Formation of anodic oxide coatings, electropolishing, and electrochemical machining, being all the technologies based on the processes of metal oxidation with formation of either solid, or soluble products.
Electropolishing started to develop as an alternative to mechanical and chemical polishing. The priority of E.I. Spitalsky’s 1910 patent (if formal priority is really of interest) requires further clarification. At this stage we rely on opinion of Pierre Armand Jacquet (1906-1967), who presents the following list of the earliest contributions:
Jacquet’s note “Electrolytic Method for obtaining Bright Copper Surfaces” (Nature. 1935. V. 135. P. 1076) is believed to report for the first time the image of electropolished metal.
Electrochemical machining was invented not later than in 1924, as we can judge from the article of M. Pirani and K. Schröter “Elektrolytische Formgebung von harten metallischen Gegenständen” (Metallkunde. 1924. Bd. 16. S. 132-133). More frequently mentioned priority is 1929 patent GB 335003A “Method and apparatus for the electrolytic treatment of metals” authored by W. Guseff (Vladimir Nikolaevich Gusev (1904-1956)). Jointly with Lev Alexandrovich Rozhkov, Gusev also authored 1928 Russian patent of a similar content.