Degreasing bath care in the steel and metal working industry Original Research Article

Degreasing is an important process step in surface treatment of metal products. For treatment of degreasing baths membrane filtration is a state-of-the-art technology, but still companies, especially small ones, hesitate to establish a membrane filtration for their degreasing baths. In this article the different aims and strategies for membrane filtration of degreasing baths are discussed. The steps that have to be taken to develop a reliable membrane process are described: selection of the suitable membrane in a membrane screening, determination of process parameters in pilot experiments, preferably at the industrial line, concept development and plant realisation. Two complementary examples of membrane filtration for degreasing bath care are discussed: The first example is an investigation of degreasing bath care in the steel industry with recovery of all cleaning agent components including surfactants. The second example concerns degreasing bath care in small and medium metal working enterprises. Because degreasing bath volumes and potential cost savings are smaller, process development costs and investment costs have to be smaller as well. In this case, membrane filtration without recovery of surfactants is advantageous.