Galvanic currents and corrosion rates of reinforcements measured in cells simulating different pitting areas caused by chloride attack in sodium hydroxide

Chlorides induce localized corrosion in the reinforcement. The pits formed a substantial reduction in the cross-sectional area. The smaller is the ratio between the size of the corrosion spot and the surrounding passive metal area acting as cathode, the higher is the corrosion rate or the progression in the pit depth. This, however, is not always the case. To understand well the macro or microcell behavior of the corrosion of reinforcements, this paper reports a study on the effect of decreasing sizes of anodic zones until relatively small, maintaining the size of the cathode constant. In addition, to enhance the pure anodic behavior of the corroding zone, an acidic solution was used as an anolyte. Measuring the galvanic current (Ig) and the corrosion rate (Icorr) by using zero resistance ammeter (ZRA) and polarization resistance (Rp) techniques, respectively, was crucial to differentiate the microcell contribution from that of the macrocell. The results indicate that while Ig increased as the anodic area decreased, Icorr presented a maximum for the area ratios, SA/SC = 1/3.