IR Drop

Definition - What does IR Drop mean?

IR drop refers to a voltage drop that appears at the resistive component of any impedance. IR drop is the electrical potential difference between the two ends of a conducting phase during a current flow. This voltage drop across any resistance is the product of current (I) passing through resistance and resistance value (R).

IR drop has a great influence on electrochemical measurements, and their effects should be considered during the interpretation of electrochemical data.

IR drop is also known as "ohmic potential drop" in electrochemistry.

Corrosionpedia explains IR Drop

IR drop is a potential drop due to solution resistance. It is the difference in potential required to move ions through the solution. It results from the electric current flow in ionic electrolytes like dilute acids, saltwater, etc. IR drop (ohmic drop) is an unwanted quality and it must be removed to obtain an accurate potential measurement.

IR drop has produced some unwanted results in measurements. For example, in cyclic voltammetry, IR drop primarily causes a shift in peak potential, decrease in the magnitude of current, and increase in peak separation. These effects will become more prominent as the scan rate is enhanced following the increase of current.

IR drop depends on the following factors:

  • The current and potential distribution in the electrolyte – changing the size or shape of the working electrode will change the shape of the equipotential lines.
  • The position of the reference electrode with respect to the working electrode.
  • The conductivity of the electrolyte solution – the lower the conductivity of the electrolyte, the higher the IR drop.

The following measures will be needed to minimize the IR drop:

  • Using a three-electrode system
  • Adding a high concentration of fully dissociated electrolytes to the solution
  • Placing the reference electrode tip within close proximity of the working electrode surface
  • Using low scan rates that will minimize the current
  • Decreasing the electrode surface area
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