Electroplating porosity

Plate thickness is an important factor in electroplating, in terms of both performance and economics. Corrosion resistance, porosity, wear, appearance, and several other properties are proportional to plate thickness. Minimum plate thicknesses are, or should be, specified as should the location, or check-point, where the thickness is to be measured. In some appHcations, such as threaded fasteners, maximum thicknesses should be specified. Root diameters of finer machine threads can be adversely affected by as Htde as 10 p.m of plating. 

It will be seen that the design of articles to be electroplated can have a considerable effect on the corrosion resistance of the electrodeposited coating. The chief effects are the result of variations in deposit thickness, but also important are features which can influence the adhesion, porosity and physical properties of the deposit. Good design will also avoid features of the plated article capable of trapping liquids or solid contaminants which might cause more rapid corrosion. 

In this study, activated carbon fibers (ACFs) deposited by copper metal were prepared by electroplating technique to remove nitric oxide (NO). The surface properties of ACFs were determined by FT-IR and XPS analyses. N2/77K adsorption isotherm characteristics, including the specific surface area, micropore volume were investigated by BET and t-plot methods respectively. And, NO removal efficiency was confirmed by gas chromatographic technique. From the experimental results, the copper metal supported on ACFs appeared to be an increase of the NO removal and a decrease of the NO adsorption efficiency reduction rate, in spite of decreasing the BET S specific surface area, micropore volume, and micro-porosity of the ACFs. Consequently, the Cu content in ACFs played an important role in improving the NO removal, which was probably due to the catalytic reactions of C-NO-Cu. 

Nickel coatings are usually prepared by electroplating. The metal is plated either directly on steel or sometimes over an intermediate coating of copper. The copper underlayer is used to facilitate buffing of the surface on which nickel is plated, because copper is softer than steel, and also to reduce the required thickness of nickel (which costs more than copper) for obtaining a coating of minimum porosity. The automotive industry uses nickel as an underlayer for microcracked chromium to protect steel [9]. 

Some trials have shown differences between types of zinc coatings. Thus, both Biestek (1961a) and Hippensteel and Borgmann (1930) found that zinc electroplated from cyanide baths corroded 50% faster than zinc deposited from sulfate baths when measured as time to first rust. Uniformity, porosity, and possibly grain size may be responsible for these differences. Porosity (which is an indication that a greater amount of zinc surface per unit of mass is exposed) will lead to increased corrosion, as was shown by Hudson and Stanners (1953) for unsealed sprayed zinc. However, such differences are minor—usually under 10%—and do not occur on sealed zinc spray, which has much slower corrosion rates (AWS, 1974). 

The bond systems used with cBN are the same as those with diamond— resin, vitreous, metal, and single layer (electroplated or brazed)—but the relative prevalence is different. The most popnlar bond systems with cBN are vitreous and single layer, the reverse of the sitnation with diamond. In many cases the lifetime, finish, and grinding efficiency of vit-leons bond cBN wheels are superior to those of corresponding resin bond wheels. Factors contribntmg to the performance of vitreous bonds are hardness, thermal conductivity and stability, and higher porosity (which simplifies wheel surface conditioning) than resin bonds. 

Copper-rich waste discharged to lagoons behind an electroplating operation has percolated down to the water table, creating a plume of dissolved copper. Analysis of the porous medium and associated pore water indicate that the aquifer bulk density is 2.5 g/cm, porosity is 0.3, the copper concentration in the pore water is 10 mol/liter, and the copper concentration on aquifer solids is 10 mol/kg. If groundwater seepage velocity is 600 ft/yr, how fast will the plume advance ... 

R. J. Morrissey, Electrolytic Determination of Porosity in Gold Electroplates - II Controlled Potential Techniques, J. Electrochem. Soc. 119 (1972) 446. 

Macroporous open-cell nickel foam substrate was manufactured by the nickel electroplating of the polyurethane foam samples (cell density 60 ppi) followed by sintering in the dissociated ammonia atmosphere at 1100°C for 1 h. The foam samples were then deformed by a imiaxial compression to 1 mm thickness modifying the cell morphology and decreasing porosity from 95.5 % to 60-80 %. Deformed foams were subjected to the pack aluminizing and then annealed at 1000 C for 1 h under air to form a thin a-aliunina layer over the foam cell walls/ribs for a better adhesion of composite layers. 

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