Determining the appropriate scan rate to perform cyclic polarization test on the steel bars in concrete

Cyclic potentiodynamic polarization technique is a relatively non-destructive measurement that can provide information about the corrosion rate, corrosion potential, susceptibility to pitting corrosion of the metal and concentration limitation of the electrolyte in the system. The technique is built on the idea that predictions of the behavior of a metal in an environment can be made by forcing the material from its steady state condition and monitoring how it responds to the force as the force is removed at a constant rate and the system is reversed to its steady state condition. Applied potential is the force and is raised at a continuous, often slow, rate by using potentiostat. This rate is called polarization scan rate and is an experimental parameter. It is very important to choose the most appropriate scan rate, specifically in the complicated system such as reinforced concrete; otherwise the result does not reflect the corrosion behavior and the result could be an incorrect polarization scan and an incorrect prediction from it. In this paper, the effect of different scan rates on the apparent corrosion behavior is shown and a method to choose the appropriate rate is discussed.