．Pretreatment of alloy aluminum cylinder for plating

　 It is no question about the importance of alloy aluminum cylinder,
which will be developed and applied. However, the physical and chemical features
of alloy aluminum are much difficult for plating compared to normal steel substrates,
especially the pretreatment for plating.

    ■ Aluminum is a typical amphoteric metal. The tolerance in acid or alkali liquid is low.
    　 The over corrosion on the substrate should be prevented. The aluminum substrate
    　 should not be loose to scale off, affecting the combination condition between
    　 plating layer and alloy aluminum.

    ■ The chemical feature of aluminum is very agile. It is easy to be oxidized and should
    　 be prevent the oxidized film quickly formed after the oxidized film is eliminated in
    　 acid or alkali.

  • ■ The silicon additives in aluminum alloy cylinder increase the difficulty of processing.
    　 The silicon on the coated surface should be removed.