| 摘要 |
PROBLEM TO BE SOLVED: To produce a chromate treated metallic sheet excellent in chromium eluting properties by coating the surface of metal with an inorganic polymer formed of rare earth element ions and polyvalent oxo anions. SOLUTION: The surface of metal or the surface of plating subjected to chromate treatment is coated with an inorganic polymer formed of rare earth element ions (lanthanum and cerium) and polyvalent oxo anions (such as phosphoric acid). At this time, the molar ratio between the lantnanum ions and the phosphoric acid ions is regulated to about 2 to (1/100), preferably, to about (1/2) to (1/50), and more preferably, to about (1/5) to (1/19). The molar ratio between the cerium ions and the phosphoric acid ions is regulated to about 2 to (1/100), preferably, to about 1 to (1/50), more preferably, to about (1/5) to (1/15), and the coating thickness of the iniorganic coating layer is regulated to about 0.01 to 5μm. Furthermore, as the feeding source of lanthanum, lanthanum oxide or the like is preferably used, and as the feeding source of cerium, cerium phosphate or the like is preferably used. In this way, the chromate treated metallic sheet excellent in corrosion resistance can be obtd.
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