ZINC COATED STEEL PLATES COATED WITH A PRE-LUBRICATING HYDROXYSULPHATE LAYER AND METHODS FOR OBTAINING SAME

摘要

The invention concerns a steel plate coated with a metal layer based on zinc and a zinc hydroxysulphate layer, whereof the surface density of sulphur is more than 0.5 mg/m<2>. The invention also concerns a method for obtaining said plate by treating a zinc coated sheet metal: either in a highly alkaline sulphate solution under polarisation: or in a sulphate solution containing Zn<2+> ions without polarisation. The hydroxysulphate deposit brings about a pre-lubricating effect applicable to operations for forming sheet metal.