Basic Chemistry and Basic Corrosion Theory 2:6
CP 1 – Cathodic Protection Tester Course Manual
© NACE International, 2000
02/01/05
Oxidation and Reduction
Oxidation
Oxidation is the term applied to the loss of one or more electrons from an
atom or molecule, which then forms a positively charged ion. An oxidation
reaction occurs any time electrons are given up by an atom or molecule.
The atom or molecule decreases in negative charge.
For example, when a neutral iron atom (Fe) oxidizes, it may lose two or
three electrons, producing positively charged iron ions (Fe
++
or Fe
+++
), as
shown in Figure 2.5.
Fe → Fe
++
+ 2e
–
Fe → Fe
+++
+ 3e
–
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
ANODE
ELECTROLYTE
Fe°
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
ANODE
ELECTROLYTE
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
Fe
++
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
e
-
ANODE
ELECTROLYTE
Fe°
Figure 2.5 Anodic Process (half reaction)
The electrode or metallic site where oxidation occurs is called an anode.
Note: The term oxidation is not necessarily associated with oxygen.
To Next Page
Loading...