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By increasing the percentage of highly dissociative strong acid components included in the neutralizing acid of the electrodeposition coating, it was possible to improve electrical conductivity and coulomb efficiency and achieve excellent throwing power. The GA cratering caused by the increase in the strong acid ratio was resolved by setting the strong acid ratio to 90% while reducing MEQ. By increasing coulomb efficiency, the quantity of hydrogen gas produced during electrodeposition was minimized, and as a result, gas pinholes remaining in the coating were reduced, increasing the smoothness of the coating beyond than that of the current materials. As a result of this study, the usage of e-coating per vehicle body was reduced by approximately 11%.

Organic tin compounds were examined as replacements for the hardening catalyst function of lead in order to produce a lead-free cationic E-coat. The mechanism of the decline in adhesion, at the interface between the anti-chip primer and the primer surfacer, when an organic tin compound migrated to the anti-chip primer layer, was determined. Monobutyl tin compounds were found to have the lowest mobility within the film of organic tin compounds capable of functioning as hardening catalysts. A lead-free E-coat, employing a monobutyl tin compound, demonstrated no decline in adhesion, and the performance of the film was equivalent to that of conventional E-coat.

A new electrocoating has been developed as part of the ongoing efforts to move towards the use of lead-free cationic electrocoatings as auto body primers. The new e-coat dispels concerns such as increased cost and inferior rust protection due to the absence of lead, and will be able to be easily introduced to automotive production lines. Several technologies were necessary for this development: new corrosion inhibitors, essential for rust protection; improvement of the perfomance of the base resin of the paint film; and methods to control the viscosity of the deposited film in order to prevent deterioration of the workability and the appearance of the paint.