1-22 BASIC KNOWLEDGE ABOUT PAINTS AND PAINTING Electrodeposition has two types, anionic ED and cationic ED, depending on the electric polarity. In anionic ED, the vehicle body is electrically positive while, in cationic ED, it is electrically negative. ANIONIC ED CATIONIC ED ANIONIC ED AND CATIONIC ED ,------ -------------------------. Cationic ED is preferred in electrodeposition lines for new vehicles because it ensures greater rust preven- tive results. In anionic ED, positive and negative charges are applied to the body and the paint respectively.
Therefore, zinc and iron particles remaining in the zinc phosphate film generated in the preceding process are attracted by negative charges of the paint and are dissolved into the paint. This means a loss in the coat thickness which, in turn, naturally deteriorates its corrosion preventive performance. In cationic ED, metals are not dissolved because the body is charged negatively and the paint positively. This means cationic ED ensures greater corrosion preventive performance. -24-