METHODS OF APPLICATION 1-21 2. IMMERSION This is a painting method by which the work is immersed in a paint bath. This is done either by dipping or electrodeposition. (1) DIPPING As illustrated below, the work is dipped in paint completely. Dipping ensures a number of merits. It can paint works of complex shapes and of various sizes, from extra large to small, with minimal paint loss. But the coat thickness varies substantially between the top and bottom parts of the work and air pockets are formed in closed sections. Remove.d r.
Removed D Paint Drips II Dipped PRINCIPLE OF DIPPING (2) ElECTRO DEPOSITION PAINTING This method is known as * ED painting, in which electricity is applied to a bath containing the work and paint. The coat is formed by adhesion of the paint to the work through a process called electrocrystallization. In addition to all the merits of the dipping method, electrodeposition ensures an even coat thickness and is relatively free of such defects as dripping and running because the coat thickness can be con- trolled accurately by regulating the electric current. It also ensures coating in closed sections.
This method is suited for an automatic process although it requires a large investment in equipment. * ED .... ELECTRO DEPOSITION _o_- _o~ :o_ :o- :o- - _o: 0- _o: -o.:: _o: CD Resin and pigment particles electrically charged in a solution ~ When the work is immersed in the bath and a direct current is applied between the work and the bath, those particles start to move toward the object (this movement is called electrophoresis). (3) Resin and pigment particles reaching the work lose their electrical charges and form a coat (this process is called electrocrystallization). @ The paint is dehydrated naturally and forms a continuous film (this process is called electrical infiltration).
PRINCIPLE OF ELECTRODEPOSITION PAINTING -23-