Microbiology of metalworking fluids: what we know and lessons to be learnt

Water-miscible metalworking fluids are an essential component of many manufacturing processes. During their lifetime they are subject to permanent changes in their physical and chemical characteristics. Due to their high content of water and their chemical composition in use, metalworking fluids (MWF) are prone to microbial life, i.e. the proliferation of bacteria and fungi. The microbial activity leads to significant changes in the chemical composition of the MWF, which can result in the loss of their technical properties. This paper briefly discusses the influences of microbial contamination on the technical quality of MWF and presents common monitoring systems for the detection of microorganisms. Finally, measures are described that can be taken to protect MWF from damage caused by high microbial loads in daily practice. In a short outlook, alternative research approaches are mentioned that aim at sustainable use of MWF.