2008 Volume 57 Issue 10 Pages 449-454
Severe localized corrosion of steel pipes buried in concrete/soil systems (known as macro-cell corrosion) is induced by cathodic reactions on those steel surfaces that are located in the concrete, accompanied by anodic reactions (i.e., corrosion) on those surfaces that are located in the soil. The addition of cathodic inhibitors to the concrete in the form of concrete admixtures is therefore expected to be an effective means of suppressing this phenomenon. Uric acid, NTMP, and 5-aminouracil were selected as candidate materials for the cathodic inhibitors, and were appended to concrete test pieces (water/cement ratio : 61%). Measurements of the currents flowing between steel (SGP) pipe test specimens embedded in concrete test pieces and pipes buried in soil (electrically connected to the steel pipe test specimens in the concrete) were performed in order to evaluate the inhibitory effects over a period of 116 days. The currents were decreased by the addition of uric acid (dry mixed in a ratio of 1 : 10 by weight with ordinary Portland cement), which shows that macro-cell corrosion can be effectively controlled by uric acid. The other compounds were not effective.
