Abstract: The device proposed for cleaning metal surfaces consist of pad (12, 34, 91) of insulating material held between a beak-shaped (11, 52, 94) electrode (10, 26, 46) and the metal surface (8) to be cleaned, plus a low-voltage a.c. power supply (2) which is connected via the other electrode to the metal (7). A pump supplies the pad with a highly corrosive, high-density, acid solution. The pad consists of a relatively thick hose or tape. The device has slots (36) into which the gases and vapors produced during cleaning are drawn by an extractor fan (40) and then passed through a washing bottle (41) where they are cleaned. The electrode may have various shapes, and it is possible to replace the tip (28, 94, 98). The electrode is preferably designed with bores through which the acid solution can be fed.