GB1445553A - Process for producing an adherent metal coating on an article - Google Patents

Abstract

1445553 Cleaning Al Mg; electroless- or electro-plating REDERIAKTIEBOLAGET NORDSTJERNAN 21 March 1975 [22 March 1974] 11926/75 Headings C7B C7E and C7F An article of Al, Mg, Al- or Mgbased alloy is treated in a solution containing (1) HF, HBr or HI (2) an acid different from (1) and selected from HC1, HBr, HF, HI, H 3 PO 4 , CrO 3 , HClO 4 and H 2 SO 4 and (3) a soluble metal salt, and is then coated with metal. The metal of said salt is level with, or below, Mg in the electro-motive series, e.g. Ni, Cr, Fe, Co, Mn, Mg or Zn. Amounts of the ingredients may be (1) 0À1-10 wt. per cent (2) 0À05-20% and (3) 0À5-50%; water constitutes the balance; the pH may be < 2.5 and treatment is for < 1 min at room temperature. The metal coating may be applied by electrolysis, electrolessly, by spraying, or chemical or vacuum vapour deposition, and may be Ni, Co, Fe, Ag, Cu, Cr, Sn, Pb or In; Cr may be electro-plated at 50‹C and 50 A/dm<SP>2</SP> from a bath of 250 g/l CrO 3 and 2.5 g/l H 2 SO 4 ; Ni may be electro-plated at 25-70‹C, pH 3À5-4À5 and 2-14 A/dm<SP>2</SP> from a bath of 300 g/l Ni sulphamate, 30 g/l Ni Cl 2 .6H 2 O and 30 g/l H 3 BO 3 ; an electroless Ni bath contains Ni Cl 2 , NaH 2 PO 2 , NH 4 Cl and NH 4 citrate, and an electroless Co bath contains CoCl 2 , NaH 2 PO 2 , NH 4 Cl and Na citrate; the coated article may be heated to >200‹C,