High-temp. galvanising process - with removal of excess iron@ from the molten zinc@ by means of a zinc removal and cooling stage

摘要

In a process for the high-temp. galvanising of articles made of iron or iron alloys, molten Zn is maintained at a temp. above 530 deg.C, pref. at 560 to 640 deg.C, and is not saturated with iron. Pref., the supersaturated iron is crystallised out from the molten Zn from time to time as an Fe/Zn phase by reducing the temp. of the molten Zn. This crystalline phase is then removed from the Zn. Part of the molten Zn is continuously or intermittently fed from the galvanising bath into a separate vessel, and a corresp. amt. is fed from the vessel back to the galvanising bath. The temp. in the vessel is maintained at a lower temp., partic. 530 deg.C. The molten Zn removed is cooled in a heat exchanger by means of the molten Zn fed back into the galvanising bath. USE/ADVANTAGE - Used to protect iron articles from corrosion by providing a relatively thin Zn layer which cannot be obtd. by other galvanising processes.