Comparative Study of Volatile Corrosion Inhibitors in Various Electrochemical Setups

Volatile corrosion inhibitors (VCIs) are increasingly used in closed systems affected by atmospheric corrosion. In order to achieve a satisfactory level of protection, an inhibitor must be present in a sufficient concentration that should be determined experimentally. Electrochemical measurements are indispensable in corrosion studies examining the protection efficiency of corrosion inhibitors. Volatile corrosion inhibitors are often examined by electrochemical measurements conducted in a bulk of electrolyte, although they protect metal surfaces from atmospheric corrosion where a thin film of electrolyte is present. The aim of this work is to study the protection of carbon steel by two VCIs on different types of electrodes that allow electrochemical tests in a thin electrolyte film and to compare the obtained results with those obtained in a larger volume in a classical electrochemical cell. For this purpose, disc and comb-like electrodes are used. The investigations are carried out in two corrosion media simulating either a marine or urban polluted atmosphere. Studies are performed on low-carbon S235JR steel, which is typically used for crude oil tank bottoms that often suffer from atmospheric corrosion and are increasingly protected by VCIs. Two benzoate-based VCIs recommended for such application are selected for this study.