The Effect of Flow Structure on Corrosion: Circling-Foil Studies on 90/10 Copper-Nickel, and Hydrodynamic Modeling of the Erosion-Corrosion Process

Abstract

The effects of turbulent flow on the corrosion behavior of 90/10 Cu-Ni were studied experimentally in synthetic seawater electrolyte, using a circling foil apparatus at relative velocities up to about 6 m/sec. The flow field at the specimen surface was characterized by anemometric methods. Corrosion rates were determined by direct weight loss and by several electrochemical methods, including the linear polarization method and from Tafel plots; also zero resistance ammeter measurements were made on galvanic couples. Consideration was given to the question of the appropriate analytical approach to velocity (fluid flow) effects on corrosion processes. The contribution of convective diffusion is considered dominant over the velocity range studied, and the rate of eddy diffusivity (fine flow structure effects on mass transport) is described. The separate electrochemical and mechanical influences of high-intensity turbulent flows are considered.