|New, Eco-Friendly Process for Non-Cyanide Silver Electroplating on Electrical and Electronic Components.|
The Shubhra ™ non-cyanide silver electroplating process contains absolutely no cyanide in any form. As with the current cyanide-based silver electroplating processes, the SHUBHRA™ process operates at room temperature and the bath is alkaline, but with a milder pH value of 10.0.
The range of addition of various ingredients per litre of the electroplating bath is given below:
Standard equipments are used for the process and standard process sequence is followed. However, no strike silver plating is necessary in the SHUBHRA® process for copper and copper alloys. All organic components of the bath are fully bio-degradable. The process can be carried out both in barrel and in vat mode. The deposits are fine-grained and uniform and have hardness up to 140 HV 0.1. The bath has excellent metal distribution and no immersion deposition occurs. The wear resistivity of the coating obtained by the Shubra ® process is superior.
Following typical research and development studies over several years, laboratory trials, pilot-plant trials and commercial trials, this cyanide-free process is now available for electroplating of silver in barrel or vat mode.
Silver electroplating is an age-old and well-established process. The classical silver electroplating bath chemistry depends on silver potassium cyanide in water and large amount of free cyanide, usually in the form of potassium cyanide.
Many cyanide silver plating baths contain strong chelating agents such as EDTA, making effluent treatment difficult. Also, some of the brightening agents are based on toxic metals such as selenium, bismuth, antimony and arsenic. However, the greatest disadvantage of such baths is the cyanide. The operators have to work with extreme care, taking all safety precautions. Further, the effluent contains free cyanide and must be properly treated to destroy the free cyanide. The occupational hazards of having to handle such toxic and poisonous chemicals are obvious. The LD50 for potassium cyanide and hydrogen cyanide are 5 mg/Kg body weight and 1-3 mg/Kg body weight, respectively. Moreover, hydrogen cyanide is rapidly absorbed when inhaled and is fatal.
For these reasons, the need for a stable, commercially viable and cyanide-free alternative for silver plating has been developed in-house, with particular reference to electrical and electronic components.
The new process can be used for silver plating of all electrical and electronic components, including toggle and slide switches, contact tips, switchgear components, bus bars, new or worn-out electrical contacts, fasteners, diplexers, antennae parts, bearing surfaces and others.
Fig.: Typical components silver-plated by the Shubra™ process
Moreover, the process can conveniently be used in the form of a kit on-site to do brush-plating of bus-bars, without having to dismantle the whole assembly and transporting it. The entire process is non-hazardous and does not require special equipment or procedures for storage, transportation and disposal.
A newly developed cyanide-free silver electrolyte has been tested under standard production conditions. It allows technical silver-plating without the use of cyanide.
No pre-silver plating is necessary for coating non-ferrous metal materials. The properties of the coatings deposited from this solution are at par with known characteristics pertaining to cyanide electrolytes.
Additional advantages to be gained involve occupational and industrial safety and improved waste-water treatment.
Mr. Puneet Rane
RRR House, Plot 80, Sector- 23, CIDCO Industrial Area
Navi Mumbai - 400705, Maharashtra, India
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