PROCESS FOR PICKLING AND/OR PASSIVATING A STAINLESS STEEL

The present invention relates to a process for pickling and/or passivating a stainless steel with acid aqueous treatment solutions comprising FeIII ions and FeII ions, wherein at least a first and a second treatment solution are used in sequence, wherein: the redox potential of the second solution i...

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Bibliographische Detailangaben
Hauptverfasser:	ASTENGO, Giovanni, MARTINES, Stefano
Format:	Patent
Sprache:	eng ; fre ; ger
Schlagworte:	CHEMICAL SURFACE TREATMENT CHEMISTRY CLEANING OR DEGREASING OF METALLIC MATERIAL BY CHEMICALMETHODS OTHER THAN ELECTROLYSIS COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL COATING MATERIAL WITH METALLIC MATERIAL COATING METALLIC MATERIAL DIFFUSION TREATMENT OF METALLIC MATERIAL INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL METALLURGY SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION
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Beschreibung
Zusammenfassung:	The present invention relates to a process for pickling and/or passivating a stainless steel with acid aqueous treatment solutions comprising FeIII ions and FeII ions, wherein at least a first and a second treatment solution are used in sequence, wherein: the redox potential of the second solution is maintained at a value higher than the redox potential of the first solution; the total concentration of iron ions in the first treatment solution is maintained at a value higher than the total concentration of iron ions in the second treatment solution; the first solution, when exhausted, is subjected to regeneration to obtain regenerated acid, which is recycled to the second solution; part of the second solution is transferred to the first solution to compensate for the removal of the first exhausted solution.