Metal parts are prepared for subsequent work steps by removing the detrimental oxide layer in the KSK etching system. This cleaning effect is used to improve the bonding of subsequent coats to the unfinished part and prepares the bonding surfaces safely. The chemicals used in the etchant are processed according to occupational health and safety regulations as well as environmental regulations. State of the art filter, exhaust and wastewater systems ensure that there is no harm to humans or the environment.