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Surface Cr-depletion beneath the oxide scale in heat-treated stainless steels plays a determining role in both functions of acid pickling which are:(i) scale detachment or descaling proper and (ii) restoration at the metal surface of the base Cr content, i.e. of the highest passivity properties. As the * Electrochemical Society Active Member.

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Potentiostatic pickling in 20~ aqueous HzSO 4 was investigated on hot-and cold-rolled strips of stainless steels from industrial lines, in order to assess the potentiality of this technique. Experimental evidences for AISI Types 202, 304, 316, 410 and 430 are given. Optimum pickling conditions were defined on the basis of the potentiodynamic behaviour of oxidized specimens.Visual and electrochemical evaluation of pickled surfaces showed that:(i) The potentiostatic technique makes descaling and pickling of stainless steels quite feasible in sulphuric baths; (ii) remarkable advantages result over ordinary chemical treatments in terms of speed of scale removal; (iii) a higher efficiency of restoration of passivity properties also results.

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