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Henkel Kommanditgesellschaft Auf Aktien

Henkel Kommanditgesellschaft Auf Aktien (henkel Kgaa)

Dario Negri

Paolo Giordani

Mauro Rigamonti

Valentino Gasparetto

A process for pickling martensitic or ferritic stainless steel, preferably in the form of wires, tubes or rods, wherein the stainless steel is placed in contact with a pickling solution which has a temperature in the range 15 to 29&#xb0; C. and contains 50 to 120 g/l of free sulfuric acid, 5 to 40 g/l of free HF and 5 to 40 g/l of Fe(III) ions. Such pickling may be incorporated into a sequential process, wherein the stainless steel is a) subjected to a treatment during which the oxidic coating is applied, preferably sand-blasting or metal-blasting, treatment with a molten salt or treatment with an aqueous permanganate/alkali metal hydroxide solution, b) pickled in accordance with the aforedescribed process, and c) post-treated with a passivating solution.

Process for pickling martensitic or ferritic stainless steel

A chromium- and nitrogen-free brightening and passivating treatment for metal surfaces, particularly iron and steel, comprises: at least one acid; at least one substance containing a peroxy moiety; and at least one organic substance selected from the group consisting of; molecules that contain both at least one ether moiety and at least one hydroxyl moiety; molecules that contain at least two ether moieties; and molecules that contain in each molecule both at least one ether moiety and one nitrogen atom that is covalently bonded to at least three carbon atoms. Preferably part of the acid contains phosphorus, which has been found to act synergistically with the organic substance to stabilize peroxy compounds against decomposition, particularly in the presence of metal ions.

Brightening/passivating metal surfaces without hazard from emissions of oxides of nitrogen

Process for pickling stainless steel in the absence of nitric acid and in the presence of chloride ions

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Bagnolo Cremasco, Italy

Dario Negri