Using Electrochemical Noise to Obtain More Information From Conventional Corrosion Test Methods

摘要

Within corrosion research, the analysis of electrochemical noise offers a simple, sensitive and virtually non-destructive measuring technique for assessment of the corrosion susceptibility of metallic materials and for the investigation of corrosion processes. The present status of knowledge concerning noise diagnostics in corrosion processes permits the application of this method not only to experimental tasks in the laboratory, but also to special problems in the context of practical corrosion monitoring. Furthermore, specific advantages of the technique enable its use to an increasing extent in supporting or improving conventional corrosion testing. The advantages here include obtaining additional information and shortening testing times (together with associated savings in resources such as manpower, energy, chemical reagents, etc.), thus resulting in state-of-the art corrosion testing. In this paper, it is shown, with the aid of three examples taken from the routine work of a corrosion laboratory, how conventional testing methods and investigation procedures can be enriched by the application of electrochemical noise techniques. In the first example, current noise measurement using a zero-resistance ammeter is used to investigate the development of corrosion over time during salt-spray testing, thus making assessment of the test samples better and more quantifiable. During potentiostatic experiments, in the second example, additional noise diagnostics permits conclusions as to critical regions of potential and chloride concentration, as well as the effect of inhibitors, to be drawn within the shortest possible testing period. Detection of the initiation processes of corrosion (e.g. incipient pitting) is not possible simply using the conventional method of total current measurement. In the third example, the testing requirements for the determination of critical pitting temperatures can be reduced considerably and, in particular, the evaluation of the noise signals can be carried out so as to eliminate