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Study of Two Factors Possibly Influencing the Obtaining Conditions and the Stability of the Passive State of Cast Carbon Steels in Acidic Aqueous milieu. Part 2: Hardened State

Manale Belhabib, Patrice Berthod

In this second part of the work carried out about the conditions of passivation and of stability of this state for carbon steel, this is the possible influence of a preliminary plastic deformation, issued from cold rolling or from stress existing during service, which was examined. Parts of the same Fe-xC steels, with x=0, 0.4, 0.8, 1.2 and 1.6 (weight percents) as studied in their as-cast states in the first part, were compressed until reaching significant amount of plastic deformation. The resulting hardened steels were mounted as electrodes and subjected to cyclic polarization in molar sulphuric solution. As for the as-cast state, all the samples were able to get passive for polarization at potential high enough, and fall again in the active state when potential is decreased under a critical value. The conditions of obtaining the passive state as well as to maintain it were noted. The current density of corrosion in the passive state is low but it tends to be higher than for the not deformed alloys.