An Investigation of Microbiologically Mediated Corrosion of Copper-Nickel Piping Systems Selectively Treated with Ferrous Sulfate

Microbiologically induced corrosion in 90/10 Cu-Ni pipes was evaluated using estuarine water from the Gulf of Mexico at the mouth of the Pascagoula River, maintained at a flow rate of 3-6 ft/sec over an 8-month period. The impact of surface preparation, batch FeSO4(50 ppb Fe²⁺for 48 hours) pretreatment and intermittent treatment was evaluated. Surface deposits were characterized by scanning electron microscopy and energy-dispersive x-ray fluorescence spectrometry. Water analyses included pH, dissolved oxygen, dissolved sulfide and sulfate, total organic carbon, total suspended solids and dissolved heavy metal analyses, as well as quantification of bacteriological components. Batch FeSO4treatment did not result in a persistent increase in surface-bound iron or decreased localized corrosion. Surface pitting appeared to be associated with accumulations of chlorine, sulfur, and microbiological colonization.