Ascorbic Acid as Corrosion Inhibitor for Steel in Alkaline Media Containing Chloride Ions

The investigation of nature-designed molecules and blends of naturally synthesized chemical compounds as possible inhibitor candidates for reinforcing steel in concrete is of raising interest due to the health and environmental hazards involved in the use of most inorganic corrosion inhibitors. In the alkaline media of concrete pore solution, the oxide film is present on the surface of the reinforcing steel. The ingress of chloride ions and/or carbon dioxide into the concrete destabilizes the passive film leading to a higher rate of metal dissolution through the appearance of localized forms of corrosion. This study investigates pitting inhibition with ascorbic acid (AA), by analyzing the polarization curves in the presence and absence of the inhibitor. Inhibition action was evaluated from its ability to suppress the cathodic reaction of oxygen reduction as well as from its ability to suppress the onset of pitting. The mechanism of the inhibitor action was deduced by comparative interpretation of the inhibitor’s molecular properties and the data obtained from electrochemical experiments.