Effect of 1-pyrrolidine dithiocarbamate on the galvanic coupling resistance of intermetallics – Aluminum matrix during corrosion of AA 2024-T3 in a dilute NaCl

• PDTC interacts with Cu-rich particles.
• PDTC preferentially adsorbs on Al–Cu–Mg particles.
• Oxygen diffusion to cathodic sites is hemispherical.
• PDTC decreases the cathodic sites area leading to a high coupling resistance.
• An electrical circuit containing the galvanic coupling resistance is proposed.

1-pyrrolidine dithiocarbamate (PDTC) effect on galvanic coupling resistance of AA 2024-T3 alloy in 0.2 g L−1 NaCl was evaluated by different electrochemical/gravimetric methods and surface analysis. The results obtained from polarization curves and electrochemical quartz crystal microbalance measurements showed that PDTC forms an adsorbed film on the Cu-rich particles, likely through a CuI–PDTC complex. At high concentrations, PDTC significantly decreases the alloy reactivity thereby providing a marked corrosion protection. SEM–EDX analysis showed that PDTC adsorbs preferentially on the Al–Cu–Mg particles. Electrochemical impedance spectroscopy measurements corroborate these results and show furthermore that PDTC addition increases the galvanic coupling resistance.