Page 45 - Science Class 08

vehicles, bridges, household appliances like with grease. Cycle-chains are greased in order
washing machine, refrigerators, etc. are coated to save them from rust that hampers their
with paint sprays. It is done to save them from smooth func oning.
corrosion. Galvanising

Electropla ng It is somewhat like electropla ng. The surface

In this process, metals like iron and steel are of the metal is thoroughly cleaned and dipped
covered with a thin coa ng of chromium and into melted zinc. Iron sheets to be used for
n as these metals are an corrosion. roofing, buckets, pipes, drums and trunks are
Electropla ng is used in the case of utensils, galvanised to keep off corrosion.
steel furniture, handles of bicycles and taps.
Electropla ng provides the metal with a good

shine, saves it from corrosion and also gives it a
longer life.
– +
e – e –

Cathode (+) Anode (–)
Me Cu

Galvanising
Cu

Cu 2+
The word— NOBLE means non-reac ve in
2–
So 4 chemistry. We come across two terms in
chemistry with the use of this word
Electropla ng
—noble— as an adjec ve.
Alloying
1. NOBLE GASES : They are six in number
Some metals when alloyed with other metals
and generally, they do not react with
become an -corrosion. Iron, when alloyed with other materials. They are helium, neon,
carbon, nickel and chromium, forms stainless argon, xenon, krypton and radon. The
steel that never rusts. only compounds that three of these

Greasing gases — xenon, krypton, radon — form
when they combine with fluorine.
A thick coat of oil or grease also makes a metal
an -corrosion as these things keep air and 2. NOBLE METALS : These innert metals are
moisture off its surface. Brand new tools like silver, gold and pla num. They are very
scissors, knives and screw drivers are smeared costly metals.

Malleable : Able to be hammered or pressed into shape without breaking
Ductile : Able to be drawn out into a thin wire

Oxidation : The process or result of oxidising or being oxidised

Science-8 45