Abstract: A phosphate bath control system and method is provided that tracks the set points of one or more of the major process variables of the phosphate bath independently of variations in the production conditions. A detector determines the current values of Zinc, Manganese and Total Acid provides data to a controller which exponentially filters the data and processes the filtered data in accordance with fuzzy logic rules. The controller periodically updates the flow rate of one or more pumps that control the flow of liquid concentrates to the bath in order to maintain a desired concentration of the various constituents of the bath. Control of an accelerator is provided by incorporating in the controller an additional algorithm for indirect estimation of the accelerator concentration based on a math model which represents the material balance of the accelerator in the bath.