Page 18 - Corrosion Engineering Principles and Practice

2 C h a p t e r 1 T h e S t u d y o f C o r r o s i o n 3

With this information an informed decision can be made as to the
type, cost, and urgency of possible remedial measures.
Required levels of maintenance can vary greatly depending on
the severity of the operating environments. While some of the
infrastructure equipment might only require regular repainting and
occasional inspection of electrical and plumbing lines, some chemical
processing plants, power generation plants, and aircraft and marine
equipment are operated with extensive maintenance schedules.
Even the best design cannot be expected to anticipate all condi-
tions that may arise during the life of a system. Corrosion inspection
and monitoring are used to determine the condition of a system and
to determine how well corrosion control and maintenance programs
are performing. Traditional corrosion inspection practices typically
require planned periodic shutdowns or service interruptions to allow
the inspection process. These scheduled interruptions may be costly
in terms of productivity losses, restart energy, equipment availability,
and material costs. However, accidental interruptions or shutdowns
are potentially much more disruptive and expensive.

1.2 The Study of Corrosion
To the great majority of people, corrosion means rust, an almost
universal object of hatred. Rust is, of course, the name which has
more recently been specifically reserved for the corrosion of iron,
while corrosion is the destructive phenomenon which affects almost
all metals. Although iron was not the first metal used by man, it has
certainly been the most used, and must have been one of the first on
which serious corrosion problems were encountered [1].
Greek philosophers viewed the physical world as matter organized
in the form of bodies having length, breadth, and depth that could act
and be acted upon. They also believed that these bodies made up a
material continuum unpunctuated by voids. Within such a universe,
they speculated about the creation and destruction of bodies, their
causes, the essence they consisted of, and the purpose they existed for.
Surfaces did not fit easily into these ancient pictures of the world, even
those painted by the atomists, who admitted to the existence of voids.
The problem of defining the boundary or limit of a body or between
two adjacent bodies led Aristotle (fourth century BC) and others to
deny that a surface has any substance. Given Aristotle’s dominance in
ancient philosophy, his view of surfaces persisted for many centuries,
and may have delayed serious theoretical speculation about the nature
of solid surfaces [2].
Perhaps the only ancient scientific account of surfaces is to be
found in some passages of the great Roman philosopher Pliny the
Elder (23–79 AD) who wrote at length about ferrum corrumpitur, or
spoiled iron. By his time the Roman Empire had been established as
the world’s foremost civilization, a distinction due partly to the