High Speed Selective Electroplating with Impinging Two-Dimensional Slot Jet Flow

The local mass-transfer coefficient on a planar solid surface under an impinging two-dimensional fluid jet was measured for both submerged and unsubmerged systems by an electrochemical technique. Correlations were developed for three regions along the surface: impingement, transition, and wall jet or lateral flow regions. For unsubmerged jets, a theoretical model of the current and potential distribution was developed. It was found that hydrodynamic conditions exert a strong effect on performance at high current densities since flow influences mass transfer and also the shape of the free surface that confines the potential field. The capability of achieving selective reaction in the impingement region was found to improve with increased current density and flow rate. Dimensionless criteria for the upper limit of such improvements were established.