The ability of cathodic dip-spin coating (CDC) to also reach difficult to access areas of the surface to be coated with the coat particles, thus protecting against corrosion, is known as engulfing.
How does this engulfing work? In the application process direct current is established between electrode and object. The current initially seeks out the path of least resistance. This means: the exterior surfaces are coated first – these are closest to the electrode. The exterior coating leads to increased electrical resistance. The current consequently seeks a path with low resistance – even if this may be longer. This enables even difficult to access parts to be coated. This process is repeated continuously, until electrical resistance is too high and the minimum current density required for coating can no longer be achieved. The result is an even coat thickness on the object to be coated – outside and inside – and therefore effective corrosion protection.