Comparison of the intrinsic properties of EBPVD Al–Ti and Al–Mg coatings

► This article points out our research on sacrificial electron beam PVD coatings. ► The hardness of the coatings increases due to the incorporation of Mg or Ti. ► The low Mg content Al–Mg coatings present interesting corrosion properties. Aluminium based alloys were deposited on glass slide substrates by electron-beam evaporative PVD (EBPVD) technique in order to assess to the intrinsic corrosion behaviour in saline solution. Alloying elements (Ti or Mg) were added in order to improve both mechanical and corrosion behaviours of aluminium films. The goal of this study is to develop new alternative sacrificial coatings that could protect steel flat products against corrosion with enhanced mechanical properties in order to limit the seizing sensitivity. Because of the difference in vapour pressures, aluminium and alloying elements were co-evaporated from two separate sources. Mixing of the vapour flux was the most appropriate experimental method to ensure a homogeneous distribution of the alloying element into the aluminium based coating. Different contents of transition metals were examined, and it was noticed that the microstructure evolves from a supersaturated solid solution to an amorphous phase due to the lattice distortions with the incorporation of the alloying elements. Electrochemical behaviour of the EBPVD coatings in saline solution was investigated. It is shown that aluminium can be mechanically reinforced while preserving sacrificial corrosion protection properties. The evolution of the properties was found to be strongly linked to the nature of the incorporated element. A comparison with a previous study on the electrochemical and mechanical behaviour of EBPVD Al–Cr and Al–Gd coatings permitted a comprehensive analysis of the influence of the incorporation of transition metals in aluminium.