CORROSION AND DISSOLUTION RATES OF SOME METALS MEASURED BY SIMULTANEOUS CORROSION MEASUREMENTS BY TITRATION (CMT) AND ELECTROCHEMICAL MEASUREMENTS (EC)

摘要

Recording of Corrosion Measurements by Titration (CMT) and Electrochemical measurements (EC) in the same experiment has proved useful and enabled detection of effects such as non-electrochemical metal dissolution. This procedure supplemented by chemical analysis of the amount of metal dissolved in an experiment has been used for investigation of the chromium electrode. In acid sulphate and chloride solutions two cathodic and apparently three anodic reaction regions aree found. In the lowest anodic region, near to -500 mV(she), electrochemical dissolution of a monovalent chromium species, quickly being oxidised to divalent chromium in solution, was confirmed. Non-electrochemical dissolution of the metal at lower cathodic potentials was proved. An unexpected detection of dissolution of gold after prolonged cathodic polarization was confirmed by chemical analysis. Though some experiments were made at lower pH values, the limit of reliable CMT measurements was found to be around pH=2.0.