Structure and polarization properties of Zn-Nb films formed on steel sheet by sputtering

摘要

Zn-Nb films were formed on a steel sheet by helicon plasma sputtering in an argon gas atmosphere at 1.0 Pa, at RF power of 50 W and DC power of 50 mA. The structure and polarization properties of these films were studied using EPMA, X-ray diffraction and polarization curve measurements. Zn plate-like crystals in Zn-Nb films decreased with increasing Nb content, resulting in a smooth surface over the entire film at Nb content of 30 mass percent and above. The preferred orientation plane of Zn plate-like crystals was (0002) at 0mass percent Nb, while the orientation indices of (1011) and (1010)Zn increased with rising Nb content. At 30-60 mass percent Nb, the X-ray diffraction spectra showed a halo pattern characteristic of an amorphous structure. The corrosion current of Zn-Nb films, which was determined by polarization curves in 3 percent NaCl solution, decreased with increasing Nb content to reach a minimum value at 30-60 mass percent Nb, corresponding to an amorphous structure.