Efficiency of Vapor Phase Corrosion Inhibitors for Ferrous Metals in Neutral and Alkaline Solutions

摘要

The ability of some typical vapor phase corrosion inhibitors (VCI) to protect mild steel toward corrosion in neutral and alkaline solutions was studied. The inhibition mechanism was investigated by electrochemical methods such as open-circuit potential (OCP) measurements, polarization curves, and electrochemical impedance spectroscopy (EIS) exemplary in aerated cyclohexylamine salt solutions with different weak and strong acid anions. It was found that weak acid anions like benzoate play a dual role in the inhibition mechanism: under near-neutral conditions they can occlude dejects in the air-formed oxide layer by precipitation of insoluble salts or basic salts with ferric ions, and in strong alkaline solutions they act as a buffer of pH inside the defect sites and limit the localized accumulation of protons. However, in the pH range between 9.0 and 10.3, passivation of mild steel is not possible with all investigated cyclohexylamine salts. [PUBLICATION ABSTRACT]