New Theories for Erosion-Corrosion
Final rept. 1 Oct 93-30 Sep 98
FLORIDA UNIV GAINESVILLE DEPT OF CHEMICAL ENGINEERING
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The erosion-corrosion of copper and copper-nickel alloys in synthetic seawater was investigated using an impinging jet. Video microscopy, corrosion potential monitoring, and impedance spectroscopy were used to investigate the state of the system and the reactivity of the electrode surface. Shear-induced removal of salt films was observed and found to be associated with significant increases in surface reactivity. Direct shear-induced removal of oxide films, however, was not observed. Nevertheless, the protective oxide layer showed sensitivity in passively aerated seawater to large fluid velocities and to small perturbations in potential. The films were stable under all conditions tested in continuously aerated seawater. The present work supports the argument that localized corrosion of copper alloys is caused by galvanic coupling between different regions of a metal coupon. Thus, cathodic protection may be used to prevent such corrosion. A modeling and experimental study was conducted to show the conditions under which non-uniform current distributions influence the impedance response of a disk electrode. Measurement model tools were developed to identify the stochastic and experimental bias errors. This information was used to filter data, design experiments, and assess the validity of regression assumptions and the confidence intervals of the resulting parameters.
- Properties of Metals and Alloys
- Physical Chemistry