| 摘要 |
In electroplating a cathode of hydrogen overvoltage greater than that of etched high carbon (at least 0.6%) iron alloys, selected areas are stopped off by protecting them with a piece of etched high carbon alloy. The high carbon alloy may be cast iron or steel containing 0.6 to 0.98% carbon and the etching may be effected merely by immersion in the plating bath or by connecting it therein for a period as anode. The cathode is stopped off by placing the etched high carbon alloy immediately adjacent and preferably in electrical contact with the areas not to be plated. The invention may be applied to plating iron or low carbon steels including nickel steels and stainless steels in bright polished form with chromium from chromic acid baths containing sulphuric acid and siliconfluoride ion.
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