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The essential requirements for the industrial preparation of potassium gold cyanide (PGC) are: (a) high rate of dissolution and (b) smooth and uniform dissolution. Employing galvanostatic and potentiostatic polarisation data and observations on the surface topography of anodes dissolved by both the techniques, it is shown that potentiostatic dissolution of gold in potassium cyanide at +0-345V satisfies the above requirements.

Ensuring the maximum reliability of the gold plating on lightweight alloys used in space applications is a difficult and challenging task. In this article, the authors describe the processes that they have found to meet requirements.Aluminium, magnesium, titanium and their alloys are increasingly used as the lightweight structural materials in aircraft and space applications, where lightness is always at a premium. To meet the end requirements (e.g., for improving corrosion and wear resistance, for increasing surface conductivity, for thermal control, etc.) surface coatings are applied to modify the surface properties. Unfortunately, plating on these lightweight structural materials is difficult. These metals and alloys belong to the group of difficult-to-plate materials. The basic problem stems from their high electrochemical potential in aqueous solution and their consequent high reactivity in air even at room temperature. As a result, they are always covered with a tenacious surface oxide film which prevents metal-to-metal bonding, thus leading to poor adhesion.For space applications, the reliability of the plating should be 100 %. This means that the adhesion should be excellent and high quality deposits should be produced. Defective plating is unacceptable as it seriously affects the launching and/or functioning of the spacecraft. Stripping the defective deposits without damaging the sensitive components also poses problems. Hence it is mandatory to control deposit characteristics with very high reliability by surface preparation procedures, by careful selection and control of bath composition and operating conditions, and by post-plating handling procedures.

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