Process Stages of CDC-Separation

In  cathodic dip coating (CDC)  a series of individual electro-mechanical steps occur within the coating process:

Firstly, in the scope of electrolysis water is divided into its components hydrogen and oxygen by applying direct current. This means that the object to be coated is used as a cathode. The water is broken down electrolytically and an alkaline barrier layer (hydroxyl layer) forms on the cathode. Under the influence of the electric field the dispersed, positively-charged particles of the paint (micelles) migrate to the cathode (negative pole). This paint migration is known as electrophoresis. In the following stage – coagulation – the paint particles are neutralized due to the change in pH value in the alkaline barrier layer on the cathode and deposited onto the object. The water is displayed from the film, a compact wet film is formed (electro-osmosis). The film formation increases electrical resistance on the object and film formation ultimately slows.