UNCORRECTED PROOF 1 2 Tribocorrosion behaviour of Zro x n y thin films for decorative applications 3 S.C. Ferreira a , E. Ariza a , L.A. Rocha a, ⁎ , J.R. Gomes a , P. Carvalho b , F. Vaz b , A.C. Fernandes b , 4 L. Rebouta b , L. Cunha b , E. Alves c , Ph. Goudeau d , J.P. Rivière d 5 a Universidade do Minho, Dept. Eng. Mecânica, Azurém, 4800-058 Guimarães, Portugal 6 b Universidade do Minho, Dept. Física, Azurém, 4800-058 Guimarães, Portugal 7 c ITN, Departamento de Física, E.N.10, 2685 Sacavém, Portugal 8 d Laboratoire de Métallurgie Physique, Université de Poitiers, 86960 Futuroscope, France 9 Abstract 10 The aim of this work is the investigation of the tribocorrosion behaviour of single layered zirconium oxynitride, ZrO x N y , thin films in 11 reciprocating sliding and immersed in an artificial sweat solution at room temperature. During the wear tests samples were kept under 12 potentiostatic control and the corrosion current were monitored. Also, Electrochemical Impedance Spectroscopy (EIS) tests were performed before 13 and after sliding in order to evaluate, in detail, the modification of the protective character of the coating caused by the joint action of wear and 14 corrosion. The modifications of the coating structure and microstructure and/or chemical composition originated by the variation of the deposition 15 parameters were also evaluated and correlated with the corrosion mechanisms occurring in each system. 16 © 2005 Elsevier B.V. All rights reserved. 17 18 Keywords: Tribocorrosion; Decorative films; Zirconium; EIS 19 20 1. Introduction 21 Vacuum coating techniques, especially Physical Vapour 22 Deposition (PVD) of decorative layers has been industrially 23 used for more than 15 years. Decorative hard coatings have first 24 been introduced on small decorative parts such as watches, 25 writing instruments and spectacles frames. In the last few years, 26 there has been considerable interest in the production of metallic 27 oxynitride thin films, MeO x N y (Me = early transition metal) [1– 28 6], since the presence of oxygen in nitride compounds leads to 29 unexpected and promising functional range of materials. The 30 presence of oxygen allows the tailoring of film properties 31 between those of metallic nitrides, MN y , and those of the 32 correspondent insulating oxides, MO x . Tuning the metallic/ 33 covalent and ionic bonding characteristics allows one to tune 34 the mechanical, electrical, chemical and optical properties of 35 materials, including colour. Recent publications suggest that the 36 performance of these oxynitrides depends not only on the 37 deposition method but also on both the concentration and 38 distribution of the nitrogen atoms incorporated into the matrix 39 [1–9]. 40 Decorative thin films may be exposed to aggressive chemical 41 environments, such as human sweat, while, at the same time, 42 they can also be subjected to wear due to hand touch or cleaning 43 procedures. The degradation of the materials by mechanical 44 (wear), chemical and electrochemical processes is defined as 45 tribocorrosion [10–13]. The interactions of chemical and 46 mechanical parameters on the tribocorrosion behaviour cannot 47 be always predicted on the basis of separate wear and corrosion 48 experiments. In fact, wear accelerated corrosion arises from the 49 fact that an asperity rubbing on a surface produces a clean track 50 which is usually more sensitive to corrosion than the same 51 surface in the absence of rubbing conditions, thus contributing 52 to removal of material [14,15]. Also, the presence of pores in the 53 film, among other chemical, electrochemical, physical and 54 mechanical factors, can lead to the attack of the substrate 55 contributing to the material degradation in the tribological 56 contact [16,17]. Many aspects of the tribocorrosion mechanisms 57 acting on thin films are not yet fully understood, partly due to 58 the complexity of the processes involved. 59 The main purpose of this work consists on the study of the 60 corrosion behaviour and degradation mechanisms of decorative Surface & Coatings Technology xx (2005) xxx – xxx + MODEL SCT-11935; No of Pages 6 www.elsevier.com/locate/surfcoat ⁎ Corresponding author. Tel.: +351 253 510 231; fax: +351 253 516 007. E-mail address: lrocha@dem.uminho.pt (L.A. Rocha). 0257-8972/$ - see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2005.11.083 ARTICLE IN PRESS