연속․순환식 공정으로 제조된 Zinc flake 도료의 방식성능 평가에 관한 연구

Abstract

In general, thinner coating for ship shop primer or main primer is favored. However, too thin coating causes poor anti-corrosion performance, and on the other hand good anti-corrosion performance of thick coating is often cancelled out with more cost and more post-treatments. The optimization technology is thus required to attain maximum anti-corrosion performance with minimum usage of zinc pigment. In this study, the anti-corrosion performance of organic zinc rich primer (ZRP) with zinc flakes (lamellar shape) incorporated is investigated in that zinc flakes expect to produce thinner coating but better anti-corrosion performance in zinc pigment. Zinc flakes have been used since 1970's, manufactured by ball milling. However, they have a couple of weaknesses. The manufacturing method has inferior yield and capacity, and the separation and dispersion of zinc flakes are not easy. Therefore, it is generally said that zinc flakes are ten times expensive than zinc dust. This study is thus focused on the development of mass-productive continuous- circulation complex bead milling (CBM) for the fabrication of zinc flakes, which gives 30 times more output per hour and over 90% yield. The organic zinc primer composed of the manufactured zinc flakes is then tested for the comparison with the zinc pigment made from zinc dust. The coated samples are evaluated by adhesion test, film thickness measurement, impact test, salt dipping test, salt spray test, etc. as usually done. In addition, the long-term anti-corrosion performance is checked by electrochemical impedance spectroscopy(EIS) under an accelerating condition. Finally, the mixing of zinc flakes and dust is proposed for the commercialization. The experimental results show that zinc flakes manufactured through continuous-circulation CBM processes have the same anti-corrosion performance even with less than 50% usage compared to zinc dust. Moreover, the performance is increased by over 20% when an optimum amount of zinc dust is mixed with zinc flakes, probably due to the better barrier effect. In other words, their different particular shapes make them to be more efficiently stacked. The potential of zinc flakes of this study, manufactured by economical continuous- circulation CBM processes, is expanded to more various applications.