324
Fundamentals of Corrosion
accomplished in a closed environment such as sealed containers, museum
showcases, or silmiar enclosures.
Organic substances used as contact inhibitors or vapor inhibitors are compounds belonging to the following classes:
1. Aliphatic, cycloaliphatic, aromatic, and hetrocylic amines
2. Amine salts with carbonic, carbamic, acetic, benzoic, nitrous, and
chromic acids
3. Organic esters
4. Nitro derivatives
5. Acetylenic alcohol
10.7 Inhibition of Localized Corrosion
Corrosion inhibitors are usually able to prevent general corrosion but their
effect on localized corrosion processes is limited. Generally, a higher inhibitor concentration is required to prevent localized corrosion processes than is
necessary to inhibit general corrosion.
Staehle 25 examined the possibility of inhibiting localized attack that does not
depend on metallurgical structures. He considered phenomena related to:
Geometric effects, such as galvanic corrosion and crevice corrosion
•
Simple localization of the attack, such as pitting and dezincification
•
Effects of relative motion, such as erosion and cavitation
•
The application of organic inhibitors to control galvanic corrosion presents
several problems. It is well known that an inhibitive treatment efficient on a
single metal, because of the specific action of the inhibitor, may fail to control corrosion if dissimilar metals are in contact. The behavior of a zinc-steel
couple in sodium benzoate solution was studied by Brasher and Mercer. 26 Steel
is protected in benzoate solution but usually it corrodes when coupled to zinc,
as in galvanized iron, in that solution. An interpretation of the phenomena
was given, emphasizing that rusting of steel coupled to zinc in benzoate solution can be prevented by bubbling air through the solution for 1 or 2 days
immediately after immersion. After this time, the system should have become
stabilized and no corrosion of the steel should take place when the air stream
is discontinued. In the study of the steel-copper combination in a hot-water
system, the best inhibitor efficiency was obtained using a mixture of benzoate
and nitrite.
Fundamentals of Corrosion
accomplished in a closed environment such as sealed containers, museum
showcases, or silmiar enclosures.
Organic substances used as contact inhibitors or vapor inhibitors are compounds belonging to the following classes:
1. Aliphatic, cycloaliphatic, aromatic, and hetrocylic amines
2. Amine salts with carbonic, carbamic, acetic, benzoic, nitrous, and
chromic acids
3. Organic esters
4. Nitro derivatives
5. Acetylenic alcohol
10.7 Inhibition of Localized Corrosion
Corrosion inhibitors are usually able to prevent general corrosion but their
effect on localized corrosion processes is limited. Generally, a higher inhibitor concentration is required to prevent localized corrosion processes than is
necessary to inhibit general corrosion.
Staehle 25 examined the possibility of inhibiting localized attack that does not
depend on metallurgical structures. He considered phenomena related to:
Geometric effects, such as galvanic corrosion and crevice corrosion
•
Simple localization of the attack, such as pitting and dezincification
•
Effects of relative motion, such as erosion and cavitation
•
The application of organic inhibitors to control galvanic corrosion presents
several problems. It is well known that an inhibitive treatment efficient on a
single metal, because of the specific action of the inhibitor, may fail to control corrosion if dissimilar metals are in contact. The behavior of a zinc-steel
couple in sodium benzoate solution was studied by Brasher and Mercer. 26 Steel
is protected in benzoate solution but usually it corrodes when coupled to zinc,
as in galvanized iron, in that solution. An interpretation of the phenomena
was given, emphasizing that rusting of steel coupled to zinc in benzoate solution can be prevented by bubbling air through the solution for 1 or 2 days
immediately after immersion. After this time, the system should have become
stabilized and no corrosion of the steel should take place when the air stream
is discontinued. In the study of the steel-copper combination in a hot-water
system, the best inhibitor efficiency was obtained using a mixture of benzoate
and nitrite.