Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 225 of 707

Watts Nickel NiSO4 BO3 Ni(SO3NH2 NiCl26H2 H3 6H2 O O )2 4H2 O 225 to 300 37 to 53 30 to 45 Temperature, o Agitation C Current density, A/dm2 Anodes pH Tensile strength, MPa Elongation, % Air or mechanical 3 to 11 Nickel 44 to 66 3.0 to 4.2 345 to 485 15 to 25 Vickers hardness, 100 g load 130 to 200 Internal stress MPa 125 to 185 (tensile) Conventional Sulfamate Electro Composition, g/L 315 to 450 30 to 45 0 to 22 Operating Conditions 32 to 60 Air or mechanical 0.5 to 32 Nickel 3.5 to 4.5 Mechanical Properties 416 to 620 10 to 25 170 to 230 0 to 55 (tensile) Table III. Nickel Electroplating Solutions and Typical Properties of the Deposits of this second of class brighteners are formaldehyde, coumarin, ethylene cyanohy- drin, and butynediol. The combination of organic addition agents makes it possible to obtain smooth, brilliant, lustrous deposits over wide ranges of current density. The deposits have a banded structure consisting of closely spaced laminations believed to be related to the co-deposition of sulfur. Certain cations, for example. zinc, sele- nium, and cadmium, enhance the luster of electrodeposited nickel, and have been used in combination with the organic additives. Supply houses provide instructions for proprietary bright nickel processes that specify rates of replen- ishment and methods of analyses for specific addition agents. Semibright Nickel Semibright nickel solutions contain nickel sulfate, nickel chloride, boric acid, and a leveling agent. The original process used coumarin as the principal additive. Coumarin-free processes are now available. The process yields deposits that are semilustrous. The deposits are smooth and have a columnar structure unlike the banded structure characteristic of fully bright deposits. The solution was developed to facilitate polishing and buffing; semibright nick- el deposits are easily polished to a mirror finish. Efforts to eliminate polishing led to the combination of semibright and bright nickel deposits. Experience has shown that a multilayer nickel coating has greater resistance to corrosion than a single-layer coating of equivalent thickness. Single Layer and Multilayer Nickel Coatings Single and multilayer nickel coatings are used to produce decorative coatings that resist corrosion. Single-layer bright nickel deposits are specified for mildly corrosive service. Double-layer coatings are specified for use in severe and very severe service. In double-layer coatings, the first nickel layer is deposited from a semibright bath. The second layer is then deposited from a bright bath. Triple-layer coatings may also be specified for severe and very severe service. In this case, a special 224 Concentrated Sufamate 500 to 650 5 to 15 30 to 45 normally 60 or 70 Air or mechanical Up to 90 Nickel 3.5 to 4.5 400to 600 10 to 25 150 to 250 see text

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