Paints and
Paint Systems
In general, to protect and beautify metal structures, a
multi-coat system of primer, under coat and finish coat
is required. The primer is applied direct to the steel,
the under or intermediate coat builds up the protective
layer and the finish for provides weather resistance.
Each coat has a specific purpose, and is specially
formulated but all paints are made from three basic
components :
- Pigment - in primers
is used to control chemical reactions on the
surface of the metal and also to deal with
moisture in intermediate and finishing coats is
used to improve covering or opacity and to impart
colour
- Medium - binds with
the pigment after the solvent has evaporated and
plays the dominant role in preventing corrosion
- Solvent - or
thinners, evaporates after application
The exception to this general form is Micaceous Iron
Oxide or MIO paints. When micaceous haematite is used as
the pigment in a paint system, it substantially improves
the protective action of the medium and also considerably
extends the life of the system.
What is
Micaceous Haematite?
The material produced by the 'Shiny Ore' mines, is an
almost pure oxide of iron, with the chemical formula of
Fe203. The main difference between this and common
haematite, which is a source of the metal iron, is the
structure of the oxide crystals. When viewed under a
microscope they resemble the structure of mica, hence the
term 'micaceous'. It is this property coupled with its
chemical inertness which makes it ideal for use in paint.
How does
the MIO paint work?
When the paint is applied to a surface, the haematite
flakes orientate themselves, during the drying or curing
process, into layers more or less parallel to the
surface. This results in interleaving and overlapping
somewhat similar to fish-scales or roof tiles, resulting
in a tight seal which acts as an effective barrier to
corrosion from sea - spray, sulphur dioxide, ammonia and
other pollutants. Moisture and oxygen, the primary cause
of rust, cannot permeate the packed, layered structure of
the paint.
The haematite also reinforces the paint in a way rather
like steel reinforcing bars in concrete, and acts as a
sun block shielding the medium. This reduces the tendency
of the paint to crack, craze and blister, maintaining the
protective action of the medium.
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