Journal Pre-proof 1 A methodology for characterizing the electrochemical stability of DLC coated interlayers and interfaces Emilija Ilic 1,2 , Ainhoa Pardo 1 , Thomas Suter 1 , Stefano Mischler 2 , Patrik Schmutz 1 , Roland Hauert 1* 1 Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Joining Technologies and Corrosion, Switzerland 2 EPFL, Ecole Polytechnique Fédérale de Lausanne, Tribology and Interfacial Chemistry Group, Switzerland * Corresponding author: roland.hauert@empa.ch Abstract DLC coatings are often deposited on Si and Cr based adhesion-promoting interlayers to mitigate stress at the DLC/substrate interface. Interlayers reduce the likelihood of mechanical coating delamination. However, their chemical stability at miniature DLC coating defects, such as pores and micro-pinholes, may be adversely affected in a corrosive environment, such as the human body where DLC coated implants are envisaged. An experimental methodology is presented for accessing and characterizing the electrochemical reactivity of buried interlayers and interfaces. The interlayer, with its interfaces, is revealed by ion beam polishing at an angle, forming a wedge-like profile of the substrate/interlayer/DLC system. The chemical binding and composition of the interlayer/interface is determined by Auger electron spectroscopy (AES), and the susceptibility of the different interfaces to carbide formation and oxidation is identified. It is shown that pure interlayer/interface materials can be obtained for the model Co interlayer. On the other hand, for more reactive materials such as Si, Ti and Cr, the formation of new interface phases was observed. Journal Pre-proof This document is the accepted manuscript version of the following article: Ilic, E., Pardo, A., Suter, T., Mischler, S., Schmutz, P., & Hauert, R. (2019). A methodology for characterizing the electrochemical stability of DLC coated interlayers and interfaces. Surface and Coatings Technology, 375, 402-413. https:// doi.org/10.1016/j.surfcoat.2019.07.055 This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/