11008 Chloride-Induced Corrosion of Reinforcing Steel in Concrete: Electrochemical Modeling of Initial and Limiting Corrosion Rates

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Product Number: 51300-11008-SG

ISBN: 11008 2011 CP

Author: Goli Nossoni, Ronald Harichandran and Scott C. Barton

Publication Date: 2011

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The high alkalinity of concrete can prevent reinforcing steel in concrete from corroding. However, corrosion will commence when the [Cl-]/[OH-] ratio reaches a threshold of about 0.6. The aim of this paper is to evaluate the initial corrosion rate of steel due to chloride penetration into the concrete pores. The corrosion process is very complex and modeling is often based on observation or speculation rather than detailed modeling of the chemical processes involved.

Corrosion starts with an initial rate of corrosion when the chloride concentration reaches a threshold value. This initial corrosion rate is modeled using experimental test data. Comprehensive experimental tests were conducted to understand the behavior of steel in alkaline media in the presence of chloride ions and how much this behavior changes as the chloride concentration increases. Understanding this behavior enables modeling of the initial corrosion rate of steel inside concrete which is highly dependent on the chloride concentration.

Corrosion cannot continue at this rate for a long period and will eventually slow down to the limiting current rate that depends on the concentration of oxygen inside concrete at the location of the steel bar. The limiting corrosion current that mostly governs the corrosion rate during the corrosion period is highly dependent on the initial corrosion rate, and it is therefore important to accurately estimate the initial corrosion rate.

Key Words: Initial corrosion rate, limiting corrosion rate, polarization curve, chloride, steel, concrete.