Corrosion challenges towards a sustainable turning of stainless steel under different cooling methods

Metalworking fluids are mostly produced based on mineral oils. Such fluids are not naturally biodegradable and contain large amounts of ingredients that are harmful to the environment and human health. They are therefore classified as hazardous waste and must be safely disposed of. Mineral oil-based fluids are the main unsustainable element of the metal cutting machining process. This study aims to investigate the influence of cutting parameters and cooling techniques (dry, conventional emulsion, minimum quantity lubrication (MQL), and MQL combined with vortex tube cooling) on the corrosion resistance of AISI 316L austenitic stainless steel. Electrochemical corrosion, and metallographic tests were performed. Surface chemical composition using energy-dispersive X-ray spectroscopy (EDS) before and after corrosion testing, and surface morphology using scanning electron microscopy (SEM) were analysed. The applied cooling method has a significant influence on both the elemental composition and the electrochemical behaviour of the machined surfaces. The role of machining-induced surface chemistry in localized corrosion behaviour is crucial. MQL-based techniques providing the most favourable electrochemical parameters and dry machining resulting in the poorest performance. The MQL combined with vortex tube cooling achieved the lowest corrosion rate (≈0.0308 mm/year), while dry machining exhibited the highest (≈0.0833 mm/year), highlighting the effectiveness of the hybrid sustainable cooling approach. The potential of MQL-based techniques as efficient and environmentally friendly alternatives to cooling has been confirmed.