Corrosion d’alliages à transition actif-passif en eau de mer

C.N.R. Istituto per la Corrosione Marina dei Metalli Genova, Italy

Abstract

The settlement of a bacterial aerobic biofilm on the surfaces of a lot of active-passive alloys (stainless steels, Ni-Cu alloys, Ni-Cr alloys, titanium...) immersed in natural seawater, causes a depolarization of oxygen reduction. From that it follows:

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  an increase of 300-40 mV of the free corrosion potential of alloys in passive state and, therefore, an increase of the risk of localized corrosion initiation ;

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  an increase, up to two orders of magnitude, of the localized corrosion rate;

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  an increase of the galvanic currents in the coupling of active-passive alloys with other less nobles ones.