GB607680A - Improvements in or relating to methods of anodically electropolishing nickel and nickel-containing alloys and electrolytes suitable for use in said method - Google Patents

Abstract

607,680. Electrolytic polishing of nickel and nickel alloys. BATTELLE MEMORIAL INSTITUTE. Aug. 15, 1944, No. 15550. Convention date, July 23, 1943. Drawings to Specification. [Class 41] Nickel or an alloy containing at least 90 per cent of nickel is polished by anodic treatment in a concentrated acid bath in which is incorporated additional material to increase the solubility of the nickel salts formed; by this means nickel dissolved in the process is deposited at the cathode and objectionable increase of viscosity and precipitation of nickel salts from the bath is prevented. The bath may consist of phosphoric acid or a mixture of phosphoric and sulphuric acids, the addition consisting of hydrochloric acid or a soluble chloride, e.g. chloride of sodium, potassium, calcium, magnesium, nickel, aluminium or chromium. The addition may alternatively consist of a chlorinated organic acid such as monochloracetic acid. The chloride content may be equivalent to 0.04-2.5 per cent of HC1 with a preferred range of 0.04-0.4 per cent. The current density may be 50-300 amps. per sq. ft. The proportions of the bath may lie between 77-38 per cent H3PO4, 2-28 per cent H2SO4 and 15-34 per cent H2O with a minimum total acid content of 66 per cent and chloride addition as above stated. An alternative range of proportions is 85-21 per cent H3PO4, 0-45 per cent H2SO4, 15-34 per cent H2O with minimum total acid content of 66 per cent. Permissible values within these ranges depend on the temperature and the chloride content; ternary diagrams indicating ranges of proportions for temperature ranges of 80-140‹ F. and 90-125 F. are included in the Specification.