Forms of Metallic Corrosion
55
6. Microbiological methods
7. Physical methods
Before any remedial action can be taken, it is necessary to identify the type
of bacteria involved in the corrosion. Aeration of water in a closed recirculating system reduces the activity of anaerobic bacteria. Chlorination and treatment with biocides help control populations of some bacteria, although they
are not effective in all cases. Also, the bacteriocides fail to reach the areas
underneath deposits where the bacteria thrive. Coating a buried structure
with tar, enamel, plastic, or the like is often an effective means to preclude
bacteria from the metal surface. Cathodic protection in combination with
coatings can be used to prevent or arrest MIC.
During storage or after hydrotesting, water should not be allowed to stand
for a long period of time. Complete drainage and drying is advised. Inhibitors
may be used in stagnating water and cutting-oil fluids. Periodic cleaning of
pipelines is also essential. In most affected soils, steel pipes may be replaced
by plastic pipes to avoid microbiological corrosion.
In areas where macrofouling may occur, these options can reduce or prevent fouling. The application of antifouling paints is probably the most effective and widely used means of preventing biofouling in seawater. Ships and
piers are coated with specially formulated paints containing compounds toxic
to the organisms. Copper compounds are often used because their released
copper ions poison the growth of barnacles and other marine organisms.
Periodic cleaning of the surfaces of structures and the inside of pipelines helps
reduce the growth of crevice sites. In closed systems, fouling can be mitigated
by chlorination and periodic injection of suitable biocides, including copper
compounds.
The approach to follow depends on the type of bacteria present. A technique that has gained importance, in addition to the preventive method, is
that of a simulation of biogenic attack. A quick-motion effect can be produced that will allow materials to be tested for their compatibility for a specific application. To conduct the simulation properly, it is necessary that a
thorough knowledge of all the processes and participating microorganisms
be known. The situation may be modified under conditions that will be optimal for the microorganisms, resulting in a reduced time span for the corrosion to become detectable.
3.9 Selective Leaching
The removal of one of the components of an alloy by corrosion is termed
“selective leaching.” Dezincification is the term used to describe the leaching
55
6. Microbiological methods
7. Physical methods
Before any remedial action can be taken, it is necessary to identify the type
of bacteria involved in the corrosion. Aeration of water in a closed recirculating system reduces the activity of anaerobic bacteria. Chlorination and treatment with biocides help control populations of some bacteria, although they
are not effective in all cases. Also, the bacteriocides fail to reach the areas
underneath deposits where the bacteria thrive. Coating a buried structure
with tar, enamel, plastic, or the like is often an effective means to preclude
bacteria from the metal surface. Cathodic protection in combination with
coatings can be used to prevent or arrest MIC.
During storage or after hydrotesting, water should not be allowed to stand
for a long period of time. Complete drainage and drying is advised. Inhibitors
may be used in stagnating water and cutting-oil fluids. Periodic cleaning of
pipelines is also essential. In most affected soils, steel pipes may be replaced
by plastic pipes to avoid microbiological corrosion.
In areas where macrofouling may occur, these options can reduce or prevent fouling. The application of antifouling paints is probably the most effective and widely used means of preventing biofouling in seawater. Ships and
piers are coated with specially formulated paints containing compounds toxic
to the organisms. Copper compounds are often used because their released
copper ions poison the growth of barnacles and other marine organisms.
Periodic cleaning of the surfaces of structures and the inside of pipelines helps
reduce the growth of crevice sites. In closed systems, fouling can be mitigated
by chlorination and periodic injection of suitable biocides, including copper
compounds.
The approach to follow depends on the type of bacteria present. A technique that has gained importance, in addition to the preventive method, is
that of a simulation of biogenic attack. A quick-motion effect can be produced that will allow materials to be tested for their compatibility for a specific application. To conduct the simulation properly, it is necessary that a
thorough knowledge of all the processes and participating microorganisms
be known. The situation may be modified under conditions that will be optimal for the microorganisms, resulting in a reduced time span for the corrosion to become detectable.
3.9 Selective Leaching
The removal of one of the components of an alloy by corrosion is termed
“selective leaching.” Dezincification is the term used to describe the leaching