THE IMPINGING JET ELECTRODE - MEASUREMENT OF THE HYDRODYNAMIC CONSTANT AND ITS USE FOR EVALUATING FILM PERSISTENCY

The impinging jet system involves either a disk electrode or a ring electrode immersed in electrolyte and subjected to an axis-symmetric impinging jet of the same electrolyte. Ring-electrode experiments were used to determine the value of the hydrodynamic constant and to identify the constraints on cell design such that the electrode surface is situated within the stagnation region (that is, where the shear stress is a linear function of radial position). The geometric constraints obtained were tighter than previously reported results. The system was also employed to evaluate inhibitor film persistency under high-speed fluid flow. With the proper experimental desing, the critical shear for removal of a protective film can be obtained by measuring the profile of an electrode subjected to a given electrolyte jet velocity. This technique is illustrated for evaluation of single-compound inhibitors in acidic chloride solutions.