Effects of corrosive treatment on stainless steel surface finishes and bacterial attachment

Corrosion, an important factor for the durability of a metal finish after exposure to water and chemicals, is a real concern for many wet-process industries. The effects of rouging, corrosion, and biofouling are costly problems on the surface of stainless steel, the most common material in processing plants. We have developed a corrosive treatment that is indicative of the wet-processing conditions commonly used in food processing, pharmaceutical, and bioprocess applications to test the effects of surface corrosion on bacterial attachment. Samples of surface finishes (electropolished, steel-ball burnished, glass-beaded, acid-dipped, steel-shot burnished, and sandblasted) were compared with mill finish controls to determine the variation in bacterial attachment on each finish. A duplicate set of samples was exposed to the corrosive treatment to simulate processing conditions. All samples were examined by visual inspection and electron probe microanalysis for surface characteristics and elemental composition of the stainless steel finishes. Samples were exposed to natural bacterial populations from chicken carcass rinses to allow growth of bacteria and development of biofilms on the surfaces. The kinetics of bacterial growth during surface exposure was followed by UV-visible spectrophotometry, and counts of bacteria and early biofilm formation were determined from micrographs following scanning electron microscopy. Bacterial attachment on each surface finish was measured and compared with controls and the five other finishes. Exposure to the corrosive treatment conditions resulted in changes in the numbers of bacteria that attached to each surface finish. After exposure to corrosive treatment, significantly greater numbers of bacteria attached to steel-ball burnished and glass-beaded finishes. However, the control mill finish and electropolished samples had fewer bacteria attached after exposure. Electropolished samples were significantly most resistant, before and after exposure to corrosive treatment, than the seven other finishes tested.