326
Fundamentals of Corrosion
zones where the layer is destroyed by the mechanical stress can block the fissuring attack by inhibiting the anodic process of metal dissolution.
With regard to corrosion fatigue, there are two principal ways to mitigate
the phenomenon: (1) by lowering the stress amplitude or (2) by reducing
the corrosivity of the medium. The latter can be achieved by varying pH,
decreasing temperature, or adding inhibitors.
10.8 Summary
Corrosion inhibitors are usually able to prevent general or uniform corrosion. However, they are very limited in their ability to prevent localized
corrosion such as pitting, crevice corrosion, galvanic corrosion, or stress corrosion cracking. Additional research work is being undertaken in the use of
inhibitors to prevent these types of corrosion. The importance of these studies is realized when it is taken into account that only about 30% of all failures
because of corrosion in chemical plants result from general corrosion. The
remaining 70% is due to stress corrosion cracking, corrosion fatigue, and erosion corrosion. Attack on metals by general corrosion can be predicted and
life spans of the equipment determined and/or the corrosion rates reduced
by the use of inhibitors. This is not the case with other types of corrosion.
The use of inhibitors can be advantageous in certain cases. However, before
using inhibitors, it is essential that the efficiency of the inhibitor to be used
be determined to ensure that inhibition will take place.
References
1. Trabanelli, G. and Carassiti, V., 1970, Advances in Corrosion Science and Technology,
Fontana, M.G. and Staehle, R.W., Eds., Vol. 1, New York: Plenum Press, p.
147–229.
2. Foroulis, Z.H., 1969, Proc. Symp. Basic and Applied Corrosion Research, Houston:
NACE International.
3. Riggs, Jr., O.L., 1973, Corrosion Inhibitors, Nathan, G.C., Ed., Houston: NACE
International, p. 7.
4. Thomas, J.C., 1976, Corrosion, Shreir, J.L., Ed., Vol. 2, London: Newnes
Butterworths, p. 183.
5. McCafferty, E., 1979, Corrosion Control by Coatings, Leidheiser, H., Ed., Princeton,
NJ: Science Press, p. 279.
6. Rosenfield, J.L., 1981, Corrosion Inhibitors, New York: McGraw-Hill.
7. Fisher, H., 1972, Werkst. Korros, 23: 444–465.
Fundamentals of Corrosion
zones where the layer is destroyed by the mechanical stress can block the fissuring attack by inhibiting the anodic process of metal dissolution.
With regard to corrosion fatigue, there are two principal ways to mitigate
the phenomenon: (1) by lowering the stress amplitude or (2) by reducing
the corrosivity of the medium. The latter can be achieved by varying pH,
decreasing temperature, or adding inhibitors.
10.8 Summary
Corrosion inhibitors are usually able to prevent general or uniform corrosion. However, they are very limited in their ability to prevent localized
corrosion such as pitting, crevice corrosion, galvanic corrosion, or stress corrosion cracking. Additional research work is being undertaken in the use of
inhibitors to prevent these types of corrosion. The importance of these studies is realized when it is taken into account that only about 30% of all failures
because of corrosion in chemical plants result from general corrosion. The
remaining 70% is due to stress corrosion cracking, corrosion fatigue, and erosion corrosion. Attack on metals by general corrosion can be predicted and
life spans of the equipment determined and/or the corrosion rates reduced
by the use of inhibitors. This is not the case with other types of corrosion.
The use of inhibitors can be advantageous in certain cases. However, before
using inhibitors, it is essential that the efficiency of the inhibitor to be used
be determined to ensure that inhibition will take place.
References
1. Trabanelli, G. and Carassiti, V., 1970, Advances in Corrosion Science and Technology,
Fontana, M.G. and Staehle, R.W., Eds., Vol. 1, New York: Plenum Press, p.
147–229.
2. Foroulis, Z.H., 1969, Proc. Symp. Basic and Applied Corrosion Research, Houston:
NACE International.
3. Riggs, Jr., O.L., 1973, Corrosion Inhibitors, Nathan, G.C., Ed., Houston: NACE
International, p. 7.
4. Thomas, J.C., 1976, Corrosion, Shreir, J.L., Ed., Vol. 2, London: Newnes
Butterworths, p. 183.
5. McCafferty, E., 1979, Corrosion Control by Coatings, Leidheiser, H., Ed., Princeton,
NJ: Science Press, p. 279.
6. Rosenfield, J.L., 1981, Corrosion Inhibitors, New York: McGraw-Hill.
7. Fisher, H., 1972, Werkst. Korros, 23: 444–465.