Page 37 - CFCM Nov-Dec-2020 Final_Neat

when the electric current is applied. The metal atoms that
plate an object come from the electrolyte, so if we want to
gold plate something, we need a gold-based electrolyte,
and so on.
Next, we need to make sure the electrode we want to
plate is entirely clean. If it’s not clean, the metal atoms
from the electrolyte can’t form a good bond with the sur-
face, allowing them to be easily removed with friction.
Usually, the cleaning is done by dipping the electrode into
a strong alkaline or acid solution or by connecting the
electroplating circuit briefly in reverse. When the electrode
is completely clean, atoms from the plating metal can bond
to it effectively by adhering to the crystalline structure’s
outside edges.
Now we’re ready for the most important part of electro-
plating. We need an electrolyte, two electrodes that are
made from different conducting materials, and an electricity
supply. One of the electrodes is usually made from the
metal we want to plate, and the electrolyte is usually a
solution of a salt of the same kind of metal. So, for example,
if we’re silver plating a piece of brass, we need a
silver electrode, a brass electrode, and a solution of a
silver-based compound. Precious metals like silver and
gold don’t easily dissolve, which means they require strong
and dangerous cyanide-based chemicals to be made into
electrolytic solutions. The electrode that will be plated is
typically made from a more affordable metal or a nonmetal
material coated with a conducting material like graphite.
In either case, it needs to conduct electricity in order for
the plating to occur.
We dip these two electrodes into the solution and
connect them into a circuit, so the silver becomes the
positive electrode, and the brass becomes the negative
electrode. When we turn the power on, the silver sulfate
solution splits into ions (atoms with too many or too
few electrons). Silver ions (that are positively charged)
are attracted to the negatively charged electrode and
slowly deposit on it, creating a thin layer of silver plate.
Meanwhile, sulfate ions (that are negatively charged)
will get to the positively charged copper anode and
release electrons that move through the battery to the
negative electrode.
It takes some time for electroplated atoms to build up
on the negative electrode’s surface. How long this will
take depends on the strength of the electric current used
and the concentration of the electrolyte. Increasing either
of these factors can increase the speed at which electrons
and ions move through the circuit, which will increase
the speed of the whole plating process. As long as
electrons and ions continue to flow, the plating process
will continue. n

Paul Fredericks is Founder and CEO, Aerospace Metals LLC. Jeff
Logan is President, Saporito Finishing.

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