Electroplating continued nickel

Soni PR, Rajan TV, Ramakrishnan P, Continuous nickel electroplating of carbon fibers and Weibull analysis of their tensUe strengths. Metals Mater Proc, 8(2), 187-191, 1996. 

Although most nickel sensitization results from nonoccupational exposures, nickel dermatitis was historically a problem in workplaces where there was a high risk of continuous contact with soluble nickel, eg, in electroplating (qv) shops. Improved personal and industrial hygiene has largely eliminated this problem. However, there are a few occupations involving wet nickel work, particularly where detergents faciUtate the penetration of skin by nickel, where hand eczema may occur (126). 

Specification for electroplated coatings of 65/35 tin/nickel alloy Method for the evaluation of results of accelerated corrosion tests on metallic coatings Methods of test for paints Cross-cut test Pull-off test for adhesion Resistance to artificial weathering (enclosed carbon arc) and Addendum No. 1 Resistance to continuous salt spray Notes for guidance on the conduct of natural weathering test... 

Typically, coatings most often in use as intermediate layers are silver, nickel, copper, and gold however, silver is used by far the most often. This is so because of the low dissociation temperature of silver oxide, making it relatively easy to obtain clean surfaces. Also, the typical thickness range of electroplates used, in practice, for diffusion welding is about 15 to 40/rm, but thicknesses as great as 130 )um must sometimes be used. A considerable variety of steel types as well as aluminum and a host of other difficult-to-join metals and even beryllium have been and continue to be diffusion bonded with the use of electroplated intermediate layers. 

Once all the copper is electroplated, concentrated ammonia is added to the remaining solution (iron if present is precipitated as its hydrated oxide and removed by filtration) and nickel is plated on another cathode at 4 A and 3—4 V. The test for completeness of deposition is carried out either by adding water and continuing the electrolysis or by testing with di-methylglyoxime. 

A work-site survey was carried out in all 38 Finnish electroplating plants (Kanerva et al. 1997). All 163 platers were interviewed and a random selection of workers was patch tested. Nickel allergy was found among 15% of the female workers and 4% of the male workers, which was the same frequency as recorded in Finnish dermatitis patients (Table 3). Seventy percent of those with nickel allergy reported past or present hand eczema. The study also indicated that sensitised workers often, but not always, were able to continue their work in the electroplating industry. 

Fig. 8.19 A continuous reel-to-reel electroplating line. The machine is a four-strand device which incorporates pretreatment sections prior to electroplating. A typical application is the selective electroplating of gold spots onto nickel-iron lead frames, which is an important stage in the manufacture of integrated-circuit packages. (Courtesy S. G. Owen (Northampton) Ltd.)...

Some materials contain an almost unlimited supply of material that can outgas. For example, brass, if heated in a vacuum, will continually outgas zinc, which will interfere with deposition on the brass surface. In this case, the brass must be sealed before coating. This is generally done with electroplated nickel or nickel-palladium (Sec. 2.6.4). Polymers that outgas significantly can be coated with a basecoat that seals the surface. 

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