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. A method is provided wherein stabilization can be achieved by employing a combination of a) a hydroxybenzoic acid, preferably p-hydroxybenzoic acid; b) a hydrotropic sulphonic acid, preferably p-toluene sulphonic acid; and c) a hydrophobic alkaryl sulphonic acid, preferably dodecylbenzene sulphonic acid.

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 dissolution of metals such as iron, copper, or titanium. Stabilization can be achieved by employing a combination of a) hydroxybenzoic acid, preferably p-hydroxybenzoic acid; b) a hydrotropic sulphonic acid, preferably p-toluene sulphonic acid; and c) a hydrophobic alkaryl sulphonic acid, preferably dodecylbenzene sulphonic acid.

Abstract: Production of peroxomonosulphuric acid (Caro's acid) by reaction between concentrated hydrogen peroxide and sulphuric acid solutions can be impaired substantially when substoichiometric amounts of sulphuric acid are employed.The problem is ameliorated or removed by first forming a body of sulphuric acid-rich fluid (usually the smaller volume) and thereafter introducing into that body of fluid the hydrogen peroxide solution (usually the larger volume). The reaction mixture progressively becomes sulphuric acid-lean. The body of fluid is advantageously either concentrated sulphuric acid itself, or a premix formed by reaction between hydrogen peroxide and at least an equimolar amount of sulphuric acid. The process is particularly suitable for making Caro's acid when from 0.02 to 0.5 moles of sulphuric acid is employed per mole of hydrogen peroxide.

Abstract: It would be desirable to replace nitric acid based solutions for surface treating steels and like materials with a sulphuric acid based solution containing hydrogen peroxide, but such replacement solutions lose hydrogen peroxide rapidly through mainly iron-induced decomposition.A surface treatment solution that is based on sulphuric acid and hydrogen peroxide, but has improved stability, contains an effective amount in combination of hydrofluoric acid, are hydroxybenzoic acid and an N-alkoxyphenyl-acetamide. Preferably, the hydroxybenzoic acid is para-hydroxybenzoic acid and the N-alkoxyphenyl-acetamide is N-(4-ethoxyphenyl)-acetamide. It is preferable to employ a saturated solution of each of the two latter components, and this can achieved practically and simply by adding the solid components in the shape of a block or blocks which maintain the saturated solution over an extended period of time.

Abstract: Conventional plant to produce peroxomonosulphuric acid (Caro's acid) is large and emphasises extensive cooling, so that it is awkward to transport, can be cumbersome to install beside existing plant and can suffer from relatively expensive capital and/or running costs.In the present invention, Caro's acid is generated continuously in relatively small plant adiabatically, by introducing concentrated hydrogen peroxide into a stream of concentrated sulphuric acid in a reaction chamber dimensioned so that the throughput is very fast. In particularly suitable embodiments, the reaction chamber is annular at the points of introduction of the reagents, its width being greater in the vicinity of the hydrogen peroxide inlet than in the vicinity of the sulphuric acid inlet. The hydrogen peroxide inlet is preferably angled backwardly so that its encounter angle with the sulphuric acid stream is over 90.degree. to about 165.degree..

Abstract: Unless aqueous acidic hydrogen peroxide solutions are stabilized, an excessive rate of decomposition of hydrogen peroxide precludes their use for treatment of metal surfaces, such as of copper and copper alloys, during which use substantial concentrations of decomposition catalysts build-up in solution. Regular monitoring of the solutions for residual stabilizer content would demand sophisticated analytical equipment beyond the reach of many users.The invention provides a stabilizer in the form of a block of sparingly soluble material, whereby monitoring can be simply and readily effected visually or by a simple electrical or mechanical detection system. For copper/copper alloys preferred stabilizers are p-hydroxybenzoic acid and triphenyl carbinol.