| abstract |
A phosphating process for aluminium surfaces employs an aqueous acidic solution containing 0.8-1.5 g/l zinc, 5-40 g/l phosphate, 50-2000 mg/l iron(II), 20-800 mg/l tungstate, 0.5-2.5 g/l fluoride and/or complexed fluoride, 0.2-5 (preferably 0.4-1) g/l hydroxylamine (derivative), 1-8 g/l nitrate and optionally up to 2.5 g/l manganese, magnesium, calcium, copper, cobalt, strontium, vanadium and/or nickel. Also claimed is a phosphating medium having the above composition, the iron(II) content preferably being 200-500 mg/l. |