flender industriegetriebe gmbh H3-HV-25-A Helical gear reducers H3

Flender/Flender Gear Units/Helical gear reducers H3

e metal coatings on the substrate through activating pretreatment, investigation of individual process parameters as regards their effect on adhesion, production of metalorganic compounds for the use of rotic pretreatment solutions, studies of the life of such solutions and their regene- rability, anzbalancing out the evaporation and condensation rates in individual processing steps under practice-oriented conditions. Special test installations were required for this purpose which enable sam les made of various materials to be channelled into the system protected by inert gas, treatefand cleaned. Based on the experience gained from these tests, larger machines were then constructed and operat- ed on pilot scale, in order also to be able to investigate technological parameters, such as the convective mass exchange, the electrode geometry, the drag-out of solutions, the service life of the solutions in continuous operation, chemical consumption, etc. universally applicable processing cycle was to be derived from the knowledge gained in these studies, in order to make this concept useful for wide range of substrate materials. 3. Results Precleaned workpieces which are to be electroplated with aluminium in an aprotic solution must be reliablyfreed from water. Instead of being treated with CFCs,as is the current practice, the water-wetted surfaces can first be cleaned with polar solvent, .. acetone, in closed system and this solvent subsequently rinsed off with toluene. This water removal procedure is particularly compatible with the environment and offers excellent prere uisites for the highly adhesive aluminium plating of many substrate materials. The adhesion oqthealuminium coat- ing can be further improved by pretreating the workpieces wetted with toluene in an electro- less trialkylaluminium solution and, if necessary, seeding them by chemical reduction. In this way, adhesion-promoting intermediate coatings of toxic metals, such as coppe