Effect of impurities in electrolytic solution
The degree of coloration of aluminum profiles depends largely on the quality of the oxide film. Therefore, in the anodizing solution of sulfuric acid, the influence of impurities on the oxide film can not be ignored. The impurities are mainly metal ions such as copper, iron, aluminum and organic impurity pollutants, which should be removed in time to maintain the normal use range of the solution.
(1) The copper ions are displaced and deposited on the surface of the aluminum member, causing the oxide film to loosen and lowering the transparency, corrosion resistance and electrical insulation properties. Therefore, the copper ion content is not allowed to exceed 0.02 g/L.
(2) The chloride ion is from the tap water or the cooling water after the cooling tube is broken. The chloride ion content should be less than 0.2g/L. Otherwise, the oxide film formed is rough and loose, and the surface of the aluminum part is etched (breakdown).
(3) The aluminum ion in the aluminum ion electrolyte is gradually increased. When the content is more than 25 g/L, the conductivity of the electrolyte decreases, and the anodized surface of the aluminum alloy profile exhibits white spots or blocky white spots, and the film layer is formed. The adsorption capacity is lowered and the dyeing is difficult.
(4) Iron ions in the iron ion electrolyte are not allowed to exceed 0.2 g/L, otherwise dark streaks may appear.
(5) Organic impurities hinder the formation of an oxide film, and after the film adsorbs oil stains, the coloration is uneven and streaks appear.