Evaluation of volatile corrosion inhibitors in the presence of condensation water by electrochemical methods

Abstract

Volatile corrosion inhibitors (VCI) are a means of temporary corrosion protection based on the release of inhibitors from films, papers, diffusers or oil to the gaseous phase. By adsorption on a metal surface, the inhibitors prevent degradation of the primary oxide layer and impede corrosion. Thus, VCI provide corrosion protection for high-quality goods and semi-finished parts made from metals during transportation and storage. The application of oil on the metal surface for corrosion protection and its removal can be avoided. Due to rapid volatilization of the VCI after unpacking, no costly cleaning of parts prior to further use is required. In a new approach for evaluation of the protective effect of VCI, a metallic sample is exposed in a small chamber filled with air alongside a VCI-containing product. The air is humidified and the sample is cooled down under dewpoint, which leads to condensation of humidity and represents corrosive stress. The state of the metallic surface under the condensed water film is characterized by electrochemical methods. The present work demonstrates the evaluation of the anticorrosive effect of various VCI-films on mild steel. In summary, the application-oriented test allows for quick and quantified evaluation of VCI-containing products with a tabletop device.