Potentiodynamic Polarization Studies of Glycerin in Platinum Electrodes

<span><p class="TTPAbstract"><span lang="EN-US">A three electrode system was used for the analysis of potentiodynamic polarization studies of glycerin in platinum electrodes. Particular attention was devoted to the estimation of diffusion coefficient of glycerin in platinum electrodes by the use of electrochemical techniques such as the sweep of the potential. Cyclic voltammograms were recorded at different sweep rates (0.01 and 0.07 V·s-1). Randles-Sevcik equation was taken into consideration and a linear relationship was found between </span><span lang="DE">the peak current and the square root of the voltage sweep rate from where the value of diffusion coefficient could be determined. The values of Tafel constants, useful in the understanding of electrochemical reaction kinetics are also reported in the present paper.</span><b><span lang="EN-US"><o:p></o:p></span></b></p>

Evaluation of Corrosion Rates from Polarization Measurements

Polarization measurements within 5 to 20 mV of the corrosion potential offer a powerful method for determining corrosion rates. In this paper, known methods for evaluating the corrosion current from polarization data are critically examined. It is noted that calculated currents are generally in error when the anodic and cathodic Tafel slopes are precisely known, due to non-linearity of the polarization curve. A new result is derived, which allows the corrosion current to be calculated without error if the Tafel slopes are known. Diagrams are presented which show the sensitivity of calculated corrosion rates to errors in estimation of the Tafel constants.

Adaptation of Linear Polarization Techniques for In-Situ Corrosion Measurements in Water Cooled Nuclear Reactor Environments

Application of electrochemical polarization techniques to study corrosion of steels in aqueous environments at 289 C (554 F) and 1000 psi is described. A galvanostatic polarization circuit is discussed which permits determination of polarization parameters in-situ which are free of error due to resistance polarization in high purity water. Extended corrosion tests on plain carbon steel and Type 304 steel over 500 hours have shown that 99.6 percent correspondence can be achieved between electrochemical corrosion data and conventional weight-change techniques. In de-oxygenated conditions, the steady-state corrosion rates of plain carbon steel and Type 304 stainless steel are 0.0015 and 0.0011 mg/cm2hr, respectively in water at 289 C. Cathodic and anodic Tafel constants for these steels under the above conditions have been determined and are shown to be independent of exposure time and corrosion rate.