Corrosion Behavior of Al-based PVD Multilayer Sacrificial Coatings Sébastien Touzain 1 , Juan Creus 1 , Andréa Perez 1 , Frédéric Sanchette 2 and Alain Billard 2 1. Laboratoire des Sciences de l’Ingénieur pour l’Environnement, FRE 3474 CNRS UFR Sciences, Université de La Rochelle, Avenue Michel Crépeau, 17042 La Rochelle (France) 2. LERMPS / UTBM, Site de Montbéliard, 90010 Belfort cedex, FRANCE sebastien.touzain@univ-lr.fr Introduction Aluminum-based coatings deposited by Physical Vapor Deposition (PVD) are known as an alternative friendly solution to pollutant corrosion protection systems. However, aluminum- based coatings present a localized corrosion associated to a pitting corrosion [1] and do not present good mechanical properties. In order to have a slow dissolution of the coating, a uniform corrosion is preferable [2-4]. This can be obtained by incorporating some elements which change the electrochemical behavior of the aluminum-based coating (e.g. Zn, Y, Gd or Mg). Moreover, a multilayer structure including hardener elements (Mo, Mn) can also be proposed as a way to improve mechanical resistance. This paper is dedicated to the description of the mechanical and electrochemical properties of different multilayer coatings based on Al-Mn and Al-Mo alloys. The influence of the period evolution is discussed and the results deduced from the different architectures are compared in order to evaluate the best configuration. Experimental Multilayer coatings have been deposited by magnetron sputtering onto glass slides and steel substrates. The deposition parameters are constant except for the deposition time of each alloy. Al-Mo and Al-Mn alloys at respectively 18 and 7 or 9 at.% were selected for their mechanical properties, whereas Al-Mg and Al-Y at respectively 11-15 and 18 were selected for their sacrificial character. Five multilayer configurations: Al-Mn/Al-Mg, Al-Mo/Al-Mg, Al-Mn/Al-Y, Al-Mn/Al-Gd and Al-Mo/Al-Y were investigated, the last layer in contact with the aggressive environment is always the alloys selected for their sacrificial character. The period was changed between 15 to 120 nm in order to study its effect on the multilayer properties. The argon pressure is 20 sccm and all the coatings have a total thickness of 5 μm. The coating morphology is observed using a scanning electron microscope (SEM). Cross- section observations were performed in order to evaluate the interface between the inner layers, and TEM observations were necessary for period close to 15 nm. Microstructure was also studied through X-ray diffraction (XRD). Energy Dispersive X-ray Spectroscopy (EDS) analysis were used in order to measure the surface composition of the coatings. The hardness of the coatings was evaluated with a Nano Hardness Tester (CSM instruments), and the value given is an average of ten measures. Electrochemical investigations were realized in an aerated and stirred NaCl 5 wt.% solution with pH adjusted to 7 at (25.0 ± 0.1)°C. The electrochemical experiments were carried out using a conventional three electrode glass cell with samples as working electrode, connected to a Perkin Elmer EG&G 273A potentiostat. The potential is referred to a saturated calomel electrode (SCE) and the counter electrode is a large platinum grid. The corrosion behaviors of coatings deposited onto glass slide were evaluated through potentiodynamic experiments after one hour of immersion and through immersion test of 48h in saline solution. The potentiodynamic polarization curves were plotted after an initial potential stabilization of 1 h from -150 mV (vs. Open Circuit Potential) in the cathodic side, up to a potential corresponding to a current density threshold of 100μA/cm² in the anodic side, using a sweep rate of 0.2 mV/s. The current density threshold is used to limit the pitting degradation. The corrosion potential Ecorr and current density jcorr were estimated by using Tafel extrapolation.