Method Development for Evaluating Microbiological Growth on and Attachment to Aluminum Air Conditioner Evaporator Core Surfaces 2006-01-1645

Corrosion failures of aluminum air conditioner evaporator cores have been reported in regions where the climate is relatively warm and humid. Microbiologically-influenced corrosion [MIC] has been implicated in these failures. Application of surface-treatment chemicals may inhibit microbiological (bacterial) growth and/or attachment, thereby reducing the potential for MIC.

In this study, two laboratory methods were developed to evaluate selected surface-treatment chemicals for their ability to inhibit bacterial growth and reduce bacterial attachment to treated surfaces. Using the developed methods, two controlled-atmosphere brazed aluminum core materials and three surface-treatment chemicals were evaluated. Neither of the untreated core materials was found to inhibit the growth of the bacteria tested. Among the surface treatments, Product A did not appear to be inhibitory towards either of the bacterial species, however attachment of bacteria to the treated aluminum coupon was reduced by 32-39% after one hour of contact and by 57-67% after 48 hours of incubation. Product B appeared to be inhibitory towards both of the bacterial species tested, but did not seem to affect bacterial attachment. Product C also appeared inhibitory towards both species tested and reduced attachment by 60-80% after 48 hours of bacterial contact. These results were generally consistent with manufacturers' claims about the functionality of their products.