The Effect of Uncompensated IR-Drop on Polarization Resistance Measurements

Abstract

Abstract A theoretical analysis of the effect of uncompensated IR-drop on polarization resistance (Rp) measurements is given, which shows that it is not the absolute value of the solution plus surface film resistance (RΩ) which determines the error due to IR-drop, but the ratio (RΩ/Rp) An error is possible even in solutions of moderate to high conductivity, if corrosion rates are high. The experimentally determined polarization resistance (Rp) is the sum of the true polarization resistance (Rp) and the ohmic resistance (RΩ). If no corrections are made, polarization resistance values will be determined too high and consequently corrosion rates will be found too low. The effect of uncompensated IR-drop on measured polarization curves is shown. Experimental data with and without IR-drop compensation (“positive feedback”) confirm the theoretical considerations.