Effects of added surfactants in the acidic hypophosphite plating baths on the properties of the resulting electroless nickel−phosphorus (Ni−P) deposits on the brass substrates were studied. The surface appearance and microstructures were examined under a reflective optical microscope and a scanning electron microscope equipped with an in situ energy-dispersive X-ray spectroscopy with which the phosphorus contents were measured. The deposition rate and the corrosion rate of the Ni−P deposits were estimated respectively from the weight gains and losses after a period of time. It is found that the addition of suitable amounts of surfactants can increase the deposition rate up to 25% and reduce the formation of the pores on the surface of Ni−P alloys, as well as enhance the corrosion resistance of the deposits. The corrosion rate of the Ni−P alloys in 10 wt % HCl was determined. The corresponding corrosion rate fits well as an empirical power function having an order of near 1/3 in the amount of dissolved Ni−...

Effects of Surfactants in an Electroless Nickel-Plating Bath on the Properties of Ni−P Alloy Deposits

Phosphate Conversion Coatings - A Metal Pretreatment Process

A novel Ag catalyzation process using swelling impregnation method for electroless Ni deposition on Kevlar ® fiber

The influence of a surfactant on the composition of nickel – yttria stabilised zirconia (YSZ) cermet coatings, applied by electroless nickel plating technique was examined. The amphiphilic characteristics of anionic surfactant sodium dodecyl sulphate (SDS), was relied upon for enhanced dispersion of YSZ particles co-deposited for use as anodes in solid oxide fuel cell technology and potential heat absorbing layers in thermal barrier coatings. Optical microscopy was employed to study the correlation between the plating thickness, level of ceramic loading and SDS concentration while the effect of the surfactant and fineness of YSZ particles on the as-deposited coating’s ceramic to metal ratio, was analysed using energy dispersive X-ray analysis (EDXA) characterisation technique.

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Effect of Sodium Dodecyl Sulphate on the Composition of Electroless Nickel—Yttria Stabilized Zirconia Coatings

Impurity partitioning in Nafion and ceramic separators used for purification of spent chromium plating solutions

Pit-free nickel electroplating

Chromium plating finds not only decorative but also functional applications. Generally chromium deposits are obtained from electrolytes with an approximate ratio of 100:1 of chromic acid to sulphuric acid. The Self Regulating High Speed (SRHS) chromium plating electrolytes, which are often employed for hard chromium plating though of higher efficiency have the disadvantages of cathodic etching and higher corrosivity. These are mainly due to the presence of a fluorine compound as a bath constituent. In this paper we report the results of experiments carried out with nonetching electrolytes but containing sulphate and potassium iodate. Different concentrations of chromic acid, sulphate and potassium iodate were used and current efficiency, rate of build-up, throwing power, deposit nature and microhardness were evaluated

Influence of potassium iodate on chromium deposition

Chromium electrodeposition is nowadays considered as one of the most imporomt electrodeposition processes. Chrome deposits are used both for decorative and for functional applications. A thin, hlue-tinged chrome deposit is normally applied on nickel undercoats in the decorative nickel-chromium finish. Such nickel-chromium decorative finishes are applied on a number of decorative articles like cycle components, automobile components, household articles, office furnitures, etc. In industry a thick chromium deposit is used as hard chromium and is used to coat on a numher of components which are resistant to wear and tear. The high hardness of chromium resists wear and tear and improves the service life of the components. Such an industrially important chromium is normally deposited from conventional chrome hath consisting of 250 g/l chromic acid and 2.5 g/l sulphuric acid and operated at 323 K and at a current density of 15.5 and 46.5 A/dm2• Chromium is deposited from hexavalent chromium using insoluble anodes. However, during the normal working of the bath, there is a gradual increase in Cr3+ concentration in the hath due to the incomplete oxidation of Cr3 + and Cr6+ at the anode. Buildup of Iron(III) in chrome bath occurs in a number of ways. They are a) carry over from previous operations due to poor washing of the components d) dissolution of substrate when jobs are allowed to be in chrome bath without current, c) due to anudic etching from the plating bath itself and d) etching of fallen articles remaining in the hath. Thus the entry of Cr3+ and Fe3+ are inevitahle in the chromium bath. In order to study tbe effect of iron and trivalent chromium in the production of chrome deposit the study was undertaken and the results on the nature of the deposit, current efficiency, rate of build up, hardness and porosity are presented in this paper.

C. J. Kennady

Papers

Pit-free nickel electroplating

Influence of potassium iodate on chromium deposition

Effect of trivalent iron and trivalent chromium ions on chromium plating