Metal Finishing Guide Book


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kets filled with nickel of a selected size has become the preferred method of nickel plating. Titanium anode baskets are preferred because they offer the plater a number of advantages. Primary forms of nickel can be used that provide the least costly nickel ion source. Anode replenishment is simple and can be automated. The constant anode area achieved by keeping baskets filled improves current distribution and conserves nickel. Several forms of primary nickel are currently being used in baskets. These include electrolytic nickel squares or rectangles and button-shaped material that contains a small, controlled amount of sulfur. Nickel pellets produced by a gas-refining process and similar pellets containing a controlled amount of sulfur are being utilized. Prior to the introduction of titanium anode baskets, wrought and cast nickel anode materials were the norm. They are still used, but not to the extent they were before 1960. The wrought and cast anode materials comprise rolled bars containing approximately 0.15% oxygen; rolled nickel containing approximately 0.20% carbon and 0.25% silicon; and cast bars containing approximately 0.25% carbon and 0.25% silicon. Soluble auxiliary anodes are generally carbon- and silicon-bearing small-diameter rods. With the exception of the sulfur-bearing materials, nickel anodes require the presence of chloride ion in the plating bath to dissolve efficiently. Rolled or cast carbon-bearing materials are used up to a pH of 4.5, and oxygen-bearing, rolled depolarized anode bars can be used above a pH of 4.5 when chlorides are present in solution. REFERENCES 1. Brown, H. and B.B. Knapp, ���Nickel,��� in Lowenheim, F.A. (Ed.), Modern Electroplating, 3rd Ed., pp. 287-341; John Wiley, New York; 1974 2. American Society for Testing and Materials, ���Standard Practice for Use of Copper and Nickel Electroplating Solutions for Electroforming,��� in Annual Book of ASTM Standards, Section 2, Vol. 02.05, B 503-69; ASTM, Philadelphia; 1993 349

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