Galvanic Corrosion of Steel in Agitated Vessels Used in Fertilizer Industry

Abstract

Rates of mass transfer controlled Fe/Cu galvanic corrosion at the wall lining of a cylindrical agitated vessel in different fertilizer electrolytic media were studied. Variables investigated are impeller rotation speed, impeller geometry, electrolyte type, electrolyte concentration, area ratio (anode/cathode), electrolyte temperature, and effect of polyethylene oxide (drag reducing polymer) as a corrosion inhibitor. The corrosion rate was determined by following the change of the concentration of anode metal ions (Fe⁺⁺) in the electrolyte with time. Scanning electron microscopy (SEM) was carried out for steel sheets subjected to different electrolytes. The results showed that the galvanic corrosion rate increased with increasing the impeller rotation speed, the electrolyte concentration, and temperature. The presence of polyethylene oxide decreased the rate of corrosion by 11–35.21% depending on polymer concentration and operating conditions. Axial flow impeller produces corrosion rates higher than that with the radial flow type under the same operating parameters. Application of the results in the design of agitated vessels handling fertilizer media was discussed.