Process for the acid pickling of stainless steel products
AssigneeUgine, Aciers de Chatillon et Gueugnon
InventorDominique Henriet
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Abstract
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.
Claims21
A process for pickling a stainless steel product, comprising:
- providing a pickling bath having a redox potential and consisting essentially of (i) HF in an amount of from 60 grams per liter to 150 grams per liter, (ii) dissolved Fe.sup.3+ ions as the pickling agent, (iii) at least one oxidizing agent selected from the group consisting of ozone, chlorine, water vapor, alkaline earth and alkaline metal permanganates, peroxyurea, percarbonic acid, perboric acid, perbenzoic acid, persulfuric acid, perphosphoric acid, periodic acid, perphthalic acid, sodium precarbonate and magnesium percarbonate, and (iv) water;
- and
- inserting said stainless steel product into said pickling bath wherein, during the pickling operation, the redox potential of said bath is monitored and maintained between about +100 mV and about +350 mV.
Dependencies are inferred from the claim text.