(1) Classification of industrial aluminum sealing process:

  Industrial aluminum anodized film has a porous layer structure, strong adsorption capacity and chemical activity, especially in a corrosive environment, the corrosion medium can easily penetrate the membrane hole and cause matrix corrosion. Therefore, the anodized film needs to undergo a sealing treatment regardless of coloring, so as to improve the resistance of the oxide film to corrosion, insulation, and abrasion, and to weaken its adsorption to impurities or oil.

  Oxide membrane sealing method is many, there are hot water sealing method, steam sealing method, salt solution sealing method and organic coating sealing method. Here are three frequently used high temperature sealing, cold sealing and medium temperature sealing.

Industrial aluminum high temperature hydration sealing process:

A hydration sealing principle

  The anodized film of industrial aluminum has two forms of reaction in water: one is in water below 80°C and the PH is less than 4 and it is combined with water into Bayer alumina trihydrate. This combination is only physical combination. It is reversible. The other is the synthesis of boehmite-type monohydrated alumina with alumina and hydration in neutral water above 80°C. This is the reaction process commonly referred to as hydration sealing.

  Since the density of monohydrated alumina (3014 kg/m3) is smaller than that of alumina (3420 kg/m3), the volume after the reaction increases by about 33%, blocking the pores of the oxide film.

  High temperature hydration seals include boiling water seals and atmospheric pressure, pressurized steam seals. The corrosion resistance and corrosion resistance of the oxide film treated by the steam sealing hole are related to the steam pressure and the sealing time. Generally, as the pressure increases, the time is prolonged, the corrosion resistance is improved, and the corrosion resistance is reduced.

Industrial aluminum high temperature sealing process and influencing factors:

  Boiling water sealing hole and steam sealing hole process are shown in Table 3-41.

  The sealing effect of steam (atmospheric pressure and pressure) is better than that of sealing with boiling water. High-pressure vessels or special steamers are required, and the cost is high. Therefore, steam sealing holes, especially pressurized steam sealing holes, can only be used for the processing of small industrial aluminum profiles.