Ideally, we would like to use a chemical solution that can dissolve the oxide layer and do so uniformly without attacking the base metal (meaning: we want high oxide-to-metal selectivity of the deox chemical). In reality: a) some oxides are sluggish to dissolve, and b) some areas of the part clear oxide sooner and the chemicals begin to etch the metal.
We recognize some chemical solutions are better for a given part and some process conditions are optimal. For example: Microclean EV3 (RDZ-1922) may yield the same %mass loss as Microclean MV (RDZ-1995) but the surface may be more etched with the latter. Or, Microclean EV3 can be used at lower temperature for longer time or at higher temperature for shorter time for same %mass loss but not necessarily identical outcome on the surface.
Then, because the oxide may not dissolve readily in the chemical solution, we employ ultrasonic rinsing in deionized water after the chemical deox step to “shake-off” the oxide. In many cases, the deoxidized surface is “revealed” in the ultrasonic rinse step. And extending the time of the chemical step may lead to overetching the base metal.