Corrosion Behavior of AISI 1045 Carbon Steel in Metalworking Fluids Containing Pseudomonas xiamenensis

Microbial contamination of aqueous metalworking fluids (MWFs) is of significant concern in metal process industries. In this study, a dominant Pseudomonas sp. strain ( P. xiamenensis ) was isolated from waste metalworking fluids (WMWFs) and the biodegradation of model MWF was studied under the influence of P. xiamenensis. Results showed that nitric additives in MWF were severely degraded by bacteria, leading to a significant increase in the turbidity of the MWF. The occurrence of microbially influenced corrosion of AISI 1045 carbon steel in MWF containing P. xiamenensis , was proven by morphological analysis and electrochemical characterization. The corrosion rate of the metal in MWF in the presence of bacteria was three-fold greater than in the absence of bacteria. Electrochemical results and surface analysis elucidated that the additive film was decomposed by P. xaimenensis adhered to the steel surface and a biofilm, which was controlled by diffusion replacing the additive film. The biofilm was reinforced by the reaction of metabolites and Ca 2+ and seriously localized corrosion behavior was observed in carbon steel immersed in the bio-contaminated MWF due to the microbial influence.