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PRECIOUS METALS PLATING
Electroplating includes passing an electric current through a
solution that’s called an electrolyte. This is done by dipping two
electrodes into the electrolyte and then connecting them into a
circuit with a battery or some other power supply.
SILvER Gold and Silver Plating - Deposition
Generally, silver is a more cost-effective plating solution; it The deposition of gold and silver is similar to other elec-
is cheaper than gold, and it also plates copper well. It has trodeposition processes. Considering the cost of precious
the highest thermal and electrical conductivity of any metal. metals, deposition is done under very exact conditions
Other attractive characteristics of silver are that it has the (A/sec.m 2) so that the layers can be deposited with precise
highest optical reflection, whitest color, and lowest contact thickness. Special care needs to be taken in order to mini-
resistance of all metals. mize the losses of noble metals during the post-plating
Issues that may arise with silver plating include galvanic rinsing process.
corrosion and humidity. Silver plating is not recommended
for applications that are subjected to humidity since it is After-Treatment
prone to flaking and cracking, which could eventually Normally, gold layers don’t need an after treatment. Some-
expose the base substrate. times the layer is gently polished with a soft tissue. Silver
With the exception of luxury goods, the industries that layers sometimes get coated with a thin layer of rhodium.
utilize silver plating the most are the electronics (semicon-
ductors and connectors, musical instruments, and bearings) wHAT IS ELECTROPLATInG?
and modern power generation (battery and solar). Electroplating includes passing an electric current through
a solution that’s called an electrolyte. This is done by dip-
PRECIOuS METALS COATInG PROCESS ping two electrodes into the electrolyte and then connecting
The electroplating of precious metals such as silver and them into a circuit with a battery or some other power
gold coatings can be done from a variety of aqueous supply. The electrolyte and electrodes are made from care-
electrolytes. Typically, solutions of cyanides are used. fully chosen compounds or elements. When the electricity
flows through the circuit that they complete, the electrolyte
Pre-Treatment separates. At this point, some of the metal atoms it contains
The pre-treatment depends on the condition of the com- are deposited in a thin layer on the surface of one of the
ponents that need to be treated and generally includes the two electrodes, thereby completing the electroplating
following process: process. All sorts of metals can be plated in this way, in-
• Mechanical pretreatment cluding gold, silver, platinum, etc.
• Degreasing Electroplating is similar to electrolysis (it includes using
• Rinsing electricity to split up a chemical solution). These are all
• Activation, sometimes by making the examples of electrochemistry, which is a chemical reaction
substrate electrically conductive caused by producing electricity that gives industrially or
• Rinsing scientifically useful end-products.
• Nickel or copper deposition
• Rinsing HOw ELECTROPLATInG wORkS
First, we need to choose the right electrolyte and electrodes
by deciding on the chemical reactions we want to create
36 CAnADIAn FInISHInG & COATInGS MAnuFACTuRInG nOvEMbER/DECEMbER 2020
