| 摘要 |
<p>Hot-dipped steel plate produced by dipping steel in a plating bath of zinc-base or zinc-aluminum-base alloy, and a process for its production. Hot-dipped steel plate has on its surface a film of cobalt oxide, iron oxide or both of them, and this oxide film serves to prevent the plate from discoloring to grayish black when said plate is one treated to minimize spangles, or it has a plating layer which contains a corrosion resistance-improving element such as magnesium or aluminum, or otherwise it is one chromated after machining. The oxide film is formed on the surface of the hot-dipped steel plate by spraying an aqueous solution containing a cobalt or iron salt or both of them against the surface of the plating layer having a temperature of 170oC or above to thereby thermally decompose the salt. Preferred salts include nitrates and chlorides of cobalt and iron.</p> |
