C h a p t e r 2
While designers are frequently concerned
about water and its effects on electrical
systems, other processes are at work. One
such process is corrosion, in which water
plays a crucial role. Iron oxide, otherwise
known as rust, is formed in the presence
of water and oxygen. Connectors use iron
or steel, but oxidation is not limited to
ferrous materials.
In some metals, oxidation forms a hard
layer on the surface, which prevents
further damage. Stainless steel behaves
in this way; connectors intended for
exposed conditions are often constructed
of stainless steel.
Other metals are also subject to corrosion.
Aluminum and its alloys are frequently
used to construct connector shells. The
combined strength, light weight, and
electrical conductivity of aluminum makes
it a popular choice for the aerospace
industry. Aluminum bonds readily with
oxygen, forming a layer of aluminum oxide,
which protects the body of the connector
underneath. However, aluminum oxide is
vulnerable to corrosive chemicals.
Rainwater, with its everyday contaminants,
is slightly acidic, with a pH value of
around 5.5. This acidity level is not
enough to damage the aluminum oxide
layer, but acid rain, which is contaminated
with other chemicals, will damage the
surface layer. Similarly, seawater, which
has a pH value of 8 (slightly alkaline), will
cause an aluminum surface to rapidly
CHEMICALS AND CORROSION
Naresh Radaliyagoda
Test Engineer, Vestas
The wind industry is a great
example of a harsh environment
where components must operate
in challenging conditions, like
offshore locations with corrosive
conditions, cold climates with
freezing temperatures, and desert
regions with fine dust and extreme
temperature fluctuations."
11
Understanding Harsh Environments for Electronic Design
