Electropolishing solution and methods for its use and recovery

The sizing, shaping, and surface finishing of metals for complex parts such as turbine blades, impellers, vessels, and the like has often proven to be a challenge. One commonly used method for shaping and finishing metals and metal alloys is etching. However, most commonly used etching solutions employ materials such as hydrofluoric acid that are hazardous to handle and difficult and expensive to dispose of. An alternative to etching is electropolishing, but there is a need for electropolishing materials and methods that achieve high surface smoothness, and are less expensive, less corrosive, and more environmentally friendly than current etching materials and methods. An electrolyte solution containing an alkylene glycol and a chloride salt is useful for electropolishing metal substrates. An electropolishing method using the electrolyte solution is effective for polishing a varied of metals, including titanium and noble metals. The method avoids the handling and disposal challenges associated with previous methods using etching solutions containing hydrofluoric acid. A method of recycling the spent electrolyte solution is also described.