Ugine, Aciers De Chatillon Et Gueugnon

Ugine Sa

Dominique Henriet

Paul Didier

Didier Paul

Laurent Prost

The invention relates to a process for pickling stainless steel products, in which the pickling bath used has as its initial composition, HF.gtoreq.10 g/l, dissolved ferric iron (Fe.sup.3+).gtoreq.15 g/l, and water=balance. During the pickling operation(s), the redox potential of the bath is monitored and maintained between +100 mV and +350 mV by oxidation of the bath, if necessary, by at least one or several addition(s) of oxidant to the bath. The process of the invention applies particularly to the industrial pickling of stainless steel sheets and strips, in which it is possible to avoid the use of nitric acid and the resulting pollution.

Process for the acid pickling of stainless steel products

Pickling process in an acid bath containing an oxidant in order to enhance the pickling kinetics, wherein at least one peroxygenated derivative of titanium or at least of one element of the titanium family included in the product to be pickled is formed, the metal being ionized to a higher valency, the formation of the peroxygenated compound is controlled by measurement of the redox potential, and the quantity of oxidizing agent is limited so as to maintain an oxido-reduction potential lower than the passivation potential of the metallic product.

Pickling process in an acid bath of metallic products containing

A method for pickling steel materials, in particular continuously on a treatment line, comprising a shot-blasting operation, a preparation operation, a pickling operation and a passivation operation, in which line the preparation operation is carried out by bringing the materials into contact with at least one 2 to 10N sulphuric acid solution, and in which line the pickling operation is carried out by bringing the materials into contact with at least one solution containing 1 to 10% by weight of hydrofluoric acid and Fe.sup.2+ and Fe.sup.3+ ions. No figure.

Method for continuous pickling of steel materials on a treatment line

Method for pickling or cleaning materials of steel, in particular stainless steel, comprising treating the materials with an aqueous solution containing ferrous ions and ferric ions and an organic acid which does not oxidize the iron in an amount sufficient to maintain the Fe.sup.2+ and Fe.sup.3+ ions in solution, the ferric and ferrous ions being present in the solution in a ration Fe.sup.2+ /Fe.sup.3+ between 10/90 and 40/60, and maintaining the ration Fe.sup.2+ /Fe.sup.3+ within the defined range by addition of hydrogen peroxide.

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Chambourcy, France

Dominique Henriet