Elimination of organic solvents for decreasing of metal components by use of a novel microwave plasma

Currently metallic parts which have been through machining and fabrication processes are degreased by means of organic solvents (e.g. perchloroethlylene, trichloroethylene) before further treatment, coating or final delivery. Although these organic solvents remove oil that covers the part, these chemical products create environmental and health risks. In the DRYDEG project, funded by the EC under the "CRAFT" Programme, the aim is to avoid the use of organic solvents for oil removal from mechanized metallic parts by using a novel plasma. APNEP (Atmospheric Pressure Non Equilibrium Plasma) operates at or near atmospheric pressure and uses relatively cheap commercial microwave engineering at a frequency of 2.45 GHz to create high concentrations of chemically reactive radicals that remove oils from parts. The plasma chemistry has been shown to be very similar to that achieved in vacuum plasmas but without the expense and inconvenience of a vacuum system. Successful degreasing trials have been performed on metallic parts (carbon steel and aluminium) from the automotive and aeronautic industries, working with various parameter values (gas flow, type of gas, power, distance, type of grease/oil etc) in order to arrive at the best conditions of treatment. Parts which have been degreased in the APNEP device have been processed at an industrial site without problems. In addition, the emissions produced in the process have been analysed showing very low concentration of organic compounds, always under the legal limits.