Quality Control of the Electro Polishing Process at DESY

The technology of electro-polishing of super-conducting resonators made from Niobium is foreseen as basic surface preparation technology for the XFEL accelerator project at DESY. Here about 1000 resonators will be build and installed into the accelerator section. For an industrial application of this technique a quality control has to be developed and established. A method to control the acid quality and improve the life time of the acid is under development. We report on the test setup and measurements done on samples and the implementation of this quality control to the DESY electro polishing process.