Corrosion products of reinforcement in concrete in marine and industrial environments

Abstract

The corrosion products formed on embedded steel in concrete under simulated marine and industrial conditions and natural marine environment were studied. A 0.50 water/cement ratio concrete was used concrete 3.5% NaCl and 180 g L(-1) of H(2)SO(4) with 70 ppm of chloride ions solutions were used to simulate the synthetic medium. The initial electrochemical variables of the steel and pH, chlorides and sulfates profiles were measured according to the concrete depth. The morphology of the corrosive attack was determined electron microscopy (SEM), and the composition of the corrosion products was determined via scanning zer and an X-ray diffractorneter (XRD). The protective power of the corrosion products was evaluated through anodic polarization curves in a saturated Ca(OH)(2) Solution. The results from XRD and SEM show that all the resulting corrosion products correspond to lepidocrocite, goethite and magnetite mixtures: moreover, akaganeite was also identified under natural and simulated marine environments. Siderite was only detected in samples exposed to a natural marine environment. Concerning the protective nature of the corrosion products, these show lower performance in a simulated industrial environment, where the corrosion rate of the steel is up to 1.48 mu m year(-1). (C) 2008 Elsevier B.V. All rights reserved.