1, the aluminum alloy immersed in boiling water, aluminum oxide film thickening of natural will continue, and finally reached 0.7 ¡« 2 ¦Ì M. Oxide colourless or milky white, the water film is gamma boehmite alumina, its structure is compact, pH in 3.5 ~ 9 between the film is very stable, can be used as bottom paint. Superheated steam more than 100 ¡æ to form the membrane, the actual process is 75120 ¡æ water treatment in a few minutes. In order to improve the film thickness, adding ammonia or Triethanolamine in pure water, can be a porous oxide film. Add ammonia treated film color is white, uniform color. The paternity of ammonia added within the range of 0.3% ¡« 0.5%
2, zirconium salt oxidation
Zirconium containing solution instead of chromate pretreatment for aluminum substrate surface has been accepted by people, especially suitable for chemical coating of aluminum alloy parts before the conversion coating treatment, can increase the binding force of the coating and the substrate, improving the corrosion resistance, while the film itself has a certain ability of anti corrosion.
3 titanium salt oxidation
Titanium and chromium is very similar, no corrosion in almost all the natural environment. The corrosion resistance of the excellent source in continuous and stable, in the oxide film formed on the surface of the combined firm and has protective properties. High reactivity of titanium and oxygen affinity and strong so that the metal surface is exposed to air or moisture in the environment can be formed immediately film. In fact, as the chromate film, as long as the oxygen or water micro environment (tidal) exist, because the titanium and oxygen strong affinity, titanium oxide film destroyed can self repair immediately.
4 rare earth metal salts oxidation
Rare earth metal salt chemical oxidation will replace chromate film, material can be by impregnation treatment, treatment solution generally require heating to produce a protective layer on the surface of the parent metal. Its corrosion resistance is provided by the formation of rare earth oxide on the metal surface of worship. The aluminum alloy of rare earth processing technology with the mixed solution of rare earth metal salt, oxidizing agent, film forming promoter, Pu auxiliary film forming agent composed of processing method. Rare earth salt mainly refers to the cerium salt such as CeCl3, Ce (NO3) 3, Ce (SO4) 2, (NH4) 2Ce (NO3) 6, film forming promoter NaOH, HF, SrCl2, (NH4) 2ZrF, H2O2, KMnO4, oxidant (NH4) 2S2O8. Treatment process without oxidant in processing solution with rare earth bohmite layer technology. This technology is that the aluminum alloy with hot water is formed on the surface of bohmite layer, and then dipped into the rare earth salt solution, the formation of bohmite layer containing rare earth. The characteristics of this process is not required to use H2O2, KMnO4 and other strong oxidizing agent to shorten the treatment time, but the high temperature treatment.
5 potassium permanganate oxidation
In general, permanganate on aluminum and alloy is not only a good corrosion inhibitor, but also accelerated corrosion. But the aluminum and aluminum alloy in KMnO4 solution after proper treatment can form protective film good. Its process includes: continuous in sodium bromate, distilled water, Al (NO3) immersed in 3-LiNO3 solution and KMnO4 solution, the composition of the film is Al2O3 ¡¤ MnO2. If you use the K2SiO3 solution pores closed oxide film, a better effect. Protective KMnO4 film is about the chromate film 70% (over the same period in salt spray test). On the pure aluminum and copper, zinc or iron is not very high aluminum alloy, in Potassium Permanganate aqueous solution 1min can form uniform yellow film was similar with the chromate film. The aluminum alloy has a higher corrosion protective film, thicker, should first treatment in boiling water or steam, to form oxidation worship, and then on this film for two times or three times closed treatment. A is closed in the aluminum salt, one was closed in KMnO4 solution, the properties of the oxide film formed in this way can be compared with the chromate film, for containing high copper, aluminum alloy without coating, protective film for the best, can be coupled with the process of a 95 ~ 100 ¡æ potassium silicate solution 1.5min, compared with the chromate film, this film is the biggest advantage of drying temperature over 65 ¡æ and long-term storage will not reduce its protective. Potassium Permanganate oxide film and chromate film on the film wire (Xian Wei) protective properties of the nodular corrosion of exactly the same.