Sievers, S. Krupka, N. Reschke, D. Saegebarth, S. Schaffran, J. Schalwat, M. Schilling, P. Schmökel, M. Steinhau-Kühl, N. Vogel, E. Weise, H. Wiencek, M. van der Horst, B. JACoW Publishing Geneva, Switzerland 2226-0366 978-3-95450-194-6 10.18429/JACoW-LINAC2018-TUPO028 English 384-387 TUPO028 cavity FEL vacuum SRF linac Contribution to a conference proceedings 2019 2019-01 https://doi.org/10.18429/JACoW-LINAC2018-TUPO028 http://jacow.org/linac2018/papers/tupo028.pdf For the European XFEL 10² accelerating modules were built and tested. Several accelerating modules had to be reworked due to different kinds of non-conformities. The extent of this rework varied greatly. At the end of production four accelerating modules could not be qualified in time before the tunnel installation was to be finished in September 2016. Meanwhile the cavity strings of two of these accelerating modules have been disassembled in the DESY clean room. The cavities have been retreated at DESY either by additional high pressure water rinsing or BCP flash chemical treatment. All cavities were vertically tested and 15 out of 16 were qualified for the reassembly of the cavity strings. One accelerating module will be reassembled completely and tested until the end of 2018; the other will follow in the first half of 2019. We report on retreatment procedures and performance of these cavities.