| ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ KAWASAKI STEEL TECHNICAL REPORT No.12 ( July 1985 ) Special Issue on Hot-and Cold-rolled Steel Sheets ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ |
| Development of Zn-Ni Electroplated Steel Sheets "River Hi-Zinc" and "River Hi-zinc Super" Koji Yamato, Toru Honjo, Toshio Ichida, Hirotake Ishitobi, Masato Kawai |
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Synopsis : A thin Zn-Ni alloy electroplated steel sheet RIVER HI-ZINC was developed to reduce the perforation corrosion of automotive panels. The Zn-Ni alloy, consisting of a Α single phase, contains about 12% Ni. Coating adhesion and weldability of the alloy are excellent. Its corrosion resistance is four times greater than that of pure Zn-coated steel with the same coating weight. However, phosphatability and paintability of Zn-Ni alloy are somewhat poor. In their improvements, Fe-P ( 0.5wt.%) was electroplated on the Zn-Ni alloy, and double-layered Fe-P/Zn-Ni electroplated steel RIVER HI-ZINC SUPER has been developed for use on the exposed side of automotive panels. Uniformly distributed small amount of P in the Fe-P layer enhances the phosphating reaction and contributes to forming closely-packed phosphophyllite, which improves wet adhesion and reduces creepages (blisters) after the 3-coat painting in corrosion tests. Moreover, the Fe-P layer reduces crater-form paint defects during the cationic electrodeposition. |
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