Influence of metallurgical states on the corrosion behaviour of Al–Zn PVD coatings in saline solution

• This article points out our research on sacrificial Al–Zn PVD coatings.
• The corrosion behaviour of the coatings change at a specific zinc value.
• The reactivity of the coatings increases with zinc content.
• The samples with a uniform corrosion provide a good sacrificial protection to steel.

The objective of this study is to define the corrosion behaviour of different Al–Zn coatings, deposited by magnetron sputtering. The coatings exhibiting the best corrosion resistance are then characterised during long immersion tests in neutral 5 wt.% NaCl solution.The results show that the corrosion behaviour is strongly dependent on the zinc content. The evolution of the degradation mechanism is also related to the microstructure of the alloys. These alloys present very interesting properties for steel protection. Nevertheless, the zinc content has to be well defined in order to avoid a high dissolution of the coating.