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 realconcern for many wet-process industries. The effects of rouging, corrosion, and biofouling are costly problems on the surfaceof stainless steel, the most common material in processing plants. We have developed a corrosive treatment that is indicativeof the wet-processing conditions commonly used in food processing, pharmaceutical, and bioprocess applications to test theeffects 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 thevariation in bacterial attachment on each finish. A duplicate set of samples was exposed to the corrosive treatment to simulateprocessing conditions. All samples were examined by visual inspection and electron probe microanalysis for surfacecharacteristics and elemental composition of the stainless steel finishes. Samples were exposed to natural bacterialpopulations from chicken carcass rinses to allow growth of bacteria and development of biofilms on the surfaces. The kineticsof bacterial growth during surface exposure was followed by UV-visible spectrophotometry, and counts of bacteria and earlybiofilm formation were determined from micrographs following scanning electron microscopy. Bacterial attachment on eachsurface finish was measured and compared with controls and the five other finishes. Exposure to the corrosive treatmentconditions resulted in changes in the numbers of bacteria that attached to each surface finish. After exposure to corrosivetreatment, 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 weresignificantly most resistant, before and after exposure to corrosive treatment, than the seven other finishes tested.