BASICS OF ELECTROPLATING – HOW IS ELECTROPLATING THE OPPOSITE OF CORROSION:

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Introduction:
Electroplating is a process whereby one metal is plated onto
another via an electrodeposition method. Customers seek out
electroplating for their parts for many reasons such as
aesthetics, corrosion protection, increased hardness, wear
resistance, increased conductivity, and decreased friction. It
allows manufacturers to use base metals that are less
expensive and apply a high quality coating to them to achieve
the certain desired properties on the finished part.


 There's no such thing as alchemy—magically changing
common chemical elements into rare and valuable
ones—but electroplating is possibly the next best thing.
The idea is to use electricity to coat a relatively mundane
metal, such as copper, with a thin layer of another, more
precious metal, such as gold or silver. Electroplating has
lots of other uses, besides making cheap metals look
expensive. One can use it to make things rust-resistant,
for example, to produce a variety of useful alloys like brass
and bronze, and even to make plastic look like metal. How
does this amazing process work? Let's take a closer look.

What is electroplating?
Electroplating involves passing an electric current through
a solution called an electrolyte. This is done by dipping two terminals called electrodes into the electrolyte and
connecting them into a circuit with a battery or other power
supply. The electrodes and electrolyte are made from
carefully chosen elements or compounds. When the
electricity flows through the circuit they make, the
electrolyte splits up and some of the metal atoms it
contains are deposited in a thin layer on top of one of the
electrodes—it becomes electroplated. All kinds of metals
can be plated in this way,
including gold, silver, tin, zinc, copper,
cadmium, chromium, nickel, platinum, and lead.
Electroplating is very similar to electrolysis, which is the
reverse of the process by which batteries produce electric
currents. All these things are examples
of electrochemistry: chemical reactions caused by or
producing electricity that give scientifically or industrially
useful end-products.

How does electroplating work?
First, you have to choose the right electrodes and
electrolyte by figuring out the chemical reaction or
reactions you want to happen when the electric current is
switched on. The metal atoms that plate your object come
from out of the electrolyte, so if you want to copper plate
something you need an electrolyte made from a solution of a copper salt, while for gold plating you need a gold-based
electrolyte—and so on.
Next, you have to ensure the electrode you want to plate
is completely clean. Otherwise, when metal atoms from
the electrolyte are deposited onto it, they won't form a
good bond and they may simply rub off again. Generally,
cleaning is done by dipping the electrode into a strong
acid or alkaline solution or by (briefly) connecting the
electroplating circuit in reverse. If the electrode is really
clean, atoms from the plating metal bond to it effectively
by joining very strongly onto the outside edges of its
crystalline structure. Now we're ready for the main part of
electroplating. We need two electrodes made from
different conducting materials, an electrolyte, and an
electricity supply. Generally, one of the electrodes is made
from the metal we're trying to plate and the electrolyte is a
solution of a salt of the same metal. So, for example, if
we're copper plating some brass, we need a copper
electrode, a brass electrode, and a solution of a
copper-based compound such as copper sulfate solution.
Metals such as gold and silver don't easily dissolve so
have to be made into solutions using strong and
dangerously unpleasant cyanide-based chemicals. The
electrode that will be plated is generally made from a
cheaper metal or a nonmetal coated with a conducting
material such as graphite. Either way, it has to conduct
electricity or no electric current will flow and no plating will
occur.

       

We dip the two electrodes into the solution and connect

them up into a circuit so the copper becomes the positive

electrode (or anode) and the brass becomes the negative

electrode (or cathode). When we switch on the power, the

copper sulfate solution splits into ions (atoms with too few

or too many electrons). Copper ions (which are positively

charged) are attracted to the negatively charged brass

electrode and slowly deposit on it—producing a thin later

of copper plate. Meanwhile, sulfate ions (which are

negatively charged) arrive at the positively charged copper

anode, releasing electrons that move through the battery

toward the negative, brass electrode.

It takes time for electroplated atoms to build up on the

surface of the negative electrode. How long exactly

depends on the strength of the electric current you use

and the concentration of the electrolyte. Increasing either

of these increases the speed at which ions and electrons

move through the circuit and the speed of the plating

process. As long as ions and electrons keep moving,

current keeps flowing and the plating process continues. 

Why to use Electroplating?

Electroplating is generally done for two quite different

reasons. Metals such as gold and silver are plated for

decoration: it's cheaper to have gold- or silver-plated

jewelry than solid items made from these heavy,

expensive, precious substances. Metals such as tin and

zinc (which aren't especially attractive to look at) are

plated to give them a protective outer later. For example,food containers are often tin plated to make them resistant

to corrosion, while many everyday items made from iron

are plated with zinc (in a process called galvanization) for

the same reason. Some forms of electroplating are both

protective and decorative. Car fenders and "trim," for

example, were once widely made from tough steel plated

with chromium to make them both attractively shiny and

rust-resistant (inexpensive and naturally

rustproof plastics are now more likely to be used on cars

instead). Alloys such as brass and bronze can be plated

too, by arranging for the electrolyte to contain salts of all

the metals that need to be present in the alloy.

Electroplating is also used for making duplicates

of printing plates in a process called electrotyping and

for electroforming.

Hope you liked and gained some knowledge about electroplating. Let's have a look on polymers in the next blog..

Stay Tuned!!!!