A workpiece coating (esp. chemical or electroless plating) process involves determining the capability of a material to contaminate a chemical coating bath by (a) dissolving the material in a test bath with components of known purity; (b) placing the test bath in a voltammetric cell (20) with at least three electrodes (23-25); (c) applying d.c. voltage to two of the electrodes (23,24) at a voltage increase rate creating an anodic current at the surface of the third electrode (25); (d) measuring the resulting anodic current as a function of the applied voltage to produce a current profile; and (e) comparing the profile with a second profile obtained from a second test bath with components of known purity.
