| abstract |
Aqueous acidic solutions of hydrogen peroxide used for metal surface treatments suffer from an increased decomposition rate of the hydrogen peroxide, caused by the dissolved metals such as iron, copper or titanium. Stabilisation can be achieved by employing a combination of a) a hydroxybenzoic acid, preferably p-hydroxy benzoic acid, b) a hydrotropic sulphonic acid, preferably p-toluene sulphonic acid and c) a hydrophobic alkaryl sulphonic acid, preferably dodecylbenzene sulphonic acid in a weight ratio of a) : b) : c) of 80-200, 50-120 and 2.5-6. Most desirably, the stabiliser is present at a concentration of 3-10 g/l in 35-70 % hydrogen peroxide solution introduced into the aqueous acidic metal treatment solution. |