Aluminum alloy chromium-free five oxidation method
专栏:Industry information
1. The oxide film is colorless or milky white, and the water oxide film is γ-alumina-type alumina. The structure is fine, and the film is very stable at pH between 3.5 and 9, and can be used..........
1. The oxide film is colorless or milky white, and the water oxide film is γ-alumina-type alumina. The structure is fine, and the film is very stable at pH between 3.5 and 9, and can be used as the bottom layer of the paint. Superheated steam exceeding 100 °C is advantageous for the composition of the membrane, and the practical technique is to treat it in pure water at 75120 ° C for several minutes. In order to increase the film thickness, a porous oxide film can be obtained by adding ammonia water or triethanolamine to pure water. When the aluminum alloy is immersed in boiling water, the natural oxide film of aluminum will continuously thicken and finally reach 0.7 to 2 μm. The color of the oxide film treated by increasing ammonia water is white and the color is uniform. The maximum increase in ammonia is 0.3% to 0.5%.

2. Zirconium salt oxidation method

Zirconium-containing solution instead of chromate has been accepted by everyone for pre-treatment of aluminum-based surface. It is especially suitable for chemical conversion into film treatment before aluminum alloy parts are coated. It can increase the contact between coating and substrate, and improve corrosion resistance. Function, while the oxide film itself also has a certain anti-corrosion ability.

3. Titanium salt oxidation method

Titanium is very similar in nature to chromium and does not corrode in almost all natural environments. Its excellent corrosion resistance results from the continuous, stable and well-maintained oxide film layer formed on its exterior. Titanium's high reactivity and its strong affinity with oxygen make its metal appearance exposed to air or tidal temperature environment to form an oxide film. In fact, it seems that the chromate chemical oxide film is the same, only a small amount of oxygen or water (moisture) exists in the environment. Due to the strong affinity of titanium and oxygen, the damaged titanium oxide film can be self-corrected immediately.

4. Rare earth metal salt oxidation method

The rare earth metal salt chemical oxide film can replace the chromate chemical oxide film in the future, and the data can be treated by the dipping method. The treatment solution usually requires heating to produce a maintenance layer on the outer metal surface. Its corrosion resistance is based on the appearance of metal to form a rare earth oxide worship. At that time, the aluminum alloy rare earth treatment technology usually used a rare earth metal salt, an oxidizing agent, a film forming accelerator, and a coating solution composed of a film forming agent. Rare earth salts mainly refer to cerium salts such as CeCl3, Ce(NO3)3, Ce(SO4)2, (NH4)2Ce(NO3)6, etc. The film-forming accelerators are NaOH, HF, SrCl2, (NH4)2ZrF, etc. H2O2, KMnO4, (NH4)2S2O8, and the like. A disposal technique in which no oxidizing agent is added to the treatment liquid is a rare earth bohmite layer technique. This technique involves forming an aluminum alloy with hot water on its outer surface to form a bohmite layer and then immersing it in a rare earth salt solution to form a rare earth-containing bohmite layer. The feature of this technology is that it does not require the use of strong oxidants such as H2O2 and KMnO4 to shorten the disposal time, but the treatment temperature is higher.

5. Permanganate oxidation method

In general, permanganate is not only an excellent corrosion inhibitor for aluminum and alloys, but also accelerates corrosion. However, aluminum and alloys can be properly treated in KMnO4 solution to form an outstanding protective film. The technology comprises: immersing in sodium bromate, distilled water, Al(NO3)3-LiNO3 solution and KMnO4 solution, and the composition of the obtained film is Al2O3?MnO2. If the K2SiO3 solution is used again to close the pores of the oxide film, the effect is better. The protection of the KMnO4 oxide film is about 70% of the chromate film (synchronized by the salt spray test). For pure aluminum and aluminum alloys which are not very high in copper, zinc or iron, it can be treated in a potassium permanganate aqueous solution for 1 min to form a uniform yellow film near the chromate oxide film. For aluminum alloys with a higher tendency to corrode, in order to obtain a thicker protective film, it should be disposed of in boiling water or steam to form an oxidative worship, and then the film is closed twice or three times. Once closed in aluminum salt, once in KMnO4 solution, the oxide film function can be compared with chromate film, for aluminum alloy with high copper content and not coated, for best protection The film can be treated with a solution of 95-100 ° C potassium silicate solution for 1.5 min. Compared with the chromate film, the maximum strength of the film is that the drying temperature exceeds 65 ° C and the storage for a long time does not reduce its protection. . The potassium permanganate oxide film and the chromate oxide film have the same protective function against the fiber (fiber) corrosion of the paint film.

Keywords: aluminum alloy oxidation, imported aluminum alloy

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