Metals are probably the most significant
discovery by mankind. The world we live in is possible because we know how to
extract & process metals, and build things using them. The biggest enemy in
this process is Corrosion And Rust which gives major setbacks to the economies
of nations across the world. The remedy is Protective Coating to Prevent Corrosion using effective rust preventive oils, waxes, and
other corrosion prevention solutions. But let’s first understand how corrosion sabotages
metal’s life and what makes rust different from corrosion.
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Metals and Corrosion
Cycle
Copper and precious metals like gold,
silver, platinum, etc. are found in nature in their original metallic state. All
other metals including iron & aluminium are processed from ores into metals
that are naturally unstable in their environments. All man-made metals are
unstable and have the tendency to get back into their original stable mineral
state. Some metals form protective passive films like aluminium & copper on
their surfaces and these prevent, or slow down, the corrosion process. Corrosion prevention and control on metals occur because metals are used in an environment where they
are chemically unstable.
Some metals corrode faster than others in galvanic series
The galvanic series determines the electrochemical potential and nobility of metals and metal alloys. Each alloy or metal has a distinctive corrosion potential. The more negative a metal or alloy is (less noble), the more likely it is to suffer galvanic corrosion.
Difference
between Corrosion & Rust:
Corrosion: Corrosion Prevention is the process of deterioration of metals
due to chemical or electrochemical reactions. Corrosion Protection results in the
formation of the oxides of metal or salts. The metal reacts with their surrounding environment,
and over time, lose its defining properties and structure like strength
& appearance. Metals when exposed to the environment undergo oxidation and
react with the oxygen present in the atmosphere. The other factors that cause corrosion
are moisture, salts, acids, bases, and other chemicals. Corrosion also occurs
when metals are exposed to gases like acid vapours, formaldehyde gas, ammonia
gas, and sulfur-containing gases. Some materials are resistant to corrosion,
while some are prone to corrosion. Prevention of corrosion of metals
is possible. The advent of advanced technology including water-based rust
preventives and eco-friendly rust preventive oils has
proved effective against corrosion and rust prevention.
Rust: Though corrosion
and rust are often used interchangeably, rusting is a form of corrosion,
but it specifically refers to the oxidation of iron or its alloys. Only iron
oxide is formed when rusting takes place either in the iron itself or in steel. In the
presence of moisture & oxygen, iron undergoes a chemical or an electrochemical
reaction and forms iron oxide. The colour of iron oxide is generally reddish-brown.
When rusting starts happening at any part of the metal, it gradually spreads,
leaving the entire metal piece completely destroyed.
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Corrosion in aluminium: a thin layer of aluminium oxide forms over the surface of the metal, which acts as a protective barrier. This barrier does not flake off like rust does, which prevents further corrosion of the aluminium. |
Corrosion
in copper, brass, bronze,
and similar metals: it produces
a green colour protective barrier is known as patina.
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