Many applications requiring light weight, good strength, and corrosion resistance use 5xxx and 6xxx series aluminium alloys. One such application is cooling channels in ASML cooling systems, where AA5083 and AA6082 Cu-free alloys are employed to carry the flow of semiconductor-grade ultra-pure water. Due to several reasons, even under ultra-pure water conditions, corrosion of aluminium channels is unavoidable. Localised corrosion due to the galvanic coupling formed between the intermetallic phase and the aluminium matrix is known to be the reason behind corrosion initiation and propagation. However, the behaviour and role of different types of intermetallic phases are not completely understood.

This study attempts to better understand the role of intermetallic phases in the corrosion initiation of AA5083 and AA6082 alloys. For this purpose, localised techniques are employed to evaluate the electrochemical properties of intermetallic phases and to study the activity of the sample surface through SKPFM and in-situ SECM experiments, respectively. The study also performs potentiodynamic polarisation tests to understand the overall corrosion performance of the alloys in ultra-pure water, an artificial mixture of impure water, and a 0.1 M NaCl solution.

In addition, regarding the electrochemical behaviour of the intermetallic phases, it is found that the alloy composition and the surface distribution of the intermetallic phases also contribute to and have a significant effect on localised corrosion initiation. The results of the localised techniques carried out using a 0.1 M NaCl solution agree with the observations obtained for ultra-pure water and the artificial mixture conditions.