 g·L-1La(NO3)3·6H2O,10 m L·L-1H2O2,0.1 g·L-1Na F的处理液中,在70℃下处理10 s~30 min,从而在其表面获得镧盐转化膜。采用扫描电子显微镜(SEM)观察膜层的微观形貌,能谱仪(EDS)分析膜层的化学成分。采用中性盐雾试验和电化学极化曲线来研究膜层的耐蚀性能。结果表明,镧盐转化膜在晶界或相界等活性区域优先成膜并迅速生长,膜层形成不均匀。随着处理时间的延长,镧盐转化膜逐渐增厚,膜层的裂纹变多、扩大并脱落;膜层主要由Zn,Al,O和La元素组成。与未处理的热浸镀Galfan镀层相比,镧盐转化膜的腐蚀电流密度显著降低,极化电阻显著提高,基体耐腐蚀性能明显提高。
The Galvan steel plate immersed in the treatment solution containing 20 g · L-1La (NO3) 3 · 6H2O, 10 m L · L-1H2O2, 0.1 g · L-1Na F at 70 ℃ for 10 s ~ 30 min, thereby obtaining a lanthanum conversion coating on the surface thereof. The microstructure of the film was observed by scanning electron microscope (SEM) and the chemical composition of the film was analyzed by energy dispersive spectrometer (EDS). Neutral salt spray test and electrochemical polarization curve to study the corrosion resistance of the film. The results show that lanthanum conversion coatings preferentially form and grow rapidly in the active region such as grain boundaries or phase boundaries, and the film formation is not uniform. With the prolongation of treatment time, lanthanum conversion coatings gradually increased, the cracks in the coatings increased, and expanded and dropped off. The coatings mainly consisted of Zn, Al, O and La. Compared with untreated galvanized Galfan coating, the corrosion current density of lanthanum conversion coating was significantly reduced, the polarization resistance was significantly increased, and the corrosion resistance of the matrix was significantly improved.