On the fluid mechanics of electrochemical coating and spray painting

Abstract: Finite-volume methods have been used for modeling of fluidflows involved in forced convection electrochemical coating androtating spray painting systems. Electrodeposition on a singlecircular cylinder under forced convection for Reynolds numbers10 and 200 was simulated. Comparisons with earlier numericaland theoretical results are presented and it is shown that theunsteady wake that appears for Reynolds numbers greater than 50affects the mass transfer from the surface of the cylinder onlyin an average sense. This result is compared with a heattransfer case, where unsteadiness is much more manifest. Theeffect of application of circulation movement around thecylinder surface was considered, showing that the use ofoptimal values for circulation can create a recirculation zonearound the cylinder and result in a remarkable improvement ofthe deposit uniformity. The magnetoelectrolysis researchdiscipline is presented with focus on magnetic fields uses onmass transfer processes. A classification of the governingdimensionless parameters that control the phenomena isproposed. Application of magnetoelectrolysis on electroplatingprocesses is done for the first time. It is found that the useof an alternating magnetically induced force around thecylinder can result in interesting improvement of quality andproductivity. Application of numerical methods is also studiedin another field of the surface finishing industry, thepainting atomizers. A critical situation of "reverse flow" isanalyzed. Different parameters of this phenomenon are studiedand suggestions for atomizers design are given and tested.Keywords:mass transfer, electrochemical coating, iontransport, forced convection, diffusion, magnetoelectrolysis,electrolyte, limiting current, numerical simulation,finite-volume methods, paint atomization, Coanda effect.