Poster De Conférence Année : 2016

Effect of the carbon content and of the hardened state on the corrosion behaviour of cast carbon steels in an acidic aqueous milieu. Part1: Study of the possible carbon content influence on the obtaining conditions and on the stability of the passive state

Résumé

Carbon steels are among the cheapest metallic materials able to serve as structural materials. Initially issued fr om the reduction of ferrous ore in blast furnace they may be submitted to incomplete or total decarburization and removing of silicon, by treatment of the obtained cast iron in blast furnace or after in a converter. From the m olten state their solidification leads to various microstructures depending on their final carbon c ontent: wholly ferritic (no remaining carbon), ferritic-pearlitic (carbon existing, with content lower than 0.8 wt.%), pearlitic (carbon close to 0.8 wt.%) or hyper-eutectoid (higher than 0.8 wt.%). In contrast with their chromium-containing versions such Fe-C are easily threatened by corrosion, especially in acidic milieu. However this degradation ma y be limited by cathodic polarization by applying a low potential carrying them in their immunity domain. This energy costly technique can be replaced by a nodic polarization since it is possible for iron to be mainta ined in its passive state, even in acidic solutions, with lower electrical energy cons umption than for the cathodic polarization. In order to precise some operating parameters it is necessary to know the behaviour in passivation of the steels considered to protect. In this work the focus is done on the possible variability of the passivation behaviour of cast steels versus the car bon amount they contain. A series of binary Fe-C steels was elaborated by classical foundry with carbon contents dispersed over the whole possible range of carbon weight content [0 ; 2 wt.%]. These steels were mounted as electrodes and submitted to a cyclic polarization (anodic ↔ cathodic) in order to better know the dependence of the obtaining conditions and the of the stability of the passive state, on the carbon content of steels issued from such an elaboration route. Thus all the studied carbon steels get passivated by anodic polarization, passivation state that they can keep if the potential is maintained at a level high enough. There was obviously no dependence of the conditions of passivation and of passivation keeping on the carbon content. If in the passivation state the anodic current density is unsurprisingly lower than in the active state but not much lower. Additional tests may be required to verify the sustainability on long time of the passive state with constant polarization at fixed potential. The tendency to have transpassivation phenomenon delayed to higher potential when the carbon content on the steel increases remains to be verified and explained. These results concerning only cast carbon steels, the case of plastically deformed carbon steels remains to be examined since many steels are hardened by cold or hot rolling before use. This is the purpose of the second party of this work.

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hal-03283828 , version 1 (12-07-2021)

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  • HAL Id : hal-03283828 , version 1

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Manale Belhabib, Patrice Berthod. Effect of the carbon content and of the hardened state on the corrosion behaviour of cast carbon steels in an acidic aqueous milieu. Part1: Study of the possible carbon content influence on the obtaining conditions and on the stability of the passive state. Eurocorr 2016, Sep 2016, Montpellier, France. ⟨hal-03283828⟩
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