Significance of Coplanar Macrocells to Corrosion in Concrete-Embedded Steel

Abstract The influence of microcells and galvanic macrocells on the corrosion kinetics of concrete-embedded steel was investigated experimentally. Nine stainless steel/carbon steel coplanar macrocouples in cathodic-to-anodic ratios of 0.02 to 50 were cast in concrete slabs made from cement, sand, and water in a 1:3:0.5 proportion plus 2% calcium chloride (CaCl2 per cement weight. Corrosion potential (Ecorr), galvanic current (ig), polarization resistance (Rp), and impedance measurements from 100 kHz to 0.01 Hz were made for the two metals, coupled and uncoupled. ig data provided by a zero resistance ammeter led to potentially underestimated corrosion rates for anodic areas, whereas Rp measurements provided fairly reliable corrosion rates. Macrocells polarized anodic areas very slightly at points where an anodic and a cathodic process took place simultaneously.