At the bottom of the anodized aluminum film, one molecule of water is absorbed, but near the opening of the surface micropores, an estimated three molecules of water are absorbed. With the process of hydration, the chemical properties of the surface are improved, while the physical properties are reduced.

In order to maintain the above reaction, it is important to maintain the optimum pH value, and the use of buffer solution and filtration to remove suspended nickel compounds is an important strategy. According to the electron probe microanalysis of the cross section of the anodic oxide film, the strength distribution of nickel on the cross section can be observed that nickel mainly precipitates at the opening of the micropore.

Another solution for sealing holes with nickel salt at room temperature has also been developed successfully. The sealing effect of fluorine ion has been confirmed. CASS test shows that the sealing aluminum anodic oxide film has good performance. But the mechanism of this kind of hole sealing is not due to hydration, after long-term atmospheric exposure test, there is the possibility of electrolytic coloring film color.

Alkaline solution sealing treatment

The corrosion resistance of anodic oxide film of aluminum sulfate after sealing with alkaline solution has become the target of many researches.

The normal anodic oxidation film of aluminum sulfate with different thickness can be prepared, and the pH value of the sealing solution can be adjusted and controlled by inorganic acid or organic acid to seal the hole.

Its main conclusions are as follows:

(1) As the sealing solution becomes more alkaline, the corrosion resistance increases.

The cause is the neutralization of acids and bases in the micropores. Make the sealing effect better. Or aluminum anodized film and alkali chemical reaction generated boehm body film. Sometimes the surface changes are also found to be related to the pH value of the sealing solution.

(2) The market supply of professional production of nickel salt sealing solution performance is better.

(3) No difference was found in the sealing solution prepared with deionized water or tap water.

All the data in the table show some influence relationships, but no special provisions are made for the washing time after anodizing aluminum.

The alkaline solution sealing treatment can meet the requirements of alkali corrosion resistance stipulated in Jis standard.

Although it has been reported that the boehm body of aluminum anodized film has good chemical corrosion resistance, it is not clear how the boehm body sealed in alkaline solution is generated on the anodized film of aluminum sulfate. It has been reported that excessive hydroxide ions can hinder the formation of boehmite, while ammonia can promote the formation of boehmite.