Although over 30 years have now passed since impregnation
began to play an important everyday role in industry,
generally there is still little known as to arguments
for and against the various impregnation systems.
By "knowing the facts" a better judgment
can be made enabling the right choice for the right
reasons. The information compiled in this brochure
has been carefully assembled so as to be factual
and informative.
We acknowledge that whilst other impregnants such
as epoxies, phenolics and polyester resins have
made their mark in the history of impregnation,
their use is now rare, therefore we have concentrated
on the two main systems in use today - namely Sodium
Silicate and Acrylic Sealants (Ultraseal PC 504)
To understand the process of impregnation, it is
equally important to understand the problem - 'Porosity'........
For a long time engineers have been aware of the
problems caused by cavities in metal castings. The
high magnification photograph on the front cover
shows a typical example of such cavities. The problems
caused from porosity defects are many; the main
concern is the porosity across the wall of the casting
allowing liquid or air to pass through it.
As is known, porosity originates when the metal
is cast, particularly in the manufacture of intricate
alloy castings. In addition to gassing and the formation
of air bubbles within the metal structure, it is
in the cooling down of the metal when shrinkage
cracks and cavities are formed. The majority of
castings produced contains such defects and are
often undetected by the naked eye.
porosity in casting can be divided into three categories
Fully Enclosed
Blind
Porosity
Through porosity
A problem only if opened
up by machinery operations.
Can causespotting out of planing &
blowout of paint finishes.
Which will allow the passage
of liquid or air through the wall
Living with Porosity - Knowing the facts
