Use of vapour phase corrosion inhibitors in packages for protecting mild steel against corrosion

Some aspects of the passivation of mild steel in the presence of selected vapour phase corrosion inhibitors (VCIs) were considered. In particular their ability to vapourize was evaluated by sublimation tests and their role in the inhibition mechanism of mild steel was investigated by electrochemical methods such as open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) measurements. In the presence of some carboxylates, amines and azoles alone and as mixtures a protective layer can be formed on mild steel in neutral and alkaline solution. It was shown that the passivation mechanism strongly depends on the pH of the solution. In addition the influence of contaminants from industrial alkaline cleaning baths on the protective properties was analyzed.