Thiosulphate baths for silver plating

Electroplating silver from thiosulphates solutions has received increasing attention recently because of the emphasis on pollution-free prooesses. This paper reports the results of studies for identifying suitable compositions for silver plating. Different aspects encompassing stability, mnductivity, cathode current efficiencv. deposition rate and throwing power of solutions as well as deposit properties like appearance. microhakness and adhesion were examined. The preplating sequence fro improving deposit adhesion was also investigated. The studies enabled identification of two methods of wetreatment and production of sound deposits with good adhesion to copper and.nickel plated copper. specimens

Electrodeposition of zinc from acetate based electrolytes

Zinc electrodeposits are widely used to protect iron and steel from corrosion which are relatively inexpensive. Zinc coatings are nomlally ohtained from chloride and nOD-cyanide alkaline baths. The environmental corrosion along with the electrolytes sensitivity towards metallic impurities limit the use of chloride electrolyte. The use of additive, less cathode efficiency and the emuent treatment do not permit the use of non-cyanide zinc plating baths to a greater extent. Hence, the need for the search for a better zinc plating electrolyte is necessary. In this paper the authors present the details of zinc plating from an acetate based electrolyte and the result of Hull Cell studies are presented in thi~ paper

Electropolishing of electroplated silver

Electropolishing of silver from cyanide based electrolytes is investigated and reported in this paper. Effect of varyin~ bath ingredients, addition of certain additives, influence of applied voltage resulting current-time behaviour,dissolution rate of silver, surface appearance aDd brightness after treatment etc. are studied in detail to arrive at the optimum composition and operating parameters

Evaluation of. Performance of electroplated cu-ni-cr and double layer ni-cr coatings on mild steel

Various types of decorative copperr-nickel-chromium electrodeposits were produced on mild steel substrates and their corrosion resistance evaluated by means of CASS and Corrodkote accelerated tests and also by exposure tests at Mandapam Camp, a locality with a tropical marine atmosphere. The behavio~. f the electrodeposits was examined by anodic polarisation in CASS and Corrodkote media. The results of all the above investigations are presented in this paper

A simple method for the preparation of ruthenium plating solution

Ruthenium is the least expensive of the platinum group metals, and is an attractive altemative to both rhodium and gold in contact finish applications, as in electronics. Ruthenium in sealed-reed contacts to resist contact sticking, is a noteworthy application. However much ruthenium can be applied for a particular purpose, the availability of satisfactory electroplating processes demands an extensive investigation for the establishment of the same. Hence there is a need to get a standard basic electrolyte which can help getting a good uniform and smooth deposit of ruthenium ontinuously, witbout any deterioration of the electrolyte. Till today there has heen no citation in literatUl-e regarding the same. l11e present paper focuses on the method of preparation of ruthenium platin~ concentrate, it.. st.'lbility with time, and some of its performance characteristics

Effect of various sulphates on chromium plating

For chromium plating, along with chromic acid a small quantity of sulphate ion is very much essential. In the absence of sulphate ion the chrome bath will not produce any bright deposit but will produce only brown film. The sulphate ion is nonually introduced as sulphuric acid at a ratio of 100:1 to chromic acid. In this paper, in order to study the effect of other sulphate ions, it is aimed to study the effect of cations associated with sulphates. The SUlphate to the chrome bath was introduced in the form of sulphuric acid, sodium sulphate, ammonium sulphate, potassium sulphate and chromium sulphate. Hull Cell experiments were carried out to study the nature of the deposit. Plating expe:;ments were also carried out to study the current efficiency, rate of buildup, porosity, hardness, and nature of deposit and the results are presented

Effect of trivalent iron and trivalent chromium ions on chromium plating

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

A simple method for the preparation of ruthenium plating solution

Ruthenium is the least expensive of the platinum group metals, and is an attractive altemative to both rhodium and gold in contact finish applications, as in electronics. Ruthenium in sealed-reed contacts to resist contact sticking, is a noteworthy application. However much ruthenium can be applied for a particular purpose, the availability of satisfactory electroplating processes demands an extensive investigation for the establishment of the same. Hence there is a need to get a standard basic electrolyte which can help getting a good uniform and smooth deposit of ruthenium ontinuously, witbout any deterioration of the electrolyte. Till today there has heen no citation in literatUl-e regarding the same. l11e present paper focuses on the method of preparation of ruthenium platin~ concentrate, it.. st.'lbility with time, and some of its performance characteristics

Electrodeposition of silver from low concentrated cyanide electrolytes

Silver is used as a deposit for decorative and aesthetic appeal on jewellery, hollowers, flatware etc. It is also used in engineering industries for various reasons like high heat and electrical conductivity and good antigalling property on bearings, electronic components like socket contacts, ~lip rings, switch gear and wave guides for radars etc. Usually, silver is electroplated from cyanide based electrolytes and these solutions contain higher concentrations of both silver and cyanide causing heavy pollution due to emuents. Also. silver being costly, it was considered worthwhile to investigate the feasibility of evolving a bath formula with low concentration of silver as well as cyanide with equivalent characteristic features to the concentrated baths. Experiments were carried out with different concentrations of silver and cyanide and the results are compared with that of conventional cyanide based baths

Electroplating of nickel-copper alloys

Nickel-copper alloy with 30% nickel has Monel like properties with excellent resistance to corrosion and erosion. This alloy deposited over steel substrate has been recommended as a cost-effective replacement for cast Monel for applications in different environment. This paper deals with investigations on the development of a stable bath for electroplating this alloy. A suitable bath is reported on the basis of Hull cell studies, plating experiments, determination of alloy plating efficiency and composition of the plated alloy. Effects of operating parameters on deposition characteristics and deposit properties are also reporte