| 摘要 |
With the use of a lead-free cationic electrodeposition coating composition containing a sulfonium-modified epoxy resin, an amine-modified novolak-type epoxy resin, and a blocked isocyanate curing agent as a binder resin, wherein the content of volatile organic components is 1% by weight or less, the coating liquid conductivity is 1000 to 2500 muS/cm, and the minimum film-forming temperature of the coated layer electrodeposited on an object to be coated is 20 to 35° C., electrodeposition coating is carried out at or above the temperature which is lower by 2° C. than the minimum film-forming temperature and at or below the temperature which is higher by 6° C. than the minimum film-forming temperature. The coating method using the lead-free cationic electrodeposition coating composition hardly generates pinholes or craters in the coated layer even if a zinc steel plate is used as an object to be coated, exhibits an excellent economical advantage since the amount of use of the electrodeposition coating composition itself can be small, and has a high throwing power that enables short-time electrodeposition with less influence given on the environment.
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