Thursday, March 20, 2008

Heavy Nickel Plating

Electrodeposited nickel is employed nickel is employed for resistance to process industry corrosion, for combined corrosion and wear resistance, and for salvaging worn or mismachined parts. It is also used for direct electroforming of articles which because of their intricate shapes or requirements for surface finish would be difficult or costly to produce by conventional metal working procedures. The thickness of nickel involve in such applications range from about 75 ┬Ám to the extreme realize in an electroformed supersonic wind tunnel section weighing 3635 kg and having a wall thickness ranging from 3.8 to about 10 cm.

High speed method of depositing nickel and other metals which may help in heavy nickel plating. This method involves the use of controlled abrasion during electroplating.

Bath Types:
Choice of bath composition is dictated primarily by the mechanical properties desired in the deposits. Engineers have turned to electrodeposition to solve fabrication or salvage problems because the mechanical properties of electrodesited metals can often be varied over wider limits than those of the same produced by conventional means. A summary of methodes, special precautions for, and applications of heavy nickel plating is available.

The various types of nickel baths used for the production of nondecorative deposits are listed in the table. Typical properties of deposits from these baths are also given. The Watts and sulfamate baths are by far the most widely used.

Watts Bath.
A typical composition for engineering for engineering applications is listed in the table. The deposits are ductile and relatively soft. Variations in the plating condition cause variations in the mechanical properties of the deposit in the manner previously described. Applications for such deposits are the production of coatings or electroforms that are to be subsequently drawn are formed, the plating of chemical vessels, pipe, and so on, for protection against corrosion.
Annealing for 15 min at 760 oC increases the elongation to 55%, which is sufficient for severe forming or drawing operations. Care must be taken not to over anneal, since this causes excessive grain growth and marked loss in ductility. Certain impurities in very small amount cause embitterment when heated; as little as 0.02% lead may have a noticeable effect. In addition, annealing should not be attempted with deposits containing sulfur, which is introduced if class I addition agents are used in the bath as stress reduced.

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