CORROSION INHIBITION OF IRON IN ACID-SOLUTIONS BY BIOLOGICAL SIDEROPHORES

Four siderophores isolated from bacteria have been studied as possible corrosion inhibitors for iron in deareated 1N HCl. These compounds ar e aerobactin, enterobactin, parabactin, and rhodotorulic acid. Polariz ation measurements and ac impedance studies show that all four compoun ds are inhibitors, with the order of effectiveness being rhodotorulic acid < aerobactin < enterobactin < parabactin. X-ray photoelectron spe ctroscopy surface analysis with one of the siderophores, rhodotorulic acid, shows that it chemisorbs at the iron/HCl interface. Enterobactin and parabactin are the most effective corrosion inhibitors of the fou r because they have the optimum combination of relatively high values of pK(al) and the largest molecular cross-sectional areas.