ECM is a method of removing metal by an electrochemical process. It is used for working extremely hard materials or materials that are difficult to machine using conventional methods. Its use is limited to electrically conductive materials; however, this includes all metals. ECM can cut small or odd-shaped angles, intricate contours or cavities in extremely hard steel and exotic metals such as titanium, hastelloy, kovar, inconel and carbide.

ECM is similar in concept to Electrical discharge machining in that a high current is passed between an electrode and the part, through an electrolyte; however, in ECM there is no tool wear. The ECM cutting tool is guided along the desired path very close to the work but it does not touch the piece. Unlike EDM however, no sparks are created. The workpiece is eroded away in the reverse process to electroplating. Very high metal removal rates are possible with ECM, along with no thermal or mechanical stresses being transferred to the part, and mirror surface finishes are possible.