zslhnxx
第18楼2006/10/26
Billions of dollars are spent each year on the prevention of iron corrosion. Corrosion converts
steel, an extremely strong, cheap and versatile building material composed of iron and carbon,
into brittle iron oxides known as rust. The problem is compounded as rust tends to scale off the
surface of iron, exposing more iron to the oxidising environment. This is in contrast to some
other metals, such as aluminium where an oxide coating offers a degree of passivation,
preventing further corrosion.
When iron is placed into a deoxygenated acidic solution, the following reactions are established.
zslhnxx
第19楼2006/10/26
However, jcorr and hence the rate of corrosion per unit area can be determined indirectly using
potentiodynamic polarization, the limiting form of the Butler-Volmer equation (Equation 2.1)
and Tafel plots.
j = j
0
e
(1-)f- e -f { }
where f =
nF
RT
, = E
applied
- E
corr
= transfer coefficient
The first exponential term in Equation 2.1 corresponds to the anodic component whilst the
second is the cathodic component.
……(2.1)
zslhnxx
第20楼2006/10/26
However, jcorr and hence the rate of corrosion per unit area can be determined indirectly using
potentiodynamic polarization, the limiting form of the Butler-Volmer equation (Equation 2.1)
and Tafel plots.
j = j
0
e
(1-)f- e -f { }
where f =
nF
RT
, = E
applied
- E
corr
= transfer coefficient
The first exponential term in Equation 2.1 corresponds to the anodic component whilst the
second is the cathodic component.
……(2.1)