THE INFLUENCE OF WATER CONCENTRATION ON THE CORROSION OF LOW ALLOY STEELS IN THE SYSTEM METHANOL - ETHYLENE GLYCOL - FORMIC ACID

Abstract

The behaviour of three types of steel with a variable carbon content (from 0.2 to 0.4%) is studied in medium of methanol - 10% ethylene glycol - 8% formic acid with water concentration between 2% to 10%. The weight losses are measured; also the polarisation anodic and catodic curves are plotted and the corrosion parameters are established. The corrosion compounds are analysed by IR spectra, X-ray diffraction and chemical analysis. With the obtained data, a corrosion mechanism is assigned and an optimum ratio between water and acid is established in order to obtain the passive oxyhydroxylic layer.