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US 5,154,774 AGranted
Process for acid pickling of stainless steel products
AssigneeUgine, Aciers de Chatillon et Gueugnon
InventorsBernard Bousquet, Bernard Chetreff
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AssigneeUgine, Aciers de Chatillon et Gueugnon
InventorsBernard Bousquet, Bernard Chetreff
Estimating the term…
The invention relates to a process for pickling stainless steel products, in which a pickling bath is used having the initial composition: HF 10 to 50 g/l Dissolved ferric iron (Fe.sup.3+).gtoreq.15 g/l Water: as required at a temperature of between 15.degree. and 70.degree. C., characterized in that, during the pickling operation(s), the ferric iron content of the bath is maintained at at least 15 g/l by oxidation of the bath comprising at least one or several injections of air in a total quantity greater than or equal to 1 Nm.sup.3 per m.sup.2 of pickled stainless steel and per hour of pickling of each unit of surface area pickled. 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.
A process for pickling a stainless steel product, in which the pickling bath used has a composition consisting essentially of HF present in an amount of from 10 to 50 g/l, dissolved Fe.sup.3+ ions present in an amount of at least 15 g/l, and water as the remainder, wherein said Fe.sup.3+ ions originate from ferric fluoride so that said bath contains only F as acid radicals, wherein said process is carried out at a pickling bath temperature of between 15.degree. and 70.degree. C. and wherein, during the pickling operation, air is injected into said bath in a total amount greater than or equal to 1 Nm.sup.3 per m.sup.2 of stainless steel pickled per hour, wherein further, the redox potential of said bath is maintained between +100 mV and +300 mV by adjusting, if necessary, the oxidation state of said bath by intermittent addition of an additional oxidizing agent, maintaining consequently the Fe.sup.3+ ion content in said bath to at least 15 g/l, and obtaining a soluble sludge.
A process for pickling a stainless steel product, in which the pickling bath used has a composition consisting essentially of HF, dissolved Fe.sup.3+ ions, and water as the remainder, wherein said Fe.sup.3+ ions originate from ferric fluoride so that said bath contains only F as acid radicals, wherein, during the pickling operation, air is injected into said bath in a total amount greater than or equal to 1 Nm.sup.3 per m.sup.2 of stainless steel pickled per hour, wherein further, the redox potential of said bath is maintained between +100 mV and +300 mV by adjusting, if necessary, the oxidation state of said bath by intermittent addition of an additional oxidizing agent, maintaining consequently the Fe.sup.3+ ion content in said bath to at least 15 g/l, and obtaining a soluble sludge.
Dependencies are inferred from the claim text.