Current during pure metal deposition

Gases which may still be present in the flask during the refining of the Ti are bovuid by the metal (thus, a small amount of nitride is often formed). For this reason, the current to the first wire is shut off after a certain time and that to the second wire, dg, is turned on the Ti metal which then deposits on dg is completely pure. Because of the gradual build-up of titanium, the current must be raised up to 200 amp. when the ingot reaches a thickness of about 5 mm. This requires about 24 hours if the starting material is the crude Ti obtained from the hexafluoro-titanate, the build-up rate is lower. 

Stringers that tend to form during deposition of Al on the cathode may cause short circuits within a short time. Technical devices such as scrapers have been developed for stripping the aluminium from the cathode [296, 310] see also [421]. In order to minimize short circuits by particulate metal collecting on diaphragms, periodic current reversal is proposed [494]. The process was also suggested to serve In simultaneously refining commercially pure aluminium [291, 294, 301, 314, 350]. 

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