Passivation treatment of zinc alloy
域 ,但镀锌层在湿热环境中易发生腐蚀,为了进一步提高镀锌层的耐蚀性,必须对其进行钝化处理。 Electrogalvanization is widely used in automobiles, building materials, household appliances and other fields , but the galvanized layer is prone to corrosion in hot and humid environments. In order to further improve the corrosion resistance of the galvanized layer, it must be passivated. The traditional treatment method is passivation with chromate. This treatment method has the advantages of simple process, good film adhesion, beautiful appearance, high corrosion resistance, and self-repairing ability. ,因此近年来世界各国都在努力研究镀锌层的无铬钝化处理工艺,主要包括无机类钝化和有机类钝化。 However, because the chromate passivation solution contains the carcinogen hexavalent chromium, which poses serious harm to people and the environment , in recent years, countries around the world have been working hard to study the chromium-free passivation process of galvanized coatings, mainly including inorganics. Passivation and organic type passivation. Inorganic passivation processes mainly include molybdate passivation, tungstate passivation, silicate passivation, rare earth metal passivation, etc .; organic passivation processes mainly include phytic acid passivation, tannin passivation, Diaminotriazene (BAT4) and its derivatives passivation, acrylic resin passivation process, etc. Among them, the molybdate passivation process is the main research direction of chromium-free passivation. This paper is devoted to the research of chromium-free blue-white passivation process of galvanized layer, using inorganic salt organic acid co-passivation technology, using sodium molybdate and sodium phosphate as the main salt of passivation solution, and compounding with organic acid. This passivation solution can form a blue-white passivation film on galvanized steel, and the corrosion resistance of the passivation film is equivalent to that of chromate passivation film. It is expected to replace chromate passivation in galvanization passivation.
The passivation of zinc and zinc alloy mainly refers to the surface passivation of products such as galvanized layer, hot-dip galvanized layer and zinc alloy castings. Due to the lively chemical properties of zinc, it is easy to be corroded in various environmental media to generate white rust. As a result, the surface rust is damaged, and the decorative performance of the surface is also damaged. Therefore, products with zinc and zinc alloys as the body or zinc as the surface coating must be passivated.
Passivation with chromate or dichromate passivation, can also passivate with other metal inorganic salts or organic salts. The acid passivation can make the surface of zinc form an anti-rust protective film, improve the appearance of gloss, and enhance its decorative performance and effect. The specific approach is as follows. (1) Improve the corrosion resistance of zinc. The zinc surface is treated with chromate to form a corrosion-resistant anti-casting film layer to prevent zinc from contacting with external corrosive media and produce white corrosion products. This is the most widely used and most important. (2) Improve gloss and decorative performance. By polishing the concentrated chromate solution, the zinc surface is chemically polished to form a bright surface, which improves its gloss and decorative properties. The passivation film can also show different colors, especially white passivation can obtain a light blue passivation film, which is approximately chrome-plated, and has a good appearance decoration. It can also passivate into beautiful film layers such as military green or black. (3) The bottom chromate passivation film coated with light or color has good adsorption and adhesion. The chromate-treated passivation film can be dyed in a variety of colors, allowing the coating to be used for a variety of decorative purposes. The chromate passivation film has strong adhesion to the coating, and the coating is easily absorbed on the passivation film. In order to improve the adhesion and rust prevention of the concrete, a chromate passivation film can be used as the bottom layer of the paint.
→不锈钢喷丸(除氧化皮,脱模剂)→除油→两道水洗→两道水洗→钝化(浸泡4-6分钟)→两道水洗→干燥（热风吹,烘,温度：60-65℃）----包装出货1.开缸方法:加入4份的纯水，再加入1份钝化液，搅拌均匀，检测PH值（新开缸一般不用调整，使用后一段时间用补加钝化剂或者用稀释硫酸或2%的氢氧化钠调整PH值），加热至操作温度后即可投产。 Zinc alloy passivation process process Zinc alloy → stainless steel shot peening (descaling, mold release agent) → degreasing → two water washing → two water washing → passivation (soaking for 4-6 minutes) → two water washing → Drying (hot air blowing, baking, temperature: 60-65 ° C) ---- Packing and shipping 1. Open the cylinder method: add 4 parts of pure water, then add 1 part of passivation solution, stir evenly, check the pH value (new Generally, no adjustment is needed to open the cylinder. After a period of use, the passivation agent is added or the pH value is adjusted with diluted sulfuric acid or 2% sodium hydroxide), and it can be put into production after heating to the operating temperature. 2. PH value control: With the progress of production, the pH value of the passivation tank liquid will continue to rise. At this time, you can use diluted sulfuric acid or concentrated passivation liquid (according to concentration analysis or consumption addition) to lower the pH value. During the debugging process, too much sulfuric acid was accidentally added, which caused the pH value to be too low. You can use 2% sodium hydroxide solution to increase the pH value to within the normal range. 3. Concentration control: It can be added according to the concentration titration analysis or consumption (1-3L concentrated solution / 100㎡ surface area). When a large area of yellow spots or white spots appear on the processed workpiece, it is invalid after adjustment. It is recommended to re-arrange the groove.
HWJ-604三价铬钝化剂，是由三价铬盐、有机酸、氧化、络合剂等配制而成，广泛应用于铝铸件、铜铝结合件和铝合金的表面钝化和涂装前处理，膜层呈无色至浅兰色或黄兰相同的五彩色，膜层均匀光亮，耐蚀性好，不含六价铬、铅、镉、汞等元素，为绿色环保产品，铬化膜非常均匀,且耐蚀性及附着力良好，可低温下处理.耐腐蚀性能强，处理时间短，沉渣极少，结晶致密，槽液稳定易维护、成本低等优点。 Huiweijia HWJ-604 trivalent chromium passivation agent is formulated from trivalent chromium salt, organic acid, oxidation, complexing agent, etc. It is widely used in the surface passivation of aluminum castings, copper-aluminum joints and aluminum alloys. The same five colors as the colorless to light blue or yellow blue of the film before the coating. The film is uniform and bright, with good corrosion resistance. It does not contain hexavalent chromium, lead, cadmium, mercury and other elements. It is green and environmentally friendly. Products, chromate film is very uniform, and has good corrosion resistance and adhesion, can be processed at low temperature. Strong corrosion resistance, short processing time, minimal sediment, dense crystals, stable and easy maintenance of the bath, low cost and other advantages. Specially used for surface passivation of zinc, magnesium, aluminum and its alloys.
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