The Chemistry of Painting Cars

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The Chemistry of Painting Cars

It is necessary to paint cars because the paint protects the steel of

the car from corrosion, paint fills and smooths out any imperfections

in the steel surface and it provides a durable, decorative, glossy

appearance.

If rusting continually takes place the car becomes unsafe. When water

and oxygen come in contact with the metal of the car surface, several

redox reactions happen. The oxygen is reduced to hydroxide ions and

iron is oxidized to Fe2+ ions which pass into solution. More reactions

happen which ultimately produce rust - Fe2O3H2O.

The components of car paint

There are three components of car paint, each one has different roles:

* The pigment provides a barrier to protect car from atmosphere

slowing the rate of corrosion. It disguises appearance of the

steel car body, gives colour and other effects which enhance the

appearance of the car.

* The polymers in paint protect the metal from damage that may be

caused by the paint sticking to the surface. It also allows the

paint to have a continuous, unbroken film by flowing under the

effect of surface tension. This gives the car a smooth, glossy

finish.

* The solvent in paint aids the transfer of paint between the

container and the surface (when being sprayed) because the paint

polymer is dissolved in it. The solvent helps the paint flow while

it dries and then evaporates. This causes health and environmental

problems.

When painting cars three different layers of paint are applied. Each

one has a different function.

Layer

Function

Properties

Primer

...

... middle of paper ...

... * Chemical resistance (from cross-linking).

* Adhesive

* Control of flow properties.

References

Fig. 1 The structure of an epoxy resin present in primers.

Taken from "A Perfect Finish"

By Gus Palluel, Vol. 3, No.1, September 1993, Philip Allan Publishers

Fig. 2 The structure of a polymer often present in a surfacer.

Taken from "A Perfect Finish"

By Gus Palluel, Vol. 3, No.1, September 1993, Philip Allan Publishers

[1] "A Perfect Finish"

By Gus Palluel, Vol. 3, No.1, September 1993, Philip Allan Publishers

[2] "'Aquabase' Safeguard the environment - without sacrificing the

finish"

By Graham Wheeler, ICI STEAM Magazine, Issue No. 14, January 1991

[3] Salters Advanced Chemistry - Chemical Storylines

By George Burton, John Holman, Gwen Pilling and David Waddington

[4] "Bonded!"

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