Potentiodynamic polarisation experiment

The time factor in stepwise potentiostatic or potentiodynamic polarisation experiments is very important, because large differences can be caused by changes in the scanning rate. Since the steady state depends on the particular system and conditions of exposure, no set rule exists for the magnitude or frequency of potential changes. Chatfield etal. have studied the Ni/H2S04 system and have shown how becomes more passive with increase in sweep rate. 

The solid lines Cl and A1 represent the relationship of current (i) vs. potential ( ) for a metal as measured by potentiodynamic polarisation experiments. Cl represents a cathodic polarisation and A1 represents an anodic polarisation. The open-circuit potential (OCP) is the unpolarised potential where the rate of cathodic surface reactions balances the rate of anodic surface reactions (i.e. where current is on average zero). By applying a 100 mV potential between two identical electrodes, one is polarised to be anodic and the other cathodic. The current flow between the electrodes... 

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