General aspects related to the corrosion of 6xxx series aluminium alloys: Exploring the influence of Mg/Si ratio and Cu

• A comprehensive study was conducted upon Al–Mg–Si alloys with differing Mg/Si ratio and Cu content.
• Corrosion investigations included naturally aged, under-, peak- and over-aged conditions.
• Ageing conditions and solute content all had an influence on the corrosion (and morphology).
• Cu content was dominant over the Mg/Si ratio in terms of corrosion response.

Specially prepared 6xxx series aluminium alloys (Al–Mg–Si) with different Mg/Si ratios and Cu contents were investigated in the naturally aged, under-aged, peak-aged and over-aged conditions. Potentiodynamic polarisation and immersion testing in 0.1 M NaCl were used to investigate the corrosion behaviour of such alloys in a general sense. Results reveal a significant dependence of the corrosion rate and morphology on the ageing conditions and solute content. Whilst contributing to broader understanding of 6xxx alloy corrosion, we note that corrosion rate is lowest in the naturally aged condition and is principally influenced by Cu and subsequently by the Mg/Si ratio.