In a recent article Dévay et al1 described a technique to measure the maximum galvanic corrosion current between two dissimilar electrodes using a potentiostat. The primary purpose of the potentiostat is to provide a “zero impedance” instrument to measure the external current. We described here a simpler and more economic alternative to the measurement of the short circuit galvanic current. The principle is to use an operational amplifier directly as a zero impedance ammeter.
The circuit is shown in Figure 1. One of the electrodes of the couple is grounded. The other is connected to the negative input of a high-gain operational amplifier Al. The output of this amplifier is given by
where Vs is the voltage, referred to ground, of the electrode and G is the open loop gain, >106. Thus, values of Vo up to the...
