Effect of gas sparging on the rate of mass transfer during electropolishing of vertical plates

Rates of electropolishing of vertical copper plates in phosphoric acid using a gas sparged rectangular cell were measured under different conditions of superficial gas (N2) velocity, workpiece height, physical properties of the solution and macroroughness of the surface. The limiting current was found to increase with increasing N2 superficial velocity to the power of 0.24 while increasing workpiece height (L) was found to decrease the limiting current (I) according to the equation, I=aL−0.19. The data were correlated by the equationimageWhere j, Re and Fr are the mass transfer j factor, Reynolds number and Froude number, respectively. Macroroughness was found to increase the limiting current by a modest amount depending on the peak-to-valley height of the roughness elements. The economic importance of using gas sparging in mass transfer controlled metal finishing processes is pointed out.