Solvay Interox Gmbh

Solvay (Societe Anonyme)

Solvay

Sarah J Colgan

Neil J Sanders

Colin F McDonogh

Process for pickling a metal using hydrogen peroxide

In the invention pickling process, steel and nickel or chromium alloys are pickled with an acidic pickling solution employing an oxidant, particularly hydrogen peroxide, and in which liquor is recirculated through inlets comprising a nozzle feeding liquor into a diffuser such that liquor is withdrawn from the bath and the volume of liquor flowing through the diffuser is a multiple of flow through the nozzle. Steel or the alloys are pickled with an acidic solution containing iron and free hydrogen peroxide at a concentration of up to 0.1 gpl. The process can operate effectively at a free fluoride concentration of from 20 to 30 gpl and a sulphuric acid concentration of from 80 to 110 gpl. The lifetime of the bath before it needs to be replaced can be lengthened by the process compared with using an air agitation system.

Pickling process

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.

Process for treating a metal surface with an acidic solution containing hydrogen peroxide and a stabilizer

Metal surface treatment solutions and process

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Warrington, United Kingdom

Sarah J Colgan