The influence of water concentration on the corrosion of low alloy steels in the system methanol-ethyleneglycol-propionic acid

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% ethyleneglycol - 5% pro pionic acid with water concentration between the values 1% to 5%. The weigh t losses are measured; also the polarisation anodic and catodic curves are plotted and the corrosion parameters are established. The methods used for the analysis of the corrosion compounds are IR spectra, X-ray diffraction a nd chemical analysis. Finally, a corrosion mechanism is proposed and the op timum ratio between water and acid is established in order to obtain the pa ssive oxyhydroxylic layer.