GALVANIZED ALUMINIUM SHEET

摘要

PCT No. PCT/EP97/02329 Sec. 371 Date Apr. 8, 1999 Sec. 102(e) Date Apr. 8, 1999 PCT Filed May 7, 1997 PCT Pub. No. WO97/43467 PCT Pub. Date Nov. 20, 1997A method for applying a zinc layer onto an aluminum or aluminum alloy sheet, comprising pretreating the surface and applying the layer by electrolytic galvanizing, the pretreating comprises electrochemical graining of the surface, for example in a solution having a pH less than 3 with an alternating current applied between the sheet and an electrode. In an alternative method, the pretreating includes applying a preliminary zinc layer by immersing the surface in a zinc-containing alkaline solution, applying a potential to the sheet and reversing the polarity of said potential at least once. The sheets are useful for building cladding sheets and automotive panels.