Transcript
Influence of Microstructure & Environment on CO CorrosionEnvironment on CO2 CorrosionVicky Indrafusa0806455906
Teknik Metalurgi dan Material FTUI
Introduction
• CO2 and H2S gases in combination with water are the main cause of
corrosion in oil and gas production.
• It results from the practice of pumping CO2 saturated water (seawater
or fresh water) into wells to enhance oil recovery and reduce theor fresh water) into wells to enhance oil recovery and reduce the
viscosity of the pumped fluid.
• As field ages, the ratio of water/oil in the produced fluids increases and
can reach levels of 95% or higher. increase of the corrosion problems.
• Approximately 60% of oilfield failures are related to CO2 corrosion.
• CO2 can produce not only general corrosion but also localized corrosion.
CO2 corrosion basic reactions
Cathodic Reaction
Anodic Reaction
Introduction
• Due to these processes, a corrosion layer is formed on the steel
surface.
• Because of its low solubility, FeCO3 precipitates out of solution.
• The corrosion rate will depend on the properties &• The corrosion rate will depend on the properties &
protectiveness of FeCO3 scale.
• The protectiveness of FeCO3 scale depend on the nature of the
base alloy (microstructure, composition) and on the properties of
the environment (temperature, pH, CO2 partial pressure, etc.).
Objective
• Dari 2 jurnal yang dibahas, akan diamati
karakteristik FeCO3 scale terhadap pengaruh
dari mikrostruktur base metal dan kondisi
lingkungan (pH dan temperatur).
The influence of microstructure of
carbon steels in CO2 corrosion
Introduction
• The aim of the present work is to discuss the effect of carbon steels J55
Grade microstructure on corrosion resistance performance in CO2
environments.
• Microstructure material mempengaruhi characteristics of corrosion layers
(morphology, thickness and composition) yang terbentuk.(morphology, thickness and composition) yang terbentuk.
• Different microstructure is resulted from two different heat treatments
(annealing and quench and tempering).
• The microstructure is considered to have an important effect on how firmly
the corrosion scale sticks to the surface.
• The corrosion layer formed on carbon steel is also composed of cementite
(Fe3C).
Experimental
• The characterization was made by means of scanning
electron microscopy (SEM), electron dispersive X-ray
(EDX) and X-ray photoelectron spectroscopy (XPS).
• The test solution was 5 wt.% of NaCl (analytical-reagent• The test solution was 5 wt.% of NaCl (analytical-reagent
grade), saturated with deoxygenated CO2 at pH 6 and
40oC.
• Sample J55 Grade for both microstructure (F/P and M)
immersed in corrosive media during 144 h, then the
tested sample is characterized.
Result and Discussion
Result and Discussion
Result and Discussion
Result and Discussion
• Electrochemical impedance spectroscopy (EIS) and linear
polarization resistance (LRP) results showed that Q and T samples
present higher resistance polarization (Rp) values and, therefore,
have a better corrosion resistance than the annealed ones.
Conclusion
• The adherence of the scale to the metal depend on the
microstructure of the metal specimen.
• The adherence of the corrosion product film was higher in the
quenched samples.quenched samples.
• From the results, it was concluded that the microstructure of
the steel influences the properties of the corrosion layers, such
as morphology and proportion of the various chemical
compounds present.
The effects of temperature and pH on
the characteristics of corrosion product
in CO2 corrosion of grade X70 steel2
Introduction
• Tujuannya mengamati the effects of environmental
parameters such as temperature and the in situ pH on the
characteristics of iron carbonate film formed on the CO2
corrosion of grade X70 steel.
Experimental procedures
• Samples X70 steel have cylindrical shape with the exposed surface
area of 5.4 cm2.
• The samples polished using SiC papers 60-2000 grit, then
degreased in acetone using an ultrasonic cleaning device.
• The experiments were carried out in a glass cell filled with 2.5 L of• The experiments were carried out in a glass cell filled with 2.5 L of
deionized water and 3 wt.% NaCl at atmospheric pressure in the
temperature range of 55-850C and pH 5.5-6.5 for 72 h.
• Before testing, the solution was deoxygenated by purging CO2 for at
least 2 h.
• CO2 purging was continued throughout test. pH was monitored
throughout the test and adjusted using NaHCO3 or HCl.
Results and discussion
T = 55oC
• At 55oC, from XRD pattern, FeCO3 has not formed on any of the samples.
• 55oC is lower than the threshold temperature for forming FeCO3.
• At 55oC, from SEM image, shows that no corrosion product film was formed
on the surface of steel.
Results and discussion
T = 65oC
• From XRD pattern, FeCO3 has formed in all samples.
• 65oC is equal or higher than the threshold temperature of FeCO3 formation.
• From SEM image, rhombohedric FeCO3 crystals are precipitated in all
samples.
• The apparent compactness of layer ↑ with ↑ pH; the highest compactness
was seen at pH 6.5.
T = 75oC
• From XRD pattern, show that FeCO3 has precipitated in all pH conditions
pH ↑, the number of FeCO3 peaks ↑ the amount of FeCO3 ↑
• Compared to 65oC, at 75oC there are more grains with a compact
arrangement in all pH conditions, which formed an apparently dense layer.
Results and discussion
T = 85oC
• From XRD pattern, it can be seen that the intensities of
characteristic peaks of FeCO3 ↑ with pH ↑, which shows an increase
in the amount of FeCO3.
• From fig. 9 altering pH from 5.5-6 caused FeCO3 grains to get finer,• From fig. 9 altering pH from 5.5-6 caused FeCO3 grains to get finer,
but changing pH from 6-6.5 did not change the grain size.
Results and discussion
Cross section SEM micrograph
• The mean thickness of iron carbonate film was 23 µm at 65oC; it
increased to 32 µm at 75oC and reached 39 µm at 85oC.
Conclusion
• Growth of FeCO3 film is due to the interaction of, the corrosion of steel
and the precipitation of FeCO3.
• For the precipitation of FeCO3, the role of temperature is more
pronounced than that of pH.
• According to both XRD and SEM results it could be concluded that the • According to both XRD and SEM results it could be concluded that the
thickness, compactness and amount of FeCO3 layer has increased with
increasing pH
• In CO2 corrosion of grade X70 steel, the threshold temperature for
forming FeCO3 layer was 65oC below which no carbonate was detected.
• At 65oC in the pH range of 5.5-6.5, iron carbonate phase precipitated as
an apparently porous layer.
Conclusion (2 journal)• Karakteristik (protectiveness) dari FeCO3 scale dipengaruhi oleh
mikrostruktur dari base alloy dan lingkungan (temperature, pH).
• Increasing pH, will increase thickness, compactness and amount of
FeCO3 layer. Corrosion Rate ↓
• There is threshold temperature for forming FeCO3 layer (scaling3
temperature), which below this temperature FeCO3 layer doesn’t
formed.
• Below scaling temperature (i.e. 65oC), the uniform corrosion rate
increases with temperature.
• Above scaling temperature protective films are formed more easily
during increasing temperature. Corrosion Rate ↓
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