Corrosion and mechanical behavior of mono- and multi-layer Al-based PVD coatings in NaCl solution

摘要

Aluminum-based coatings deposited by dc magnetron sputtering Physical Vapor Deposition (PVD) are known as an alternative friendly solution to pollutant corrosion protection systems. In order to improve the sacrificial effect with regards to steel, Zn, Y or Mg can be added to the PVD coating formulation. Moreover, a multilayer structure including hardener elements (Mo, Mn) can also be proposed as a way to improve mechanical resistance. The first objective of this work is to study different Al-Zn, Al-Y and Al-Mg compositions and their corrosion behavior for an immersion test in NaCl 5 wt.% solution. The results show that depending on the alloying element content, pitting or uniform corrosion behaviors are obtained. For the samples showing a uniform corrosion, the immersion test reveals that they provide a good protection to steel during the immersion period. Secondly, multilayer PVD systems were designed in order to associate good corrosion performances with better mechanical properties: Al-Zn/Al-Mo and Al-Y/Al-Mn were tested. The results are discussed in terms of microstructure, corrosion potential and mechanical resistance.