Studies on the influence of chloride ion and pH on the electrochemical behaviour of aluminium alloys 8090 and 2014

The influence of chloride ion concentration and pH (2.0, 6.0 and 11.0) on the corrosion behaviour of 8090 (Al-Li-Cu-Mg-Zr) and 2014 (Al-4.4%Cu) alloys has been studied in NaCl solution using a potentiodynamic polarization technique. The corrosion rate for both the alloys was high at pH values of 2.0 and 11.0 as compared to that at pH 6.0, and the rate increased in chloride ion concentration at all pH levels. A similar result was found for the passive current density. Increase in pH changed the slope of the cathodic polarization curve by changing the cathodic reaction. Increasing the chloride ion concentration decreased the cathodic reaction rate. On the other hand, the anodic reaction rate increased with increase in chloride ion concentration. The open circuit corrosion potential and the pitting potential shifted in the active (negative) direction with increasing pH and chloride ion concentration. The i p values for 8090-T851 were slightly lower than those for 2014-T6.