Edge coverage of cataphoretic epoxy primer on steel substrate was optimised with three different functional additives: pigment paste, microgel MG 1 and microgel MG 2. The binder to pigment paste ratio was 4/1 and with addition of pigment paste it was changed to 3/1. Various contents of each microgel separately were incorporated into the electrocoating bath: 3, 6, 8 and 10 wt. %. Gloss, elasticity by Erichsen, bending, impact resistance and adhesion were used to study the effect of additives on mechanical properties of cured coating. Salt spray test and AC-DC-AC method were used to study improved anti-corrosion properties of cured coating on the edges. A correlation between salt spray test and AC-DC-AC method was determined. The correlation error for samples with binder to pigment ratio 4/1 is 10.8% when MG 1 or MG 2 is added. The correlation error for samples with binder to pigment ratio 3/1 is 6.3% when MG 1 or MG 2 is added. The salt spray test and AC-DC-AC method proved that samples with binder to pigment paste ratio 3/1 and addition of 8 wt. % MG and or MG 2 show improved anti-corrosion properties on the edge.
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