358
Fundamentals of Corrosion
Design improvements. Design improvements can entail changes to the process conditions. Studies of the mechanism of corrosion can result in the use
of more expensive material in the areas of the corrosion rather than the complete vessel. In dead, or no-flow conditions, the use of a neutral or inert nitrogen gas purge may save a relief valve or other items from corroding. The
selection of the feedstock without certain corrosive impurities may prove to
be the most economical answer.
Specifications for purchasing and/or contractors. Better specifications will
result by the use of the findings of various associations such as NACE, as
was discussed previously under linings and the surface preparation conditions. Materials selection also entails materials with properties within specified guidelines.
Regular inspection and improved techniques. Concerning inspection, zinc-rich
primers under coatings offer long, maintenance-free life providing there
is continuous inspection and patch repair. The zinc-rich primers are either
organic or inorganic. The application depends on the specifications for the
surface preparation and various restrictions during the application. The use
of zinc-rich primers with various topcoats usually requires cathodic protection for localized breaks in the primer over the metal. The aggressiveness
of the environment for a particular zinc primer must be balanced with the
frequency of repair. In an aggressive atmosphere, even the most protective
coating system installed with the finest specifications requires continuous
inspection. The better the system, the less frequent and smaller the amount
of repairs. A protective coating system in a strong chemical environment
should not be expected to last indefinitely.
11.3.3.2 Petroleum Refining Industry
The petroleum refining industry uses sweet or sour crude (contains H 2 S) in
the various operating units to be described in greater detail in this section.
These units in a refinery will be handling saturated and unsaturated hydrocarbons under both high and low temperature and pressure conditions. In
the processing of the crude oil, the refinery will use either a sea, brackish, or
ordinary water system; various purities and pressures of steam and condensate return; hydrogen, acid, and furfural to sweeten lubrication oil and other
petroleum products; ammonia, and caustic.
Design prevention or reduction methods against corrosion for refineries include:
1. Materials selection
2. Crude selection and corrosivity
3. Use of pretreatment of the crude oil
4. Use of corrosion inhibitors
Fundamentals of Corrosion
Design improvements. Design improvements can entail changes to the process conditions. Studies of the mechanism of corrosion can result in the use
of more expensive material in the areas of the corrosion rather than the complete vessel. In dead, or no-flow conditions, the use of a neutral or inert nitrogen gas purge may save a relief valve or other items from corroding. The
selection of the feedstock without certain corrosive impurities may prove to
be the most economical answer.
Specifications for purchasing and/or contractors. Better specifications will
result by the use of the findings of various associations such as NACE, as
was discussed previously under linings and the surface preparation conditions. Materials selection also entails materials with properties within specified guidelines.
Regular inspection and improved techniques. Concerning inspection, zinc-rich
primers under coatings offer long, maintenance-free life providing there
is continuous inspection and patch repair. The zinc-rich primers are either
organic or inorganic. The application depends on the specifications for the
surface preparation and various restrictions during the application. The use
of zinc-rich primers with various topcoats usually requires cathodic protection for localized breaks in the primer over the metal. The aggressiveness
of the environment for a particular zinc primer must be balanced with the
frequency of repair. In an aggressive atmosphere, even the most protective
coating system installed with the finest specifications requires continuous
inspection. The better the system, the less frequent and smaller the amount
of repairs. A protective coating system in a strong chemical environment
should not be expected to last indefinitely.
11.3.3.2 Petroleum Refining Industry
The petroleum refining industry uses sweet or sour crude (contains H 2 S) in
the various operating units to be described in greater detail in this section.
These units in a refinery will be handling saturated and unsaturated hydrocarbons under both high and low temperature and pressure conditions. In
the processing of the crude oil, the refinery will use either a sea, brackish, or
ordinary water system; various purities and pressures of steam and condensate return; hydrogen, acid, and furfural to sweeten lubrication oil and other
petroleum products; ammonia, and caustic.
Design prevention or reduction methods against corrosion for refineries include:
1. Materials selection
2. Crude selection and corrosivity
3. Use of pretreatment of the crude oil
4. Use of corrosion inhibitors