Aluminium anode: dc power supply is used in normal nickel plating, the plating solution is generally maintained at pH 4.2-4.5, with boric acid buffer solution, often with other buffering agents added.

This electroplating solution should not be used as an electrolytic coloring solution for anodized aluminum film, because the above mentioned problem of film stripping will occur during direct current electrolysis in micropores. In order to prevent the stripping of anodized aluminum film, it is necessary to restrain the discharge condition of hydrogen ion, so that the migration of nickel ion is dominant, so only low concentration of acid or salt is used.

With the exception of nickel salts, boric acid is the main ingredient, and other buffering agents are kept as low as possible.

When the conductivity is used as a method of monitoring the bath fluid, the conductivity of the added buffer is not allowed to exceed 10% of the conductivity of the metal salt

Due to the high porosity of anodized aluminum film, it is easy to adsorb sulfuric acid, dissolved aluminum salts and other components dissolved in the bath solution. This adsorbed substance is often the cause of coloring failure. Maintaining a certain amount of this acid in the micropore will promote the stripping of the oxide film. This acid diffuses from the micropores into the coloring solution and contaminates the coloring solution. So thorough washing is very necessary. Twice-running water washing is a very effective method of washing, despite the increased water use. Electrolysis and neutralization treatment is also a method, the stirring of cleaning water has little effect on the liquid absorbed in the micropores. The main process of removing liquid from micropores is diffusion. In order to accelerate the diffusion, increasing the temperature of the cleaning water is an effective idea, and the acidity of the cleaning tank should be kept as low as possible.

During electrolytic coloring, metal ions are consumed and sulfate concentration is increased. In some cases, the sodium concentration sometimes increases. In order to prevent sodium ions from increasing to unacceptable concentrations, sodium ions should be removed continuously or regularly. The use of basic anion exchange resins is the method of removing foreign impurities.