Electrochemical noise as a powerful tool for studying corrosion processes

The present work has been addressed to the evaluation of the applicability of electrochemical noise (EN) as a technique to get insights into the mechanism of corrosion processes so as to monitor materials degradation in industrial applications. This technique can be mainly applied to the study of the breakdown of protective films or deposits at the very first moments of the process by measuring current and/or potential fluctuations originating from a two electrode system of the same material. Accordingly, electrochemical noise was applied to study corrosion of specific materials in different testing solutions and experimental conditions. Corrosion morphology was evaluated by optical microscope while the mechanism was studied by visual examination of the EN file as well as by using statistic algorithms relating the electrochemical variables such as average noise current and potential, their standard deviations (delta 1 or delta V) and so on. EN was successfully applied to the study of pitting corrosion of stainless steel, showing possible limitations in differentiating fast pit propagation on a small area from slow propagation of several microscopic pits on a large area

Chemical dechlorination of polychlorinated biphenyl (PCB) in dielectric oils enhanced by ultrasound

This paper reports on the chemical dechlorination of the polychlorinated biphenyls (PCBs) in some dielectric oils via nucleophilic substitution of the chloro atoms by polyethylene alkoxide. The influence of temperature, ultrasounds, PEG and base type were investigated. We observed that dechlorination of PCBs by chemical treatment is effective at moderate operating conditions (90-100 °C) but strongly dependent on the nature of matrix oil. Stirring affects the process yield influencing the homogeneity of two phase system (oil/glycol). Ultrasounds can improve process efficiency by making operating condition less severe