Malathy Pushpavanam

Methanesulphonic acid in electroplating related metal finishing industries

SUMMARY During the past ten years, methanesulphonic acid has largely replaced fluoroboric acid as the electrolyte of choice for the electrodeposition of tin and tin-lead solder on electronic devices. Certain other electrochemical processes involving lead, most notably the electrorefining of lead by the Betts process, are currently carried out in fluorosilicic acid based electrolytes but those based on methanesulphonic acid (MSA) are being actively investigated as environmentally superior alternatives to the currently used systems. Also, a number of commercial strip steel tinplating operations have recently converted to methanesulphonic acid based tin-plating electrolytes. There are also developing markets for methanesulphonic acid in silver, nickel, copper, cadmium and zinc electroplating. This paper reviews the chemical and physical properties of methanesulphonic acid and its current applications in the field of metal finishing and also its superiority over other electrolytes especially with respect to environmental pollution.

Role of Peptone in the Electrodeposition of Tin and Tin-Zinc Alloys from Neutral Gluconate Bath

SUMMARYPeptone addition in small amounts increased the current efficiencies of tin and tin-zinc alloy depositions on steel from gluconate bath. Increase of peptone concentration decreased the tin content and increased the zinc content in the Sn-Zn alloy deposit. Cyclic voltammetric studies revealed that peptone stabilized the monovalent tin. The discharge of zinc gluconate complex was favoured by peptone which caused higher zinc content in the alloy deposit.

Internal stress and hydrogen permeability of zinc-nickel alloy electrodeposits

SUMMARYA citrate based electrolyte has been studied as a substitute for the conventional bath containing ammonium chloride. The internal stress of the electrodeposits and their hydrogen permeability are studied in detail and compared with those of conventionally used cadmium and zinc baths.

Effect of Addition Agents on the Electrodeposition of INVAR Alloys

SUMMARY Iron-nickel alloy of ‘INVAR’ composition has been prepared from a sulphate-chloride bath. The effect of operating variables on the composition and current efficiency of alloy deposition was evaluated. The effect was studied of seven different additives belonging to the aromatic sulphonic acid group and thiourea derivatives on the characteristics of alloy deposition. Their effect on deposit nature, composition, cathode efficiency and microstructure, hardness etc., is reported.

A Modified process for iridium electrodeposition

SUMMARY As a noble metal, Iridium finds many applications in the industry. Electrodeposited iridium, as a thin coating, provides a cheaper method of using the metal wherever possible. Iridium and platinum-iridium alloy are used in industrial water electrolysis as anodes because of their low oxygen overpotential. Of all the baths available for electrodepositing iridium, the bromide electrolyte appears to be the best. Different methods of preparing the bromide electrolyte are compared: the one prepared using iridium chloride gives improved performance with respect to stability, current efficiency, higher deposit thickness, and appearance of the deposits, besides its cost effectiveness.

Electrodeposited Tin-Cobalt Alloy from a Neutral Gluconate Bath

SUMMARY Tin-cobalt alloy deposits are considered as an eco-friendly substitute to replace conventional chromium plating. A new gluconate bath has been used to produce this alloy and evaluate its properties. Alloys containing 30–40 per cent cobalt exhibit desirable properties, such as a pleasing appearance, pore-free nature, solderability and corrosion resistance which have been attributed to the alloy being in the CoSn phase.

A bromide electrolyte for the electrodeposition of platinum and platinum–iridium alloy

Abstract A new electrolyte is reported for the deposition of platinum and platinum–iridium alloy. The effect of operating variables and bath composition on the cathode current efficiency and alloy composition were investigated. The bath gives 75% efficiency for platinum deposition and around 50% efficiency for the alloy deposition with 70% iridium. Alloys with varying composition could easily be produced and the deposits obtained on titanium were smooth and adherent.

High throw nickel plating

SUMMARY Throwing power is an important factor in practical electroplating. Difficulties are often encountered while plating on curved or intricately shaped components. The throwing power of acid electrolytes, for example. Watts nickel, can be marginally improved by the change in cell design, electrode geometry, interelectrode distance etc., besides the addition of certain inorganic salts. The presence of hypophosphite ion improves the throwing power of a Watts nickel solution.

Shear strength of nickel electroplated on some difficult-to-plate metals

SUMMARY The adhesive strength of electroplated nickel on some of the difficult-to-plate metals such as titanium, stainless steel, and aluminium was measured using shear testing. Heavy nickel electrodeposits were produced on the above metals using different pre- and post-plating treatments. The work is a prelude to the electrochemical joining of these metals as required for space applications.

Electrochemically Prepared Tin-Lead Fluoborates for the Deposition of Sn-Pb (60:40) Alloy

SUMMARY The electrochemical preparation of lead and tin fluoborates offers the high quality lead-tin alloy electrodeposits required for a variety of industrial applications. The impurities present in commercially available fluoborates impair many of the desirable qualities of the alloy deposits, affecting their structure and orientation. This paper describes the merits of the alloy plating electrolyte prepared by an electrochemical route.