| 摘要 |
PURPOSE:To form a uniform zincate film having superior adhesion when a zincate film is formed as an underlayer on an Al alloy plate by pretreatment before plating with a heavy metal, by adding specified metallic elements to the Al alloy. CONSTITUTION:When the surface of an Al alloy is plated with a heavy metal such as Cu, Ni, Cr or Sn, to the alloy are added 0.04-0.15wt% at least two kinds of elements which reduce cathodic polarization in an alkaline bath such as Cu, Zn, Ni and Mn. The surface of the resulting Al alloy is degreased, cleaned, and etched by immersion in an aqueous NaOH soln. having 10% concn. at 70 deg.C for 30sec. The etched surface is washed neutralized with an acid, and treated with an aqueous soln. contg. ZnO and NaOH for 1min to form a uniform zincate film having superior adhesion on the etched surface. The surface of the Al alloy coated with the zincate film is electroplated with a heavy metal such as Cu, Ni, Cr or Sn according to the purpose for which the alloy is used.
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