ABSTRACT
This chapter covers the recycling of both types of metalworking fluids: straight oil and water diluted. The strategies for recycling these fluids are similar, but each type of fluid presents its own challenges for recycling. The term straight oil has been used in the metalworking industry for many decades. Straight oil is a misnomer, as this term leads the untrained user to believe that the fluid is nothing more than oil. Straight oil metalworking fluids are developed in a process similar to other industrial blended oils, such as motor oils, lubricating oils, and hydraulic oils. Positively charged contaminants in water are very reactive and are fully reacted in less than 60 s in the metalworking fluid. Therefore, the best solution is to eliminate them from the diluting water before it enters the metalworking mixture. Another strategy is to complex them with a chelate, such as sodium salts of ethylenediaminetetraacetic acid (EDTA).
