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1、锌镀层的铬酸钝化过程,是在固—液(金属—溶液)界面上进行的多相化学反应过程。低铬钝化的铬酐浓度小,更是必须考虑扩散作用对钝化过程的影响。2、表面活化剂是铬酸钝化液形成彩色钝化膜的必要条件。氯离子和硫酸根离子是有效的活化离子。常用的表面活化剂有食盐、氯化铵、硫酸、硫酸钠和硫酸锌等,其添加量须随六价铬浓度的提高而相应增加,随六价铬浓度的降低而相应减少。在低铬钝化中,卤素离子(Cl~-、Br~-、I~-)都表现出活化剂的作用,其中尤以氯离子为佳。它使钝化时成膜速度加快,钝化膜色彩鲜艳,给合力好。卤素离子和硫酸根离子的作用是:在它们存在下,六价铬难以使锌表面形成保护性氧化膜,从而使界面上锌和六价铬的反应迅速进行,界面上PH值迅速升高,从而形成一定厚度的彩色钝化膜。3、低铬钝化和高铬钝化是有内在联系的,低铬钝化是从高铬二次钝化演变而来的,只要具备六价铬、活化剂和一定的酸度等条件,都可以产生彩色钝化膜。但是两者在铬酐浓度、酸度和成膜方式上又有区别。下列低铬钝化配方是有效的:铬酐5克/升,氯化钠2.5—3克/升,硫酸0.3—0.5毫升/升。4、总结并讨论了铬酐浓度、活化剂及其浓度、酸度(或PH值)、温度、浸渍时间(液相成膜时间)和工件与钝化液的相对运动等因素对低铬钝化的影响,并
1. Chromic acid passivation process of zinc coating is a multi-phase chemical reaction process at solid-liquid (metal-solution) interface. Chromium passivation of low-chromium chromic concentration is small, it is necessary to consider the effect of diffusion on the passivation process. 2, the surfactant is chromic acid passivation solution to form the necessary conditions for color passivation film. Chloride and sulfate ions are effective activating ions. Commonly used surfactants are salt, ammonium chloride, sulfuric acid, sodium sulfate and zinc sulfate, the amount to be increased with the hexavalent chromium concentration increased accordingly, with the reduction of hexavalent chromium concentration and a corresponding reduction. In the passivation of low chromium, the halogen ions (Cl ~ -, Br ~ -, I ~ -) all show the role of activators, especially chloride ion is better. It makes the film passivation speed, passivation film colorful, to work together well. Halogen ions and sulfate ions in the role: in their presence, hexavalent chromium is difficult to form a protective oxide film on the surface of zinc, so that the reaction of zinc and hexavalent chromium interface rapidly, the interface rapidly increased PH value, Thus forming a certain thickness of the color passivation film. 3, low chromium passivation and high chromium passivation is intrinsically linked, low chromium passivation is evolved from the high chromium secondary passivation, as long as there is hexavalent chromium, activators and certain conditions such as acidity, are Can produce color passivation film. However, the two are different in the concentration of chromic anhydride, the acidity and the film forming method. The following low chromium passivation formulations are effective: 5 g / l chromic anhydride, 2.5-3 g / l sodium chloride, 0.3-0.5 ml / l sulfuric acid. The effects of chromic anhydride concentration, activator and its concentration, acidity (or PH value), temperature, immersion time (liquid phase film forming time) and the relative movement of workpiece and passivation solution on the low chromium passivation The impact, and