Influence of the Alloying Elements on Uniform and Pitting Corrosion Events Induced by SCN- Anions on Al-6061 and Al-Cu Alloys Surfaces

The electrochemical and corrosion behaviour of Al-6061, Al-4.5%Cu and Al-7.5%Cu alloys were studied in 0.50 M KSCN solution at 25 °C. Open-circuit potential, Tafel polarization and ICP-AES measurements were used to study the uniform corrosion process on the surfaces of the tested alloys. Cyclic polarization measurements were employed for pitting corrosion studies. Obtained results were compared with pure Al. Alloyed copper was found to enhance uniform corrosion of Al in SCN- solutions to an extent depending on its content in the Al sample. The pitting potential (Epit) and the repassivation potential (Erp) increased with an increase in the alloyed copper content. Thus alloyed copper suppressed pit nucleation and propagation. The effect of temperature was also studied and the apparent activation energies were determined as a function of alloy composition. Among the investigated materials, Al-6061 alloy has the highest corrosion resistance towards uniform and pitting corrosion processes in KSCN solutions.