Nace CP 1, Course Manual

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CHAPTER 2
BASIC CHEMISTRY AND BASIC CORROSION THEORY
CP 1 – Cathodic Protection Tester Course Manual
©
NACE International, 2000
02/01/05
Basic Chemistry
Corrosion
is defined by NACE International as the deterioration of a
material, usually a metal that results from a reaction with its environment.
Understanding corrosion and cathodic protection requires a basic
knowledge of chemistry and electrochemistry. Electrochemistry is a branch
of chemistry dealing with chemical changes that accompany the passage of
an electric current, or a process in which a chemical reaction that produces
an electric current. Pertinent terms and descriptions are given in this
chapter.
Elements
All matter is made up of chemical elements. These elements are the
building blocks of the physical world and are composed of atoms. As of
1998 there were 109 recognized elements, some of which have been found
only as products of nuclear reactions and last for only very short periods.
Atoms
An atom consists of a nucleus and orbiting electrons. The nucleus is made
up of positively charged particles called
protons
and neutral particles called
neutrons
. For any given atom, the number of protons equals the number of
negatively charged electrons. Therefore, an atom has no net electrical
charge. See Figure 2.1.