 Failure Analysis
CO2 Corrosion
CO2 combines with water to form carbonic acid that lowers
the pH of the water. Carbonic acid is very aggressive to steel
and results in large areas of rapid metal loss that can completely
erode sucker rods and couplings. The corrosion severity increases
with increasing CO2 partial pressure and temperature. CO2 corrosion
pits are round based, deep with steep walls and sharp edges.
The pitting is usually interconnected in long lines but will
occasionally be singular and isolated. The pit bases will be
filled with iron carbonate scale, a loosely adhering gray deposit
generated from CO2.
 Figures 19 and 20
show typical examples
of CO2 corrosion.
Figure 19 is an example
of CO2 corrosion
on couplings and
Figure 20 is an example
of CO2 corrosion
on rod bodies.
|
