: Bischoff, J.; Hennemann, O.-D.; Kock, E.; Wit, F. de

Abstract
Non-chromatic anodizing processes were investigated with respect to their applicability for surface preparation of aluminium for structural bonds in the aircraft industry. Detailed TEM (Transmission Electron Microscopy) analysis of ultrathin cuts made from the oxide layer with special respect to the interface oxide/polymer show the interdependence between process parameters and oxide morphology. The strength of corresponding bonded samples was investigated in peel-tests. Oxides with smooth surfaces and small pore diameters result in low strength values. The results allow for the deduction of a hyphothesis regarding the mechanical behaviour in the interphases. The strength of these adhesive bonds is dependent from the stiffness properties in the interphases, which are determined by the oxide morphology and the polymer structure at the interface. A combination of phosphoric and sulphuric acid gave the best results and reached requirements of the aircraft-industry.