Acciai Speciali Terni, S.p.a.

Henkel Kommanditgesellschaft Auf Aktien

Franco Mancia

Sandro Fortunati

Augusto Musso

Paolo Giordani

Stefano Trasatti

Yoannis Demertzis

A process for electrolytic pickling of stainless steel of the ferritic, martensitic, austenitic and duplex series as well as superaustenitic and superferritic steels, nickel or Ni/Cr-based super alloys, and titanium and its alloys is provided. The process utilizes an electrolytic pickling solution containing H SO in a concentration of from 20 to 140 g/l and Fe ions in a concentration of from 15 to 80 g/l, the Fe ions being present a quantity corresponding to a Fe /Fe ratio of >1 and preferably >3.

Process for electrolytic pickling using nitric acid-free solutions

Method for pickling products made of steel, characterized in that within the pickling bath Fe is present, directly added in a controlled concentration, or produced in the pickling bath itself by adding an oxidizing agent such as hydrogen peroxide, ozone, permanganates. persulphates and oxygen.

Method for pickling steel products

A method for pickling products in a metal alloy containing iron, and products in titanium and alloys thereof, in the absence of nitric acid as an oxidizing agent, and for the recovery of the exhausted solutions, characterized in that the recovery of the exhausted solutions deriving from pickling comprises the following steps: sending of the pickling solution, both as catholyte and as anolyte, in an electro-chemical cell optionally of the membrane type to separate the Fe,(or Ti,) ions to be disposed of, from the Fe,(or of the Ti,and Ti,) ions to be recovered, obtained by reduction at the cathode of the Fe,ions which are in the catholyte to Fe,(or of the Ti,and Ti,ions to Ti,) and of oxidation at the anode Fe,(or Ti,) ions which are in the anolyte to Fe,(to Ti,and Ti,); treating the catholytic solution coming out of the cell and enriched in Fe,(or Ti,) ions as to allow the separation in two phases, a first phase containing the metal canions Fe,, Cr,, Ni,(or Ti,) to be disposed of and a second liquid phase deprived of said metal cations to be sent in the pickling bath; and sending the anolytic solution, coming out of the cell and enriched in Fe,ions (or Ti,or Ti,&plus;), in the pickling bath. It is also the object of the present invention an apparatus thereof.

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Rome, Italy

Franco Mancia