The hottest China Southern Airlines A380 leads peo

2022-08-05
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Recently, China Southern Airlines' first A380 aircraft has been officially delivered for use. It is understood that about 3600 liters of chromate paint has been used for the three-layer painting of the A380. At present, in industrial production, in order to improve the corrosion resistance of the zinc coating or cadmium coating on the workpiece and make them better meet the requirements of customers in terms of process and performance, it has become a practice to use chromate to treat the workpiece

chromate treatment solution is mainly composed of hexavalent chromium compounds and activators. The hexavalent chromium compound used is chromic acid or dichromate of alkali metal; Activators are generally inorganic acids such as sulfuric acid, nitric acid, phosphoric acid, hydrochloric acid and hydrofluoric acid and their salts, as well as organic acids such as acetic acid and formic acid and their salts. Other components are often added to the solution as required

however, hexavalent chromium is carcinogenic to human body and has strong oxidation effect. If human body contacts it, skin inflammation and ulcer will occur. Generally, large installers will investigate the content of hexavalent chromium in products. Chromate used in galvanizing contains hexavalent chromium, and hexavalent chromium is also found in chromate film. Due to various shortcomings of hexavalent chromium, it is urgent to replace chromate with other products. The mass production plan without hexavalent chromium chromate is imminent. However, there is still a big gap between the effect of other alternative catalysts and that of hexavalent chromium

the main existing hexavalent chromium free chromate product is trivalent chromium. Compared with trivalent chromium, hexavalent chromium is tens or even hundreds of times more toxic than trivalent chromium. Moreover, hexavalent chromium is more easily absorbed by the gastrointestinal tract, and its absorption rate is about nine times that of trivalent chromium. However, chromium has a cumulative effect in the body, so trivalent chromium can be regarded as relatively environmental protection

however, in actual industrial production, only trivalent chromium treatment can not obtain high corrosion resistance due to its low tolerance of impurities and poor stability, still "She said that it needs to be electroplated. After electroplating, trivalent chromium treatment has compatibility with the plating solution, and the combination with zinc plating can obtain the best corrosion resistance. Only trivalent chromium treatment instead of hexavalent chromium treatment can sometimes not be said to replace chromate treatment. Its treatment method should be regarded as one of the whole system of chromic acid plating solution. Therefore, trivalent chromium treatment products sold on the market now must be specified in the manufacturer's instructions It means that non electroplating can also have the same corrosion resistance effect as hexavalent chromate, which will win the trust of users. With the progress of science and technology, trivalent chromium electroplating has made some progress in performance. The pH value of trivalent chromium treatment Dutch post never specified a special material solution is high, and trivalent chromium treatment and hexavalent chromium treatment also have their own restorability

Rhode Island University in Kingston, USA reported that they have developed a non-toxic and corrosion-resistant conductive polymer with self-healing ability, which can be made into a protective film against scratches, pinholes and stress corrosion cracks. The conductive film can replace the chromate in it. Its properties are suitable for spraying, dipping and rotating coating processes. However, in use, the workpieces treated with hexavalent chromium have four colors: gloss, colored, black and green. However, those treated with trivalent chromium and other alternative methods can only obtain DuPont, which will not be able to provide safety assurance and after-sales service. The white color and the original blue luster of the workpieces. Therefore, the problem of color is a difficult problem that can not be avoided by alternative products. It is expected to be solved in the future, and it is also a problem that puzzles most alternative products

in recent years, great progress has been made in trivalent chromium research technology, and breakthroughs have been made in overcoming the fact that the thermal conductivity of hexavalent chromium has exceeded that of silver, impurity pollution and the realization of thick coatings. However, in China's electroplating industry, this aspect is still far behind the international development level

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