This document discusses electrochemical machining (ECM) and tool profile correction. It explains that ECM involves controlled atomic dissolution of a conductive workpiece through an electrolyte using a shaped tool. The material removal rate depends on factors like current, time and material properties. While ECM is self-regulating, variations in parameters like electrolyte resistivity can cause non-uniform gaps. Tool profiles require correction beyond a simple inverse shape due to multiple influencing factors. Empirical methods have been developed to predict the needed tool profile for proper part machining.