dd laboratory test to examine effectiveness of Corrosion Inhibitor in welding zone and in the under deposit area.

1. CORROSION
INHIBITOR SELECTION
BONY BUDIMAN
OCTOBER 2020

2. OBJECTIVE AND SCOPE
• Provide general information in Corrosion Inhibitor selection by consider the function,
effect to contact material, field process and effect to environment.
• This is not a formal guideline.A further study shall be carried out to determine the
specific formal guideline.
• The selection list subject to adjust, add or remove depend on budget, previous
experience and the field condition,
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3. QUALIFICATION
TEST
Compatibility
Material Fluid
Stability
Storage
Field
Condition
Performance
Efficiency Properties
Environment
Toxicity Biodegradability Bioaccumulation
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4. COMPATIBILITY
• Material Compatibility
• Metal
• Non Metal
• Fluid Compatibility
• Production Fluid
• Chemical
Courtesy picture :https://www.element.com/materials-testing-services/polymer-testing-services/polymer-chemical-resistance-testing
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5. MATERIAL COMPATIBILITY - DEFINITION
• A series of tests should be carried out utilizing the CI and a variety of specimens that may contact
from the storage tank, daily tank, injection line, injection point and pipeline-flowline.
• Testing should focus first on the highest expected temperature to assess possibility of attack in the
most aggressive environment.
• The metal material could be as carbon steel, stainless steel, cooper, or alloys.
• The non metal material could be as plastic, rubber or composite.
Compatible means the CI will not react significantly or resulting negative effect with the
contacted material
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6. MATERIAL COMPATIBILITY - PROCEDURE
• A specimen of material immersed in the Corrosion Inhibitor (could be neat or as
solution in liquid).
• Keep the test solution at the specified temperature. Exposure times of 1 to 3 weeks are
recommended
• For metal, the test parameter is the corrosion rate
• For non metal, the test parameter are tensile strength, dimension change and
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7. FLUID COMPATIBILITY - DEFINITION
• The compatibility of CI shall be check with any fluid that may contacted such as produced fluid or others
chemicals
• Produced fluid especially with produced water and liquid hydrocarbon
• Compatibility shall be observed between CI and any chemicals that injected in the same line and has
possibility to contact each other
• Observed parameter : change of color, precipitation, emulsion, heat increase, chemical change (by finger
print test)
Compatible means the CI will not react significantly or resulting negative effect with the
other fluid.
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8. STABILITY - DEFINITION
The stability could be in two conditions :
• Storage : consider storage at warehouse or at field,
is the container exposed to direct sunlight ?
• Field Condition : consider the highest temperature
and pressure that exposed to the CI, where the CI
will be injected ? Is the viscosity will be critical
point (for example if the CI will injected through
umbilical to deep water).
Courtesy picture :https://www.atago.net/en/databook-viscosity_principle.php
Stability means that the properties of CI not significant changes under certain condition.
The properties could be phase separation, color, viscosity, pour point and effectiveness
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9. STABILITY - PROCEDURE
• Conduct the respective test for the CI before
exposed at specified temperature and pressure
• Put sample at condition at storage or field
condition
• Re-analysis the same parameter. Notify for any
changes.
• Observed parameter : change of color, phase
separation, viscosity, chemical change (by finger
print test), etc
• Specification may be determine by considering
the field condition and equipment limitation
design.
• An example table shown in the left
No Parameter Initial After 2 weeks,
15oC, 25 bar
Specification
1 Color Yellow to
Brown
Yellow to
brown
Yellow to dark brown
2 Phase 1 phase 1 phase 1 phase
3 Viscosity
(cps)
15 45 Max 25
4 % Inhibition 92.1 % 91.8% Min 90
----
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10. PERFORMANCE TEST
• Properties
• Oil-Water Partitioning
• Solubility
• Emulsion
• Foaming
• Film Persistency
Performance conducted to evaluate the function of chemical to inhibit corrosion
(efficiency) and effect to the produced fluid due to its physical properties.
• Efficiency
• Weigh Loss Method
• Static ImmersionTest
• WheelTest
• Rotating Cage
• Electric Current Method
• Bubble Test
• Rotating Cylinder Electrode Test
• Flow Loop Test
• Jet Impingement Test
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11. EFFICIENCY
• Efficiency means how effective the CI in the fluid could inhibit corrosion rate compare to non
treated fluid.
• The corrosion rates can be measured using mass loss or electrochemical methods.
• Using the methodologies, several variables, compositions of material, composition of
environment (gas and liquid), temperature, pressure, and flow, that influence the corrosion
rate in the field can be simulated in the laboratory.
• The performance of a corrosion inhibitor is influenced primarily by the nature of inhibitor,
operating conditions of a system, and the method by which it is added. The lab tests shall
consider this such as the temperature, pressure, shear stress, oil-water composition, corrosive
gas concentration (CO2 and H2S) and ions composition in the brine water.
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12. STATIC IMMERSIONTEST
• The working principle of this method is by calculate metal loss of
metal coupon before and after the test. More metal loss means
more corrosive.
• This is a basic test for other weigh loss test such as wheel test and
rotating cage.
• Coupons were weighed and fully immersed in triplicate in 200ml
of the various test solution for a period of 100 hrs.After the set
intervals of time, the metal coupons were wiped with cotton
damped with trichloroethylene for removal of the excess oil.Then
the specimens were cleaned with respective solutions as per
ASTM G1-90.
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13. WHEELTEST
• The working principle of this method is by
calculate metal loss of metal coupon before and
after the test.
• The method is an enhance of immersion static
test by add variable of dynamic flow.
• The pre-weight metal coupon immersed in the
corrosive liquid, in the tight capped glass bottle.
• The bottle is then rotated at a certain
temperature and time.
• At the end, the coupon re-weight. Loss of
weight then calculate to % inhibition
Courtesy picture : https://www.techboxsystems.com/corrosion-wheel-test-2/
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14. ROTATING CAGE (RC)
• The working principle of this method is by calculate metal loss of
metal coupon before and after the test
• RC provides higher flow velocities than can usually be obtained
simply by stirring the solution.
• RC is a promising and reliable method to simulate pipeline flow
under laboratory conditions by rotating the specimens at speeds
upto 1500 rpm
• Advantage of RC inexpensive, compact, hydro dynamically
characterized and provides various flow conditions
Courtesy picture : https://shodhganga.inflibnet.ac.in/bitstream/10603/13315/7/07_chapter%203.pdf
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15. BUBBLETEST
• The working principle of this method is by
measure the electric current density in solution.
The higher the current density that arises, the
more severe the corrosion will be and vice versa
• The bubble is the quickest test and the most
convenient as first screening test; it is conducted
with magnetic stirring of the test solution, without
control of the shear stress
• This is a basic method for others electric current
density method such as RCE and JIT
Courtesy picture : https://www.sciencedirect.com/science/article/abs/pii/S0920410514000965 and
http://www.acminstruments.com/support/techniques/bubble-test and
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16. ROTATING CYLINDER ELECTRODE (RCE) TEST
• The working principle of this method is by measure the electric
current density in solution.The higher the current density that
arises, the more severe the corrosion will be and vice versa
• This method simulates the flowing fluid conditions
• Using a cylindrical electrode that continues to rotate
• The advantage of this method can also see the effect of fluid
velocity on the CI filming properties
• The RCE test system is compact, relatively inexpensive, and easily
controlled). It operates in the turbulent regime over a wide range
of Reynolds numbers.
Courtesy pictures : https://www.researchgate.net/figure/The-setup-of-the-rotating-cylinder-electrode-RCE_fig2_256913871 and
https://pineresearch.com/blog/researchers-corrosion-electrochemistry/
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17. FLOW LOOP TEST
• The most expensive, is the test better reproducing the
field conditions for corrosion inhibition.
• An experimental pipe that contains various corrosion
probes to monitor corrosion rates.
• Flow loops are used to evaluate corrosion inhibitors ither
in the laboratory or by attaching to a live pipe. The loop
simulates the flow regime, but the apparatus is relatively
sophisticated, and experiments are expensive and time
consuming.
• The loop is considered sophisticated to be an ideal
laboratory methodology under the scope of this guide.
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18. JET IMPINGEMENT TEST (JIT)
• JIT is a widely used technique to study
flow-induced corrosion.
• JIT is considered to simulate the
turbulence encountered at threaded
joints, bends, valves, welds, and so forth
in tubulars, flow lines, and pipelines
Courtesy picture : https://www.stress.com/flow-corrosion-effects-jet-impingement/ and https://www.corelab.com/sanchez/special-fluid-analysis/jet
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19. OIL-WATER PARTITIONING
• In order to prevent corrosion, the CI must be present in the
aqueous phase.
• This is achieved by partitioning or dispersion of the CI from the
hydrocarbon and is enabled by the CI being water dispersible or,
more commonly, water soluble.
• A determined concentration of CI mixed to the solution of water-
crude oil up to 24 hours.The water phase then separated, then
the efficiency test conducted and compared to condition without
mixing with crude oil.
Courtesy picture : https://purificationikwok.weebly.com/separating-funnel.html
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20. SOLUBILITY
• To check the dispersal of the corrosion inhibitor in the carrier media
• The solubility of CI in carrier fluids (aqueous or liquid hydrocarbons) should be assessed at the prospective
storage temperature, often ambient temperature to -20°C.The main concerns are: loss of solubility of the
active ingredients, with the formation of solids or gunks, and phase separation due to changes in solubility.
• In a 100-mL graduated cylinder, make a solution of the appropriate concentration of the CI in the
recommended carrier (aqueous or hydrocarbon).
• Keep the solution at temperature for at least two weeks. Disqualify the product if a deposit or a separate liquid
phase forms within that period. Report any cloudiness or change in appearance of the liquid. Since the solubility
of inhibitors can vary quite drastically depending on the chemical composition of the water and hydrocarbon
phases, it is recommended that this test be repeated with actual field fluids if at all possible.
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21. EMULSION
• Most of CI contain surfactant to enhance its effectiveness. Surfactant may cause problem
such as create emulsion and foaming.
• The emulsions formed can be quite difficult to remove and can lead to separation
difficulties in the production facilities.
• Shake flask tests are used to evaluate whether the CI will cause the water/hydrocarbon
mixture to form an emulsion.
• Volumes of 100-mL (or other suitable volume) mixtures of oil phase and water phase
are tested.The ratios an be used depending on the system, for example.
• Inject CI at various dosage (from 0 ppm as blank until the 2 or 3 times of field dosage).
Hard shake minimum 100 times.
• Observe the separation, the emulsion layer and time required to separate.
Courtesy picture https://testoil.com/services/oil-analysis/demulsibility/
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22. FOAMING
• The purpose of this test is to evaluate whether CI cause
unacceptable foaming tendencies of field brine/condensate
mixtures in certain temperature and CI concentration.
• The method employs sparging gas through a glass frit into
a solution of chemical in either waters or hydrocarbons.
• The foam height and the stability of the foam are used to
assess the degree of foaming. The effect is compared to a
blank
Courtesy picture https://angusfire.co.uk/services/foam-testing-service/
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23. FILM PERSISTENCY
• Is the capability of a corrosion inhibitor to form a stable and protective film able to
mitigate corrosion without being renewed.A high persistency is mandatory for corrosion
inhibitors to be used in the batch mode; however, persistency is a useful property also for
inhibitors for continuous treatments.2
• Persistency can be assessed in laboratory tests measuring the corrosion rate after
removal of the solution containing the inhibitor and replacing with the same solution free
of corrosion inhibitor; the time the system increases up to the baseline corrosion value is
a measure of the inhibitor persistency.
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24. ENVIRONMENT EVALUATION
Some of parameters in environment evaluation are :
• Toxicity
• Biodegradability
• Bioaccumulation
Environment evaluation shall be conduct especially if the CI will be discharged along
with the treated fluid to the open environment.
Courtesy picture https://en.wikipedia.org/wiki/Environmental_hazardl
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25. TOXICITY
• Toxicity is the degree to which a
chemical substance or a particular
mixture of substances can damage an
organism.
• One method to classify toxicity is by
LC50 test
• LC50 is the concentration of the
chemical in the air or water that will
kill 50% of the test animals with a
single exposure
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26. BIODEGRADABILITY
• Biodegradability is the capacity for biological
degradation of organic materials by living
organisms down to the base substances such as
water, carbon dioxide, methane, basic elements
and biomass.Also known as biological oxygen
demand (BOD)
• Minimum BOD is 60%
Courtesy picture https://textilelearner.blogspot.com/2013/04/determination-of-biological-oxygen.html
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27. BIOACCUMULATION
• Bioaccumulation is the gradual accumulation of substances in an
organism. Bioaccumulation occurs when an organism absorbs a
substance at a rate faster than that at which the substance is lost or
eliminated by catabolism and excretion.
• Bioaccumulation could be calculated as KoW. Kow is defined as the
ratio of a chemical's concentration in the octanol phase to its
concentration in the aqueous phase of a two-phase octanol/water
system.
• Kow = Concentration in octanol phase / Concentration in aqueous
phase
Courtesy picture https://energyeducation.ca/encyclopedia/Biomagnification
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28. REFERENCES
• ASTM G170 Standard Guide for Evaluating and Qualifying Oilfield and Refinery
Corrosion Inhibitors in the Laboratory
• https://shodhganga.inflibnet.ac.in/bitstream/10603/13315/7/07_chapter%203.pdf
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