Semiconducting properties of surface-treated titanium and their effect on peel resistance: Experimental and modelling studies

Adhesively-bonded titanium components enable new design concepts in lightweight engineering but often lack long-term joint durability and endurance. Major challenges are related to the fact that the titanium/adhesive interface is susceptible to environmental ageing which leads to interfacial deadhesion. In the present work, the issue is addressed from the standpoint of semiconducting properties of surface TiO2 films. Examination of surface treated, anodized cp-Ti has been conducted using electrochemical impedance spectroscopy (EIS). Semiconducting properties of titanium oxide films were derived from Mott-Schottky analysis whereas roller-peel tests were considered for joint strength assessment before and after accelerated ageing in climate chambers. The experimental study is complemented by a computational study on the adhesion force distribution during roller peel testing based on a cohesive zone FEM model. The studies show clear indication for a complex interaction between the adhesion contributing underlying physio-chemical mechanisms. Crucial insights into the electrochemistry at the respective interfaces and their relevance for joint design are provided.