Chromate passivation process for hot-dip zinc
Nov 10,2020
Hot galvanizing is the most common and economical process in the surface anti-corrosion process of steel materials. Hot dip zinc products are widely used in construction, automotive, communications and other fields. With the increasing market demand for hot-dip zinc, it also promotes the continuous upgrading and improvement of hot-dip zinc process, so that the quality of hot-dip products can be improved.
Chromate passivation is an important part of hot dip zinc process. The corrosion resistance of hot-dip zinc products can be improved by passivation treatment. Chromate passivators usually consist of trivalent chromium or hexavalent chromium chromate, an activator. The surface color after passivation varies according to the length of passivation, and is usually natural or multicolored. The corrosion resistance of the passivation film is also affected by the surface roughness of the hot-dip zinc layer. The porosity of the passivation film obtained by passivation treatment on the smooth surface of the coating is low, and its corrosion resistance is better.
Chromate passivators used in hot-dip galvanizing can be roughly divided into two categories. One type is water washing type, which is passivated after hot dip zinc, and then washed and dried. The other is no water wash type, hot dip zinc after passivation treatment, and then directly dried. The main difference between these two passivators is that the latter is more environmentally friendly, almost no chromate wastewater, and the production line structure is simpler to reduce costs. For example, the HKS-RD trivalent chromium passivator of Dazhi Chemical is waterless, which can be dried at 50-120 ℃ after dipping or spraying at room temperature. The product has good stability, does not contain hexavalent chromium and meets the requirements of EU RoHS standard, and does not generate slag in production. Passivation solution can work with different concentrations according to different corrosion resistance requirements. According to the laboratory data, the neutral salt spray test can reach 300H without white rust when the stock solution is used.
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CONTACT US
Guangdong Dazhi Chemical Technology Co., Ltd
Email: sales@dazhichem.com
Phone/WeChat: 86-18520125168
Address: No.1 Tianyuan East Road, Yonghe Economic Zone, Huangpu District, Guangzhou City
