Corrosion can be defined as the degradation of a material due to reaction with its environment. It is a spontaneous process. The driving force of corrosion is the tendency of the metals to have lower energy. Corrosion control is a concern whenever water is present in a metalworking fluid. Heat removal is one of the most important functions of a metalworking fluid. Water-based coolants have greater capacity for removing heat than oil. However, water alone in contact with freshly machined metal leads to corrosion.