Magni 565 코팅 볼트의 제 특성에 관한 연구

Abstract

Layer thickness and corrosion resistance of M10 bolt coated with Magni 565 were investigated to find out the optimum coating conditions. Characteristics of the coated bolt were also studied. The main results obtained are as follows; 1. Optimal coating conditions for base and top coats for bolt were as follows; ① Zahn cup viscosity for base and top coats were 60 and 55 sec, respectively. ② RPM and time for base and top coats in dip/spin process were 260, 15 sec and 290, 15 sec, respectively. ③ Curing temperature and time for base and top coats were 250℃, 25 min. and 20 5℃, 25 min., respectively. The samples coated with optimal conditions showed around 10㎛ layer thickness and a great corrosion resistance in salt spray test with 1500 hours or longer of initial appearance time of rust. 2. The bolts with the optimum conditions showed a proper torque in torque/tension test. Torque coefficient k increased a little with the number of bolting and clamping force of M10 bolt showed significantly lower than that of specified value 28.3kN. It was thought that the repeated bolting made the coating film peel off and powdery. 3. Heat resistance temperature without cracks in coating film was below than 300℃. 4. Adhesion of the coating layer was good enough to have A~C grade adhesion and influenced little by surface roughness. 5. While aging of film in the ultra violet irradiation test was not observed in one week, a great decrease of polarization resistance in EIS was observed after 2 weeks. 6. Observed coating film defects were uncoated areas, excessive coating layer, cracks and unfastened areas and those defects were found mainly in the crest and root of the bolt threads. 7. The base coating film was composed of lamellar zinc flakes, which provides sacrificial cathodic protection. Meanwhile, the top coating film was composed of organic aluminium pigments layer, which provides barrier protection to the corrosion circumstances.