Mild steel passivation and depassivation in simulated concrete pore solution containing bacteria metabolites

Reinforced concrete structures are subject to intense deterioration when exposed to a microbial environment. Metabolic products of bacteria involved in the sulfur cycle seems to be the main responsible of the cement matrix deterioration, while their effects on the reinforcing bars corrosion are still largely unknown. Ca(OH)<inf>2</inf><inf>sat</inf> solution was used to simulate the alkaline environment of sound concrete, the growth of the protective oxide layer was investigated through several electrochemical techniques. Anodic polarizations in Na<inf>2</inf>S and H<inf>2</inf>SO<inf>4</inf>, simulating bacteria metabolites, allowed to study the depassivation mechanism highlighting a competitive adsorption with the oxide layer in the first case and intense generalized corrosion in the latter.