To of hydrocarbon fluids are transported, namely pipe,

To begin with, before
giving detailed information about the reasons of corrosion there is a need to
stress that pipeline is not consists of pipes only. Pipeline is just
combination of all facilities joining to the main line: all parts, including
branches, physical facilities by means of which all types of hydrocarbon fluids
are transported, namely pipe, valves, compressor units, pump stations, metering
stations, regulator stations, delivery stations holders and fabricated
assemblies which comprises pipeline altogether.

There are many factors which can not be
undermined, lead to corrosion, so in order to minimize or prevent the
destructive power of corrosion, considerable steps should be taken. The factors
that lead to corrosion are the material itself and environment for it called
medium (sea, air, soil) where it is expected to take place. It can also be
associated with mechanical, chemical or environmental factors as well as human
activities. The other considerable reasons that may lead to corrosion are
facility age, poor functional performance because of deterioration and not
properly design as well as the nature of materials which it contains.

When the material used for preparation of facility is
near or at the last stage of its demanded useful life, corrosion is highly
probable to occur because at this time materials’ properties are deteriorated because
of long usage.

One of the main factors that affects the corrosion
rate is the nature of the material, since some materials are more vulnerable
and less resistant to other material properties (corrosivity, salinity, oxygen
content etc.) so in terms of their usage, the stage at which corrosion occurs
would be defined. The physical and chemical factors of place should also be
considered where an oil and gas facility is located; so while discussing about
corrosion, material selection 1 should be considered carefully regarding with
the material’s mechanical and chemical resistance. For example, before
construction pipeline in seawater, the factors below should be considered:

·        
General and
localized corrosion rate under steady state condition

·        
Possibility of
crevice corrosion occurrence and pitting especially under stagnant moving
condition

·        
Resistance to
stress corrosion cracking

·        
Effect of seawater
composition, such as salinity, oxygen content and other pollutants

In addition to necessary
medium-environment (air, water, soil), corrosion is created by mainly the
reasons given below associated with production or transportation of
hydrocarbons.