INHIBITION OF PIPELINE STEEL CORROSION IN ALKALI AND NEUTRAL WATER SOLUTIONS AT DIFFERENT TEMPERATURES BY SODIUM MOLYBDATE

Abstract

Effect of sodium molybdate on the pipeline steel corrosion inhibition in the aerated alkali (pH 11) and neutral (pH 7) water solutions at temperatures from 30°C to 140°C has been investigated by mass loss, potentiodynamic polarization and electrochemical impedance spectroscopy methods. Sodium molybdate was added in concentrations: 200 ppm, 350 ppm and 500 ppm by mass. The steel samples were evaluated mass loss measurements after 4, 8, 12, 24, 48, 72 and 96 hours of immersion at 30°C; after 4 hours at 60°C, 100°C and 140°C. The experimental results showed that, sodium molybdate are effective for inhibition against steel corrosion by the formation of MoO2 film in neutral solutions-containing oxygen at the different temperatures. On the contrary, sodium molybdate is unprofitable for steel corrosion inhibition in the alkali solutions at the different temperatures.