substituted phenols andn aphthols, b -diketones, 8-hydroxyquinoline,
and quinalizarin.
3.7T emporary Protection with Inhibitors
Occasions arise when temporaryp rotection of metallic surfaces against
atmospheric corrosion is required. Typical instances are in the case of
finished metallic materials or of machinery parts during transportation
and/ors torage prior to use. When ready for use, the surface treatment or
protective layer can be easily removed.
It is also possibletoprovide protection by controlling the aggressive gases
or by introducing avapor phase inhibitor.Thislatter procedure can only be
accomplished in ac losed environment sucha ss ealed containers,m useum
showcases, or similar enclosures.
Organic substances used as contact inhibitors or vapor inhibitors are
compounds belonging to the following classes:
1. Aliphatic, cycloaliphatic, aromatic, and heterocyclic amines
2. Amine salts with carbonic, carbamic, acetic, benzoic, nitrous, and
chromic acids
3. Organic esters
4. Nitro derivatives
5. Acetylenic alcohols
3.8I nhibitiono fL ocalized Corrosion
Corrosion inhibitors are usually able to prevent general corrosion, but their
effect on localizedc orrosion processes is limited.
31
Generally,ahigher
inhibitor concentration is required to prevent localized corrosionp rocesses
than is necessary to inhibit general corrosion.
Staehle
32
examined the possibility of inhibiting localizeda ttack that
does notd ependo nm etallurgical structures.H ec onsideredp henomena
relatedto:
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 efficiento n
Corrosion Inhibitors
65
CAT8247—CHAPTER 3—6/10/2006—19:23—KADAMBADI—XMLMODEL B–p p. 55–68
and quinalizarin.
3.7T emporary Protection with Inhibitors
Occasions arise when temporaryp rotection of metallic surfaces against
atmospheric corrosion is required. Typical instances are in the case of
finished metallic materials or of machinery parts during transportation
and/ors torage prior to use. When ready for use, the surface treatment or
protective layer can be easily removed.
It is also possibletoprovide protection by controlling the aggressive gases
or by introducing avapor phase inhibitor.Thislatter procedure can only be
accomplished in ac losed environment sucha ss ealed containers,m useum
showcases, or similar enclosures.
Organic substances used as contact inhibitors or vapor inhibitors are
compounds belonging to the following classes:
1. Aliphatic, cycloaliphatic, aromatic, and heterocyclic amines
2. Amine salts with carbonic, carbamic, acetic, benzoic, nitrous, and
chromic acids
3. Organic esters
4. Nitro derivatives
5. Acetylenic alcohols
3.8I nhibitiono fL ocalized Corrosion
Corrosion inhibitors are usually able to prevent general corrosion, but their
effect on localizedc orrosion processes is limited.
31
Generally,ahigher
inhibitor concentration is required to prevent localized corrosionp rocesses
than is necessary to inhibit general corrosion.
Staehle
32
examined the possibility of inhibiting localizeda ttack that
does notd ependo nm etallurgical structures.H ec onsideredp henomena
relatedto:
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 efficiento n
Corrosion Inhibitors
65
CAT8247—CHAPTER 3—6/10/2006—19:23—KADAMBADI—XMLMODEL B–p p. 55–68