| 摘要 |
<PICT:1039285/C6-C7/1> A tube of e.g. steel is coated on its inner surface with tin, copper, cadmium, brass, bronze or as shown zinc by deflecting the tube by a quadrant 16 to form a loop whilst passing through a bath of molten zinc 15 and providing a sump of molten zinc in the loop. A layer 23 of flux based on zinc and ammenium chloride, floats on the entry end of the sump. The zinc may be introduced either in molten form through holes at points where the tube is to be subsequently sawn into lengths or as shown in the form of a wire 8a and the level of the sump maintained by varying the diameter of or the rate of feed of the wire. A measuring instrument based on the use of gamma rays may be used to detect the level of the sump. Instead of simultaneously coating the outside of the tube by immersion it may be coated by electro-deposition. The temperature of the zinc is maintained between its melting and vapourization temperatures and is preferably 700 DEG C. |
