FTB 33102 CORROSION TUTORIAL 1 Question 1: a) Type of corrosion may occur on welded structure of underground gas pipeline is uniform corrosion. Most of the corrosion of underground metal is as a result of an electrochemical reaction. Corrosion occurs through the loss of the metal ions at anodic area to the electrolyte. Cathodic areas are protected from corrosion because of the deposition of hydrogen or other ions that carry current. The sign will show on pipe is just the surface of pipe will corroded and the corrosion will not penetrate through the steel. Cathodic area is not corroded at pipe surface. The current flow through the pipe steel from cathodic area back to anodic area to complete a circuit. At the anodic area, current leave the steel to enter the surrounding earth, steel is being corroded at the surface in anodic area as current flow through earth from anodic to cathodic area. Factor affect underground corrosion: Soil Resistivity Soil resistivity depends on the natural ingredient the amount of salt dissolved in the soil and moisture content. For the cathodic protection applications, galvanic anodes are used generally in those cases where relatively small increments of current are required in areas where soil resistivity is low that enough to permit obtaining the desired current with a reasonable number of anodes. Soil pH Value
Question 1:a) Type of corrosion may occur on welded structure of
underground gas pipeline is uniform corrosion. Most of the
corrosion of underground metal is as a result of an electrochemical
reaction. Corrosion occurs through the loss of the metal ions at
anodic area to the electrolyte. Cathodic areas are protected from
corrosion because of the deposition of hydrogen or other ions that
carry current.The sign will show on pipe is just the surface of
pipe will corroded and the corrosion will not penetrate through the
steel. Cathodic area is not corroded at pipe surface. The current
flow through the pipe steel from cathodic area back to anodic area
to complete a circuit. At the anodic area, current leave the steel
to enter the surrounding earth, steel is being corroded at the
surface in anodic area as current flow through earth from anodic to
cathodic area.Factor affect underground corrosion: Soil
ResistivitySoil resistivity depends on the natural ingredient the
amount of salt dissolved in the soil and moisture content. For the
cathodic protection applications, galvanic anodes are used
generally in those cases where relatively small increments of
current are required in areas where soil resistivity is low that
enough to permit obtaining the desired current with a reasonable
number of anodes. Soil pH ValueThe main factor that affects
underground corrosion process is the soil pH value. The more acidic
the soil is, the higher the corrosion rate.
