Charge kinetics I suppose. Smaller sample will probably have low charge gradient which would translate to even corrosion. The output signal will most likely also attain a steady state quite early in the experiment.
Thank you Matthew for your answer. Now that the charge gradient is proportional to the surface is something we should minimize to attain more accurate corrosion rate measurements.
I'm not aware of any recommendation to minimize the surface area of the electrode during an electrochemical corrosion test. Can anyone refer me to this recommendation?