A considerable amount of research on microbial- induced corrosion has been conducted by industries that employ buried pipelines and underground structures (King and Miller, 1971; Tatnall, 1981; Iverson and Olson, 1983; Iverson, 1984; Ford and Mitchell, 1990). Since the sulfate-reducing bacteria (SRB) has been considered the major bacterial species in causing metal corrosion under anaerobic environments (Crombie et al., 1980; Pankhania, 1988; Ford and Mitchell, 1990; Hao et al., 1996), most of the past studies concentrated on the corrosion problems caused by SRB encountered in those environments. Little is known about the potential of this type of bacteria to corrode metals under aerobic situations. Recently, a few researchers have studied SRB corrosion problems in aerobic environments. Hardy and Bown (1984) suggested that the most aggressive conditions associated with SRB were those which were not entirely anaerobic, but where small quantities of oxygen might be present from time to time. Scott and Davies (1992) reported high counts of SRB on the corroded steel columns in a medical research building. They found that SRB could survive in an aerobic environment with the assistance of oxygen depletion bacteria. Zhu et al. (1994) reported their findings of biofilms and the SRB counts on metal surfaces based on a preliminary survey conducted in animal buildings. The results from these studies showed that sulfate-reducing bacteria could survive and contribute to metal corrosion problems in environments with the presence of oxygen. Feed materials, dust, moisture, and animal feces are abundant in animal buildings and provide adequate nutrients for bacterial growth on metal surfaces in these buildings. No metal substratum can be totally immune from microbial colonization in animal building environments. A knowledge of the growth of SRB in animal buildings, as well as information regarding metal corrosion when exposed to these bacteria, will help estimate the probability of metal deterioration caused by these microbes and provide information on how to prevent it. This article reports the experimental results of a study on the potential of metal corrosion by SRB during a two- year field exposure study in three animal buildings and one environmentally controlled building. The colonization, growth, and decay of SRB on metal surfaces were investigated. An analysis of the corrosion products on corroded metal surfaces using X-ray photoelectron spectroscopy was also done to determine if the corrosion products were produced by SRB. MATERIALS AND METHODS SAMPLE MATERIALS AND PLACEMENT Six types of metal samples were used in the field exposure test (uncoated 1010 carbon steel, galvanized steel, prepainted G90 hot dipped galvanized steel, uncoated Galvalume, prepainted Galvalume, and pure zinc). The metal coupons were 25 mm × 63.5 mm. Ten sets of metal coupons were placed in each building. Each set consisted of six pieces (one of each metal type) so sets could be removed periodically for analysis over a period of two years. A STUDY ON THE POTENTIAL OF METAL CORROSION BY SULFATE-REDUCING BACTERIA IN ANIMAL BUILDINGS J. Zhu, G. L. Riskowski, R. I. Mackie ABSTRACT . The potential of sulfate-reducing bacteria (SRB) to cause metal corrosion in animal buildings was examined in this study. An analysis was done on the bacterial colonization and the corrosion products on the surfaces of metals exposed to three animal buildings and one environmentally controlled building over a two-year period. Data from this study showed that the levels of SRB on metal surfaces were low after two-year’s exposure (maximum count: 1.7 × 10 4 /cm 2 ). SRB colonization levels after two years were not sufficient to corrode metal products exposed in animal environments. In addition, metal surface analysis data using X-ray photoelectron spectroscopy showed that the corrosion compounds formed on the surfaces of different metals were not due to the SRB-induced corrosion mechanisms. These compounds were mainly oxides and carbonates (FeO, Fe 2 O 3 , Fe 3 O 4 , and Fe(CO) 5 on iron samples; ZnO and ZnCO 3 on galvanized steel samples; Al 2 O 3 , ZnO, and ZnCO 3 on Galvalume samples), and were normally generated due to the classic types of corrosion mechanisms. Some sulfur was present to form ZnS on the galvanized steel samples, but might not be attributed to SRB. The origin of this sulfur was not clear. Keywords. Animal housing, Sulfate reduction, Bacteria, Metal, Corrosion. Article was submitted for publication in February 1998; reviewed and approved for publication by the Structures & Environment Division of ASAE in March 1999. The authors are Jun Zhu, ASAE Member Engineer, Assistant Professor, University of Minnesota, Southern Experiment Station, Waseca, Minn.; Gerald L. Riskowski, ASAE Member Engineer, Professor, Agricultural Engineering Department, University of Illinois, Urbana, Ill.; and Roderick I. Mackie, Professor, Department of Animal Sciences, University of Illinois, Urbana, Ill. Corresponding author: Dr. Jun Zhu, University of Minnesota, Southern Experiment Station, 35838- 120th Street, Waseca, MN 56093; voice: (507) 835-3620; fax: (507) 835- 3622; e-mail: zhuxx034@tc.umn.edu. Transactions of the ASAE © 1999 American Society of Agricultural Engineers 0001-2351 / 99 / 4203-777 777 VOL. 42(3): 777-782