Study of the influence of some organics as thiourea derivatives and butindiol in steel pickling baths

Abstract

The corrosion inhibition effect of the following organic additives: 2-butin-1,4-diol (BD), N,N 0 -dimethylthiourea (DMTU), N,N 0 -diethylthiourea (DETU) and N,N 0 -diisopropylthiourea (DITU), in steel pickling baths (sulphuric acid solutions) was studied by means of weight loss and electrochemical measurements like open circuit potential (OCP), polarization curves and impedance spectroscopy (EIS). A significant decrease in the corrosion rate was observed in presence of the investigated compounds depending on the nature and the concentration of the additives. The weight loss experiments show an inhibitory efficiency that reaches values beyond 98 %. The protective effect increases with the enlargement of the lateral chain size in the case of the thioureas. The electrochemical experiments show also a protective effect of the organic additives against corrosion. Their adsorptive behaviour is found to follow the Langmuir model.