Local electrochemistry of reinforcement steel - Distribution of open circuit and pitting potentials on steels with different surface condition

Local electrochemical measurements (open circuit potential (OCP), cathodic and anodic polarization curves, pitting potentials) were performed at random locations on 1 m long ribbed steel bars with different surface conditions. The results show that the local OCP values are statistically distributed. The standard deviation was found to be 45 mV for “as received” surface condition, decreasing to 10 mV only after prolonged immersion in sat. Ca(OH)2. A model based on local variations of the reduction current density could explain the variations in local OCP and allowed predicting the overall global OCP of the long bars when completely immersed in solution.