RELATIONSHIP BETWEEN BACTERIAL-COLONIZATION AND CATHODIC CURRENT-DENSITY ASSOCIATED WITH MILD-STEEL SURFACES

Cathodic protection (CP) is an effective way to control corrosion of m arine structures. In addition to the inorganic film formed during cath odic polarization, microorganisms can become firmly attached to the su rfaces and interfere with the cathodic process. In the present experim ents the role of two eubacteria was examined in mono and coculture in the formation of the calcareous him under CP in both galvanostatic and potentiostatic mode, The presence of a biofilm interacted with the sc ale deposition process, which fed to a significant increase in the cat hodic current demand. This increase was effected by two phenomena, viz . the decrease of local pH due to bacterial fermentation products and the oxidation of cathodically-produced hydrogen by the sulphate-reduci ng bacteria. In addition, the study of a preexisting biofilm placed un der CP led to the same conclusions.