| 摘要 |
A steel surface is coated with zinc by electro-plating, hot dipping or vapour deposition and the zinc coated with aluminium by vapour deposition, e.g. by an electron beam. The substrate is de-gassed by a high voltage discharge. Prior to the coating with zinc, the steel may be first coated with copper, gold, silver or brass e.g. by ionic deposition from aqueous medium or electro-plating. After applying the aluminium the surface may be chromated e.g. with K2Cr2O7 solution. In an example, steel panels are cleaned cathodically at 50 amps./sq.ft. in a solution of sodium carbonate and hydroxide and trisodium phosphate, pickled in muriatic acid, and then Zn plated in a bath (pH 3) of ZnSO4 and (NH4)2SO4 at 20 amps./sq.ft. |
