INVESTIGATING THE CORROSION BEHAVIOR OF NANO STRUCTURED COPPER STRIP PRODUCED BY ACCUMULATIVE ROLL BONDING (ARB) PROCESS IN ACIDIC CHLORIDE ENVIRONMENT

In this research accumulative roll bonding process as sever plastic deformation process was applied up to 8 cycles to produce the ultrafine grain copper. Microstructure of cycle 1, cycle 4 and cycle 8 investigated by TEM images. By analyzing TEM images the grain size measured below 100 nm in cycle 8 and it was with an average grain size of 200 nm. Corrosion resistance of rolled copper strips in comparing with unrolled copper strip was investigated in acidic (pH=2) 3.5 wt. % NaCl solution. Potentiodynamic polarization and EIS tests used for corrosion resistance investigations. The corrosion morphologies analyzed by FE-SEM microscopy after polarization test and immersion for 40 hours. Results show that the corrosion resistance decreased up to cycle 2 and increased after rolled for forth time. The corrosion degradation was more intergranular in cycle 2 and unrolled counterpart. It was more uniform rather than intergranular type in cycle 8. Corrosion current density in unrolled sample (2.55 ?Acm-2) was about two times of that in cycle 8 (1.45 ?Acm-2). The higher corrosion rate in cycle 2 in comparison with others was attributed to unstable microstructure and increase in dislocation density whereas the uniform corrosion in cycle 8 was due to stable UFG formation.