New multiple specimen potentiostatic system

Abstract

A new potentiostatic system has been designed which is capable of controlling and monitoring for large periods of time a large number of specimen electrodes at many different set potentials, all within a single test tank or process stream. The advantages of the new system are illustrated by comparing block diagrams of a version which contains two potentiostats with those of the system which would have to be used to achieve the same results with the standard potentiostat configuration. In order to assess the performance of the new system, a prototype was built with two potentiostats that were independent except for their sharing of a common auxiliary electrode within a single test cell. An experiment was conducted in which one working electrode made from AISI430 stainless steel was subjected to the potentiostatic anodic polarisation scan outlined in ASTM G5–82 while the other identical working electrode was held at a constant potential that was 200 mV more negative than its corrosion potential. The current density at each potential for the electrode subjected to the anodic polarisation scan fell within the range of acceptable values presented in ASTM G5–82. The gradual decrease of current density observed at the electrode held at constant potential was not affected by interrupting the current flowing through the other electrode at the end of its scan. These observations indicate that there was no measurable interaction between the two working electrodes. Thus, the validity of the concept leading to the design of the new system has been demonstrated.