Heap Electro Galvanized Plating

THE PURPOSES OF ELECTOPLATING
Some of the purposes for which articles are electroplated are:
(1) Appearance
(2) Protection
(3) Special surface properties
(4) Engineering or mechanical properties.
The distinctions between these aims are not, of course, clear-cut and there are many
overlapping categories. A deposit applied purely for appearance must be, at least to some
extent, protective as well. But the classification is convenient.
Some finishes are purely decorative. Many objects meant to be used indoors, in a dry
environment and where danger of corrosion is slight, are nevertheless finished with lacquers,
paints and electroplated coatings for purely aesthetic reasons. The very thin layer of gold
applied to some articles of inexpensive jewellery has little or no protective value; it is there
principally to attract a potential buyer.
There are many applications of electroplating, some of them of increasing importance at
present, in which neither corrosion prevention or decorative appeal is the reason for using a finish. Copper is an excellent conductor of electricity and is therefore basic to such items as
printed circuits and communications equipment. It does, however, quickly form tarnish films
that interfere with joining operations such as soldering and that also render contact
resistances unacceptably high in relays and switches. To make soldering easier, coatings of
tin or tin-lead alloys are often applied to copper, and for better contacts overplates of gold are
frequently required. Other surface properties may call for modification; if light reflection is
important, a silver or rhodium plate may be necessary. In wave guides for radar, high
electrical conductivity is the most important criterion, and silver is the preferred coating.
Good bearing properties may require coatings of tin, lead or indium. If a hard surface is
required, chromium or nickel usually will serve. These few examples illustrate another use
of metal finishing; to modify the surface properties, either physical or chemical, to render
them suitable for the intended use.
Although the answer may be obvious, we may pause momentarily to consider this question: if
these coating metals are necessary to provide the article with the desired properties, why go
through the somewhat complicating process of electroplating? Why not simply manufacture
the article out of the desired metal in the first place? Usually the answer is cost or
availability, and, in some cases, the properties of the metals concerned. An all-platinum
chemical reaction vessel of practical production size would be prohibitively expensive; but a
steel vessel, clad with a relatively thing layer of platinum, serves the purpose at far lower
cost. An all-nickel automobile bumper would render the car a luxury for the rich, aside from
the fact that the required amount of nickel would probably be unobtainable. A tin can made
entirely of tin would not only be more expensive than the good inside, but would also have
no physical strength; tin is a very soft and weak metal. Chromium in massive form is almost
impossible to work into useful shapes. In summary electroplating allows the use of relatively
inexpensive metals like steel and zinc for the bulk of the article, while affording to the exterior the selected properties of the coating chosen.