高耐腐蚀性三价铬彩色钝化膜制备工艺优化及膜层性能研究

Process Optimization and Peformance Evaluation of High Corrosion Resistant Trivalent Chrome Iridescent Passivation Film

为进一步提高三价铬彩色钝化膜的性能,在无机钝化液中加入有机硅树脂,制备了一种新型高耐蚀性能三价铬彩色钝化液。该钝化液可以在镀锌板表面形成有机-无机复合钝化膜,通过红外光谱仪分析钝化膜结构,采用扫描电镜观察钝化膜微观形貌,用能谱仪分析钝化膜的微观组成,采用电化学试验、中性盐雾试验对钝化膜耐蚀性能进行表征。以正交试验对三价铬彩色钝化液组分进行了优选,以单因素试验研究了钝化温度、钝化液pH值、钝化时间等钝化条件对钝化膜耐腐蚀性能的影响。结果表明:最佳钝化液成分为硫酸铬10.00 g/L,硅树脂12.50 g/L,硝酸钠4.00 g/L,硝酸镍1.25 g/L,氯化钠2.00 g/L;最佳钝化条件为温度30℃,时间150 s,pH值1.8;以最优条件制得的钝化膜色彩鲜艳,耐蚀性能突出,耐中性盐雾腐蚀时间达196 h。

A new kind of trivalent chrome iridescent passivation solution with high corrosion resistant performance was prepared through adding silicone resin into inorganic passivation solution. A color passivation film on the surface of galvanized sheet formed in the passivation solution, and infrared spectrometer was employed to study the passivation film structure. The morphology and composition of film were analyzed by scan- ning electron microscope and energy dispemive spectroscope, and the corrosion resistance was evaluated by electrochemical test and neutral salt spray test. Furthermore, the composition of trivalent chromium passivation solution was optimized by orthogonal test, and the effect of passiva- tion temperature, pH value and time on corrosion resistance of passivation film was studied by single-factor experiment. Results showed that the optimal composition was as follows ： Cr2（ SOn ） 3 10.00 g/L, silicone resin 12.50 g/L, NaNO3 4.00 g/L, Ni（ NO3 ） 2 1.25 g/L, NaC1 2.00 g/L; 30 ℃ , 150 s, pH= 1.8. The passivation film prepared under the optimal conditions had iridescent appearance and excellent corrosion resist- ance, and neutral salt spray corrosion time was up to 196 h.