The iR drop - well-known but often underestimated in electrochemical polarization measurements and corrosion testing

Abstract

At first sight the problem of the iR drop and its compensation in electrochemical polarization measurements seems to have only minor significance, but it has actually troubled electrochemists and corrosion scientists for more than a hundred years. For reducing the iR drop in the electrochemical cell, its computation, experimental determination and numerical or automatic electronic compensation numerous scientific and experimental work has been carried out and appropriate suggestions were submitted. These efforts led to commercially available potentiostats with sophisticated facilities for automatic iR compensation. Nevertheless, to date these possibilities have been utilized with a certain hesitancy. Many users underestimate the iR drop, regarding it often merely as a marginal problem, which only has to be taken into account in experiments with very high currents or extremely low conductivity of the electrolyte. Furthermore, there are also doubts and prejudices regarding modern methods of iR compensation, resulting from previous unpleasant experiences or reports on failed experiments with inappropriate equipment or imperfect methods. Reduction or automatic compensation of the iR drop is necessary more frequently than generally assumed and also in most cases possible. On the other hand the application of the different methods is still not completely uncomplicated and requires special experimental experience and care. The aim of the present work is it therefore to give a comprehensive retrospective overview of the ohmic drop problem and the relevant activities to overcome it.

Repassivation behavior of 316L stainless steel in borate buffer solution: Kinetics analysis of anodic dissolution and film formation

“…Because of the low conductivity of the borate buffer solution, un-compensated solution resistance needs to be taken into account during electrochemical experiments. A positive feedback technique [30] is used for automatic IR compensation during tests due to the high sampling rate, which is discussed in Section 3.1. After abrading tests, the samples are taken out and saved in a vacuum sealed container, and examined by optical microscope and XPS.…”

Investigation of the Oxygen Reduction Activity on Silver – A Rotating Disc Electrode Study

“…Prior to each measurement the solution resistance (R u ) [17] from the working electrode to the Luggin capillary was determined using an AC signal (5 kHz, 5 mV), and thereafter electronically compensated for by a positive feedback scheme. [6] In our setup, the typical R u was around 10 X; however, in some cases values above 20 X were determined, which have a large effect if no compensation scheme is used.…”

Highly Active Mixed-Metal Nanosheet Water Oxidation Catalysts Made by Pulsed-Laser Ablation in Liquids

“…Post-measurement iR drop correction was performed according to Oelßner. 7 We chose to use this method, where we experimentally determined Ru for our nanoparticulate catalysts under the same conditions as all other electrochemical measurements, because automatic iRcorrection is inherently problematic for high-surface-area materials. In detail, the true polarization potential Ep was calculated from the applied potential Ea, the measured current i, and the uncompensated resistance Ru as Ep = Ea − iRu.…”