Predicting the Distribution of Electroplated Coatings Using ANSYS
The performance of control valve internal parts can be greatly enhanced by coating critical surfaces with a layer of chromium. The chromium is typically deposited by an electrolytic process in which the part to be coated is immersed in an electrolyte containing chromium ions. A direct current flow is then maintained between an immersed anode and the work part, which acts as the cathode. The distribution of the resulting chrome deposit is influenced by a multitude of factors including the geometry of the part to be coated and of the supporting fixture. The electric field analysis capability of ANSYS provides a method of predicting the distribution of chrome deposits. In addition to the work part and supporting fixture, the model must also include the anode as well as the electrolyte. Material property inputs for the electrolyte must be calibrated to accurately simulate the process of interest. The deposit thickness over the critical surfaces is then determined from the relationship between surface current density and rate of deposition. Once developed and calibrated, the model can be used to optimize the distribution of the chrome deposit. The above technique is illustrated by an example in which ANSYS is used to predict the distribution of the chrome deposited on the surface of a ball valve control element.