ASTM G184-06(2016)
(Practice)Standard Practice for Evaluating and Qualifying Oil Field and Refinery Corrosion Inhibitors Using Rotating Cage
Standard Practice for Evaluating and Qualifying Oil Field and Refinery Corrosion Inhibitors Using Rotating Cage
SIGNIFICANCE AND USE
5.1 Selection of corrosion inhibitor for oil field and refinery applications involves qualification of corrosion inhibitors in the laboratory (see Guide G170). Field conditions should be simulated in the laboratory in a fast and cost-effective manner (1).4
5.2 Oil field corrosion inhibitors should provide protection over a range of flow conditions from stagnant to that found during typical production conditions. Not all inhibitors are equally effective over this range of conditions so it is important for a proper evaluation of inhibitors to test the inhibitors using a range of flow conditions.
5.3 The RC test system is relatively inexpensive and uses simple flat specimens that allow replicates to be run with each setup. (2-13).
5.4 In this practice, a general procedure is presented to obtain reproducible results using RC to simulate the effects of different types of coupon materials, inhibitor concentrations, oil, gas and brine compositions, temperature, pressure, and flow. Oil field fluids may often contain sand; however, this practice does not cover erosive effects that occur when sand is present.
SCOPE
1.1 This practice covers a generally accepted procedure to use the rotating cage (RC) for evaluating corrosion inhibitors for oil field and refinery applications.
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:G184 −06 (Reapproved 2016)
Standard Practice for
Evaluating and Qualifying Oil Field and Refinery Corrosion
Inhibitors Using Rotating Cage
This standard is issued under the fixed designation G184; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D4410 Terminology for Fluvial Sediment
1.1 This practice covers a generally accepted procedure to
3. Terminology
use the rotating cage (RC) for evaluating corrosion inhibitors
for oil field and refinery applications. 3.1 The terminology used throughout shall be in accordance
with Terminologies G15 and D4410 and Guide G170.
1.2 The values stated in SI units are to be regarded as
standard. The values given in parentheses are for information
4. Summary of Practice
only.
4.1 This practice provides a method of evaluating corrosion
1.3 This standard does not purport to address all of the
inhibitor efficiency in a RC apparatus. The method uses a
safety concerns, if any, associated with its use. It is the
well-defined rotating specimen setup and mass loss measure-
responsibility of the user of this standard to establish appro-
ments to determine corrosion rates in a laboratory apparatus.
priate safety and health practices and determine the applica-
Measurements are made at a number of rotation rates to
bility of regulatory limitations prior to use.
evaluate the inhibitor performance under increasingly severe
hydrodynamic conditions.
2. Referenced Documents
2.1 ASTM Standards:
5. Significance and Use
G1 Practice for Preparing, Cleaning, and Evaluating Corro-
5.1 Selection of corrosion inhibitor for oil field and refinery
sion Test Specimens
applicationsinvolvesqualificationofcorrosioninhibitorsinthe
G15 Terminology Relating to Corrosion and CorrosionTest-
laboratory (see Guide G170). Field conditions should be
ing (Withdrawn 2010)
simulated in the laboratory in a fast and cost-effective manner
G16 Guide for Applying Statistics to Analysis of Corrosion
(1).
Data
G31 Guide for Laboratory Immersion Corrosion Testing of
5.2 Oil field corrosion inhibitors should provide protection
Metals
over a range of flow conditions from stagnant to that found
G46 Guide for Examination and Evaluation of Pitting Cor-
during typical production conditions. Not all inhibitors are
rosion
equallyeffectiveoverthisrangeofconditionssoitisimportant
G111 Guide for Corrosion Tests in High Temperature or
for a proper evaluation of inhibitors to test the inhibitors using
High Pressure Environment, or Both
a range of flow conditions.
G170 Guide for Evaluating and Qualifying Oilfield and
5.3 The RC test system is relatively inexpensive and uses
Refinery Corrosion Inhibitors in the Laboratory
simple flat specimens that allow replicates to be run with each
D1141 Practice for the Preparation of Substitute Ocean
setup. (2-13).
Water
5.4 In this practice, a general procedure is presented to
obtain reproducible results using RC to simulate the effects of
This practice is under the jurisdiction of ASTM Committee G01 on Corrosion
different types of coupon materials, inhibitor concentrations,
of Metals and is the direct responsibility of Subcommittee G01.05 on Laboratory
Corrosion Tests.
oil, gas and brine compositions, temperature, pressure, and
Current edition approved Nov. 1, 2016. Published November 2016. Originally
flow. Oil field fluids may often contain sand; however, this
approved in 2006. Last previous edition approved in 2012 as G184 – 06 (2012).
practice does not cover erosive effects that occur when sand is
DOI: 10.1520/G0184-06R16.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or present.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
The last approved version of this historical standard is referenced on The boldface numbers in parentheses refer to the list of references at the end of
www.astm.org. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G184−06 (2016)
6. Apparatus
6.1 Fig. 1 shows the schematic diagram of the RC system.
An apparatus of suitable size (usually 7500 mL) is used,
consisting of inlet and outlet ports, thermowell, temperature-
regulating device, a heating device (mantle, hot plate, or bath),
and a specimen support system.
6.1.1 The vessel (typically 150-mm diameter) is manufac-
tured from an inert material. Cast acrylic and polytetrafluoro-
ethylene (PTFE) have been used.
6.1.2 A PTFE base is fitted at the bottom of the container.
At the center of the base, a hole is drilled into which the lower
end of a stirring rod is placed. This arrangement stabilizes the
stirrer and the coupons.
6.1.3 Typically, eight coupons (each of 75-mm length,
19-mm width, and 3-mm thickness, and a surface area of about
34.14 cm ) are supported between two PTFE disks (of 80-mm
diameter) mounted 75 mm apart on the stirring rod (Fig. 2).
Holes (10-mm diameter) about 15 mm away from the center
are drilled in the top and bottom PTFE plates of the cage to
increase the turbulence on the inside surface of the coupon
(Fig. 3). This experimental setup can be used at temperatures
up to 70°C and rotation speeds up to 1000 rpm.
NOTE 1—Gaps (typically 0.85 6 0.01 cm) between the coupons
introduce localized turbulence.
6.2 The flow pattern varies, depending on the rotation
FIG. 2Photo of Rotating Cage Containing Coupons
speed, the volume of the container, and the fluids. The flow
patterns are described in Guide G170.
FIG. 1Schematic Diagram of Rotating Cage
G184−06 (2016)
7.4 Freshly prepared specimens are installed in the rotating
cage holder. If the test is not commenced within 4 h, the
prepared coupons shall be stored in a desiccator to avoid
pre-rusting.
8. Test Solutions
8.1 All solutions (oil and aqueous) should be obtained from
the field for which the inhibitor is being evaluated. These are
known as live solutions. It is important that live solutions do
not already contain corrosion inhibitor. In the absence of live
solutions, synthetic solutions should be used, the composition
of which should be based on field water analysis. The compo-
sition of the solution should be determined and reported.
Alternatively, standard brine (such as in Practice D1141)
should be employed. The solutions should be prepared using
NOTE 1—Holes (typically 1.0 cm in diameter, and about 1.5 cm from
analytical grade reagents and deionized water.
the center) introduce localized turbulence.
FIG. 3Photo of Rotating Cage (Top View)
8.2 The solutions should be deoxygenated by passing nitro-
gen or any other inert gas for sufficient time to reduce the
oxygen content below 5 ppb and preferably below 1 ppb in
6.3 Volume of solution to the surface area of the specimen
solution. The solution must be kept under deoxygenated
hassomeeffectonthecorrosionrateandhenceontheinhibitor
conditions. The oxygen concentration in solution depends on
efficiencies. The minimum solution volume to metal surface
the quality of gases used to purge the solution. Any leaks
area is not less than 14 cm (11).
through the vessel, tubing, and joints shall be avoided.
6.4 Open-beaker tests should not be used because of evapo-
8.3 The appropriate composition of gases is determined by
ration and contamination. Open-beaker test must not be con-
the composition of gases in the field for which the inhibitor is
ducted when H S (hydrogen sulfide) is used. In some tests,
evaluated. (Warning—Hydrogen sulfide (H S) and carbon
provisions might be needed for continuous flow or replenish-
dioxide(CO )arecorrosivegases.)(Warning—H Sispoison-
2 2
ment of the corrosive liquid, while simultaneously maintaining
ous and should not be released into the atmosphere.) The
a controlled atmosphere.
appropriate composition of gas can be obtained by mixing H S
6.5 For experiments above atmospheric pressure, a high-
and CO streams from the standard laboratory gas supply.
temperature, high-pressure rotating cage (HTHPRC) system
Nitrogen or other inert gases can be used as a diluent to obtain
and a vessel that can withstand high pressure without leakage
the required composition of corrosive gases.Alternatively, gas
shall be used.
mixtures of the required compositions can be purchased from
suppliers of industrial gases. The concentrations of impurities,
6.6 The suggested components can be modified, simplified,
particularly oxygen, shall be kept as low as possible with
or made more sophisticated to fit the needs of a particular
guidelines of below 5 ppb and preferably under 1 ppb oxygen
investigation.
in solution.
7. Materials
8.4 The solution pH before and after testing shall be
7.1 Methods for preparing specimens for tests and for measured, recorded and reported. The solution pH should be
removing specimens after the test are described in Practice G1. monitored regularly (at least once a day) during the test.
Standardlaboratoryglasswareshouldbeusedforweighingand
8.5 Inhibitor concentrations should be measured and re-
measuring reagent volumes.
ported in % mass/volume or parts per million (ppm). The
7.2 The coupons shall be made of the material (such as method of injecting the inhibitor into the test solution should
carbon steel) for which the inhibitor is being evaluated. The reflect the actual field application. Water-soluble inhibitors
coupon should have the same metallographic structure as that may be injected neat (as-received) into the test solution
usedintheservicecomponents.Thecouponsshouldbeground (aqueous phase). To avoid the errors associated with handling
to a specified surface finish (such as 150-grit). The grinding small volumes of solution, an inhibitor stock solution may be
should produce a reproducible surface finish, with no rust preparedbydilutingtheas-receivedchemicalinanappropriate
deposits, pits, or deep scratches.All sharp edges on the coupon solvent. The type of solvent and the concentration of the stock
should be ground. All loose dirt particles should be removed. solution depend on the characteristics of the inhibitor and on
the specified test conditions.
7.3 The coupons are rinsed with distilled water, degreased
by immersing in acetone (or any suitable alcohol), ultrasoni- 8.6 Oil-soluble, water-dispersible inhibitor solutions are
cally cleaned for 1 min, and dried. The surface of the prepared by the following partition method. The required
specimens should not be touched with bare hands. The speci- amounts of oil and brine are placed in the partitioning vessel
mens are weighed to the nearest 0.1 mg, the dimensions are (usually a separation funnel). The relative volumes of oil and
measured to the nearest 0.1 mm, and the surface areas are aqueous phases should reflect the ratios of water and oil in the
calculated. field for which the inhibitor is evaluated. If samples from the
G184−06 (2016)
field are not available, heptane, kerosine, or any suitable 9.10 The additional gas inlet on top of the vessel should
hydrocarbon may be used. The corrosion inhibitor is added to allow keeping the gas mixture blanket on top of the solution,
the oil phase. The vessel is vigorously shaken for 1 min to mix which is required when the experiment is planned for a longer
bothphasesthoroughly,andthephasesareallowedtoseparate. duration, for example, more than 24 h. Keep the gas flow rate
Heating to the temperature of the field helps in the separation. to a minimum. Take care that the gas does not entrain with the
The aqueous phase is removed and used as test solution. solution.
8.7 Oil-soluble inhibitors (usually as batch inhibitors) are
9.11 Use the speed controller to preset the rotation speed
dissolved in the oil phase to form an inhibited oil-phase. The
and to start the motor. The rotation speed usually stabilizes, as
coupons are exposed to this solution for a certain amount of
displayed by the tachometer, within 30 s. Alternatively the
time (usually 30 min). The coupons are then removed and
rotation speed can be set prior to pumping the solution into the
introduced into the experimental vessel.
vessel.
9. Experimental Procedure for Atmospheric Pressure
9.12 Terminate the experiment (typically after 24 h), and
Experiments
determine the corrosion rate from the amount of metal loss
(afterpropercleaningasdescribedinPracticeG1)asdescribed
9.1 A detailed procedure to determine corrosion rates from
in Practice G31. Examine and evaluate the samples for pitting
mass loss is described in Practice G31.
corrosion as in Guide G46. Calculate the average, standard
9.2 Solutions are usually prepared in a separate container
deviation, and coefficient of variation of the coupons corrosion
called the preparation vessel, pre-saturated with the required
rate for each run using the method presented in Guide G16.If
gas mixture, and preheated to the required temperature. (Pre-
pitting corrosion is observed, then the general corrosion rate
treatment described in Sections 8.4, 8.5, and 8.6 is usually
determined from mass loss could be invalid.
carried out in the preparation vessel.) Transfer solutions from
9.13 Determine inhibitor efficiency at each rotation speed
the preparation vessel to the experimental vessel (described in
and at each inhibitor concentration using the following equa-
Section6)underpositivenitrogenorotherinertgaspressureto
tion:
minimize air contamination during the transfer operation.
C.R 2 C.R
@ # @ #
9.3 Depending on the size of the experimental vessel,
No.inhibitor Inhibitor3100
Inhibitor Efficiency,% 5 (1)
@C.R#
heating unit (mantle, bath, or wrapper around the vessel),
No Inhibitor
difference between room, and experimental temperatures, a
where:
range of temperature may occur within the vessel.Take care to
[C.R] = the corrosion rate in absence of inhibitor,
No.inhibitor
avoid or minimize the temperature differentials. Heat the test
and
vessels slowly (usually at a rate of 0.1°C/s) to avoid overheat-
[C.R] = the corrosion rate in the presence of
inhibitor
ing. The exact protocol depends on the controller, the size and
inhibitor.
output of the heater, and parameters such as vessel size,
amount of liquid, thermal conductivity of liquid, and agitation.
10. Experimental Procedure for High-Temperature,
Maintain the test temperature within 2°C of the specified
High-Pressure Experiments
temperature.
10.1 Ageneralproceduretocarryoutcorrosionexperiments
9.4 Insert pre-weighed coupons (pretreated as n
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: G184 − 06 (Reapproved 2012) G184 − 06 (Reapproved 2016)
Standard Practice for
Evaluating and Qualifying Oil Field and Refinery Corrosion
Inhibitors Using Rotating Cage
This standard is issued under the fixed designation G184; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers a generally accepted procedure to use the rotating cage (RC) for evaluating corrosion inhibitors for oil
field and refinery applications.
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
G1 Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
G15 Terminology Relating to Corrosion and Corrosion Testing (Withdrawn 2010)
G16 Guide for Applying Statistics to Analysis of Corrosion Data
G31 Guide for Laboratory Immersion Corrosion Testing of Metals
G46 Guide for Examination and Evaluation of Pitting Corrosion
G111 Guide for Corrosion Tests in High Temperature or High Pressure Environment, or Both
G170 Guide for Evaluating and Qualifying Oilfield and Refinery Corrosion Inhibitors in the Laboratory
D1141 Practice for the Preparation of Substitute Ocean Water
D4410 Terminology for Fluvial Sediment
3. Terminology
3.1 The terminology used throughout shall be in accordance with Terminologies G15 and D4410 and Guide G170.
4. Summary of Practice
4.1 This practice provides a method of evaluating corrosion inhibitor efficiency in a RC apparatus. The method uses a
well-defined rotating specimen setup and mass loss measurements to determine corrosion rates in a laboratory apparatus.
Measurements are made at a number of rotation rates to evaluate the inhibitor performance under increasingly severe
hydrodynamic conditions.
5. Significance and Use
5.1 Selection of corrosion inhibitor for oil field and refinery applications involves qualification of corrosion inhibitors in the
laboratory (see Guide G170). Field conditions should be simulated in the laboratory in a fast and cost-effective manner (1).
This practice is under the jurisdiction of ASTM Committee G01 on Corrosion of Metals and is the direct responsibility of Subcommittee G01.05 on Laboratory Corrosion
Tests.
Current edition approved Nov. 1, 2012Nov. 1, 2016. Published November 2012November 2016. Originally approved in 2006. Last previous edition approved in 20062012
as G184 – 06. 06 (2012). DOI: 10.1520/G0184-06R12.10.1520/G0184-06R16.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G184 − 06 (2016)
5.2 Oil field corrosion inhibitors should provide protection over a range of flow conditions from stagnant to that found during
typical production conditions. Not all inhibitors are equally effective over this range of conditions so it is important for a proper
evaluation of inhibitors to test the inhibitors using a range of flow conditions.
5.3 The RC test system is relatively inexpensive and uses simple flat specimens that allow replicates to be run with each setup.
(2-13).
5.4 In this practice, a general procedure is presented to obtain reproducible results using RC to simulate the effects of different
types of coupon materials, inhibitor concentrations, oil, gas and brine compositions, temperature, pressure, and flow. Oil field fluids
may often contain sand; however, this practice does not cover erosive effects that occur when sand is present.
6. Apparatus
6.1 Fig. 1 shows the schematic diagram of the RC system. An apparatus of suitable size (usually 7500 mL) is used, consisting
of inlet and outlet ports, thermowell, temperature-regulating device, a heating device (mantle, hot plate, or bath), and a specimen
support system.
6.1.1 The vessel (typically 150-mm diameter) is manufactured from an inert material. Cast acrylic and polytetrafluoroethylene
(PTFE) have been used.
6.1.2 A PTFE base is fitted at the bottom of the container. At the center of the base, a hole is drilled into which the lower end
of a stirring rod is placed. This arrangement stabilizes the stirrer and the coupons.
6.1.3 Typically, eight coupons (each of 75-mm length, 19-mm width, and 3-mm thickness, and a surface area of about 34.14
cm ) are supported between two PTFE disks (of 80-mm diameter) mounted 75 mm apart on the stirring rod (Fig. 2). Holes (10-mm
diameter) about 15 mm away from the center are drilled in the top and bottom PTFE plates of the cage to increase the turbulence
on the inside surface of the coupon (Fig. 3). This experimental setup can be used at temperatures up to 70°C and rotation speeds
up to 1000 rpm.
6.2 The flow pattern varies, depending on the rotation speed, the volume of the container, and the fluids. The flow patterns are
described in Guide G170.
6.3 Volume of solution to the surface area of the specimen has some effect on the corrosion rate and hence on the inhibitor
efficiencies. The minimum solution volume to metal surface area is not less than 14 cm (11).
FIG. 1 Schematic Diagram of Rotating Cage
G184 − 06 (2016)
NOTE 1—Gaps (typically 0.85 6 0.01 cm) between the coupons introduce localized turbulence.
FIG. 2 Photo of Rotating Cage Containing Coupons
NOTE 1—Holes (typically 1.0 cm in diameter, and about 1.5 cm from the center) introduce localized turbulence.
FIG. 3 Photo of Rotating Cage (Top View)
6.4 Open-beaker tests should not be used because of evaporation and contamination. Open-beaker test must not be conducted
when H S (hydrogen sulfide) is used. In some tests, provisions might be needed for continuous flow or replenishment of the
corrosive liquid, while simultaneously maintaining a controlled atmosphere.
6.5 For experiments above atmospheric pressure, a high-temperature, high-pressure rotating cage (HTHPRC) system and a
vessel that can withstand high pressure without leakage shall be used.
6.6 The suggested components can be modified, simplified, or made more sophisticated to fit the needs of a particular
investigation.
7. Materials
7.1 Methods for preparing specimens for tests and for removing specimens after the test are described in Practice G1. Standard
laboratory glassware should be used for weighing and measuring reagent volumes.
7.2 The coupons shall be made of the material (such as carbon steel) for which the inhibitor is being evaluated. The coupon
should have the same metallographic structure as that used in the service components. The coupons should be ground to a specified
surface finish (such as 150-grit). The grinding should produce a reproducible surface finish, with no rust deposits, pits, or deep
scratches. All sharp edges on the coupon should be ground. All loose dirt particles should be removed.
G184 − 06 (2016)
7.3 The coupons are rinsed with distilled water, degreased by immersing in acetone (or any suitable alcohol), ultrasonically
cleaned for 1 min, and dried. The surface of the specimens should not be touched with bare hands. The specimens are weighed
to the nearest 0.1 mg, the dimensions are measured to the nearest 0.1 mm, and the surface areas are calculated.
7.4 Freshly prepared specimens are installed in the rotating cage holder. If the test is not commenced within 4 h, the prepared
coupons shall be stored in a desiccator to avoid pre-rusting.
8. Test Solutions
8.1 All solutions (oil and aqueous) should be obtained from the field for which the inhibitor is being evaluated. These are known
as live solutions. It is important that live solutions do not already contain corrosion inhibitor. In the absence of live solutions,
synthetic solutions should be used, the composition of which should be based on field water analysis. The composition of the
solution should be determined and reported. Alternatively, standard brine (such as in Practice D1141) should be employed. The
solutions should be prepared using analytical grade reagents and deionized water.
8.2 The solutions should be deoxygenated by passing nitrogen or any other inert gas for sufficient time to reduce the oxygen
content below 5 ppb and preferably below 1 ppb in solution. The solution must be kept under deoxygenated conditions. The oxygen
concentration in solution depends on the quality of gases used to purge the solution. Any leaks through the vessel, tubing, and joints
shall be avoided.
8.3 The appropriate composition of gases is determined by the composition of gases in the field for which the inhibitor is
evaluated. (Warning—Hydrogen sulfide (H S) and carbon dioxide (CO ) are corrosive gases.) (Warning—H S is poisonous and
2 2 2
should not be released into the atmosphere.) The appropriate composition of gas can be obtained by mixing H S and CO streams
2 2
from the standard laboratory gas supply. Nitrogen or other inert gases can be used as a diluent to obtain the required composition
of corrosive gases. Alternatively, gas mixtures of the required compositions can be purchased from suppliers of industrial gases.
The concentrations of impurities, particularly oxygen, shall be kept as low as possible with guidelines of below 5 ppb and
preferably under 1 ppb oxygen in solution.
8.4 The solution pH before and after testing shall be measured, recorded and reported. The solution pH should be monitored
regularly (at least once a day) during the test.
8.5 Inhibitor concentrations should be measured and reported in % mass/volume or parts per million (ppm). The method of
injecting the inhibitor into the test solution should reflect the actual field application. Water-soluble inhibitors may be injected neat
(as-received) into the test solution (aqueous phase). To avoid the errors associated with handling small volumes of solution, an
inhibitor stock solution may be prepared by diluting the as-received chemical in an appropriate solvent. The type of solvent and
the concentration of the stock solution depend on the characteristics of the inhibitor and on the specified test conditions.
8.6 Oil-soluble, water-dispersible inhibitor solutions are prepared by the following partition method. The required amounts of
oil and brine are placed in the partitioning vessel (usually a separation funnel). The relative volumes of oil and aqueous phases
should reflect the ratios of water and oil in the field for which the inhibitor is evaluated. If samples from the field are not available,
heptane, kerosine, or any suitable hydrocarbon may be used. The corrosion inhibitor is added to the oil phase. The vessel is
vigorously shaken for 1 min to mix both phases thoroughly, and the phases are allowed to separate. Heating to the temperature
of the field helps in the separation. The aqueous phase is removed and used as test solution.
8.7 Oil-soluble inhibitors (usually as batch inhibitors) are dissolved in the oil phase to form an inhibited oil-phase. The coupons
are exposed to this solution for a certain amount of time (usually 30 min). The coupons are then removed and introduced into the
experimental vessel.
9. Experimental Procedure for Atmospheric Pressure Experiments
9.1 A detailed procedure to determine corrosion rates from mass loss is described in Practice G31.
9.2 Solutions are usually prepared in a separate container called the preparation vessel, pre-saturated with the required gas
mixture, and preheated to the required temperature. (Pretreatment described in Sections 8.4, 8.5, and 8.6 is usually carried out in
the preparation vessel.) Transfer solutions from the preparation vessel to the experimental vessel (described in Section 6) under
positive nitrogen or other inert gas pressure to minimize air contamination during the transfer operation.
9.3 Depending on the size of the experimental vessel, heating unit (mantle, bath, or wrapper around the vessel), difference
between room, and experimental temperatures, a range of temperature may occur within the vessel. Take care to avoid or minimize
the temperature differentials. Heat the test vessels slowly (usually at a rate of 0.1°C/s) to avoid overheating. The exact protocol
depends on the controller, the size and output of the heater, and parameters such as vessel size, amount of liquid, thermal
conductivity of liquid, and agitation. Maintain the test temperature within 2°C of the specified temperature.
9.4 Insert pre-weighed coupons (pretreated as necessary, such as with batch inhibitors), thermometer, and pH probes (as
appropriate). Position the liquid inlet and outlet so that none of them is protruding into the solution.
G184 − 06 (2016)
9.5 Initially all other ports of the experimental vessel, except the inlet and outlet ports are closed. The inlet tube should have
a Y-joint, where one end is attached to the experimental vessel. Attach the other two ends to the preparation vessel and to an inert
gas, such as argon or nitrogen cylinder.
9.6 Pass the inert gas to expel oxygen from the experimental vessel.
9.7 After 15 min, stop the gas flow, and close the passage between the experimental vessel and the gas cylinder.
9.8 Open the passage between the experimental and preparation vessels, and pump the gas-saturated brine, which may or may
not contain inhibitor prepared as per 8.4 or 8.5, into the experimental vessel.
9.9 Close the passage between the experimental and preparation vessels. Maintain the experimental vessel with the heater or
the water bath at the required temperature.
9.10 The additional gas inlet on top of the vessel should allow kee
...
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