1、Designation: G 184 06Standard Practice forEvaluating and Qualifying Oil Field and Refinery CorrosionInhibitors Using Rotating Cage1This standard is issued under the fixed designation G 184; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers a generally accepted procedure touse the rotating cage (RC) for evaluating co
3、rrosion inhibitorsfor oil field and refinery applications.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is there
4、sponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2G1 Practice for Preparing, Cleaning, and Evaluating Cor-rosion Test SpecimensG15 Terminol
5、ogy Relating to Corrosion and CorrosionTestingG16 Guide forApplying Statistics toAnalysis of CorrosionDataG31 Practice for Laboratory Immersion Corrosion Testingof MetalsG46 Guide for Examination and Evaluation of PittingCorrosionG 111 Guide for Corrosion Tests in High Temperature orHigh Pressure En
6、vironment, or BothG 170 Guide for Evaluating and Qualifying Oilfield andRefinery Corrosion Inhibitors in the LaboratoryD 1141 Practice for the Preparation of Substitute OceanWaterD 4410 Terminology for Fluvial Sediment3. Terminology3.1 The terminology used throughout shall be in accordancewith Termi
7、nologies G15and D 4410 and Guide G 170.4. Summary of Practice4.1 This practice provides a method of evaluating corrosioninhibitor efficiency in a RC apparatus. The method uses awell-defined rotating specimen setup and mass loss measure-ments to determine corrosion rates in a laboratory apparatus.Mea
8、surements are made at a number of rotation rates toevaluate the inhibitor performance under increasingly severehydrodynamic conditions.5. Significance and Use5.1 Selection of corrosion inhibitor for oil field and refineryapplications involves qualification of corrosion inhibitors in thelaboratory (s
9、ee Guide G 170). Field conditions should besimulated in the laboratory in a fast and cost-effective manner(1).35.2 Oil field corrosion inhibitors should provide protectionover a range of flow conditions from stagnant to that foundduring typical production conditions. Not all inhibitors areequally ef
10、fective over this range of conditions so it is importantfor a proper evaluation of inhibitors to test the inhibitors usinga range of flow conditions.5.3 The RC test system is relatively inexpensive and usessimple flat specimens that allow replicates to be run with eachsetup. (2-13).5.4 In this pract
11、ice, a general procedure is presented toobtain reproducible results using RC to simulate the effects ofdifferent types of coupon materials, inhibitor concentrations,oil, gas and brine compositions, temperature, pressure, andflow. Oil field fluids may often contain sand; however, thispractice does no
12、t cover erosive effects that occur when sand ispresent.1This practice is under the jurisdiction of ASTM Committee G01 on Corrosionof Metals and is the direct responsibility of Subcommittee G01.05 on LaboratoryCorrosion Tests.Current edition approved Jan. 15, 2006. Published February 2006.2For refere
13、nced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to the list of references at
14、the end ofthis standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Apparatus6.1 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,
15、 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
16、 the bottom of the container.At the center of the base, a hole is drilled into which the lowerend of a stirring rod is placed. This arrangement stabilizes thestirrer 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 about34.14
17、 cm2) are supported between two PTFE disks (of 80-mmdiameter) mounted 75 mm apart on the stirring rod (Fig. 2).Holes (10-mm diameter) about 15 mm away from the centerare drilled in the top and bottom PTFE plates of the cage toincrease the turbulence on the inside surface of the coupon(Fig. 3). This
18、experimental setup can be used at temperaturesup to 70C and rotation speeds up to 1000 rpm.6.2 The flow pattern varies, depending on the rotationspeed, the volume of the container, and the fluids. The flowpatterns are described in Guide G 170.FIG. 1 Schematic Diagram of Rotating CageNOTEGaps (typica
19、lly 0.85 6 0.01 cm) between the coupons introducelocalized turbulence.FIG. 2 Photo of Rotating Cage Containing CouponsG1840626.3 Volume of solution to the surface area of the specimenhas some effect on the corrosion rate and hence on the inhibitorefficiencies. The minimum solution volume to metal su
20、rfacearea is not less than 14 cm (11).6.4 Open-beaker tests should not be used because of evapo-ration and contamination. Open-beaker test must not be con-ducted when H2S (hydrogen sulfide) is used. In some tests,provisions might be needed for continuous flow or replenish-ment of the corrosive liqui
21、d, while simultaneously maintaininga controlled atmosphere.6.5 For experiments above atmospheric pressure, a high-temperature, high-pressure rotating cage (HTHPRC) systemand a vessel that can withstand high pressure without leakageshall be used.6.6 The suggested components can be modified, simplifie
22、d,or made more sophisticated to fit the needs of a particularinvestigation.7. Materials7.1 Methods for preparing specimens for tests and forremoving specimens after the test are described in Practice G1.Standard laboratory glassware should be used for weighing andmeasuring reagent volumes.7.2 The co
23、upons shall be made of the material (such ascarbon steel) for which the inhibitor is being evaluated. Thecoupon should have the same metallographic structure as thatused in the service components. The coupons should be groundto a specified surface finish (such as 150-grit). The grindingshould produc
24、e a reproducible surface finish, with no rustdeposits, pits, or deep scratches. All sharp edges on the couponshould be ground. All loose dirt particles should be removed.7.3 The coupons are rinsed with distilled water, degreasedby immersing in acetone (or any suitable alcohol), ultrasoni-cally clean
25、ed for 1 min, and dried. The surface of thespecimens should not be touched with bare hands. The speci-mens are weighed to the nearest 0.1 mg, the dimensions aremeasured to the nearest 0.1 mm, and the surface areas arecalculated.7.4 Freshly prepared specimens are installed in the rotatingcage holder.
26、 If the test is not commenced within 4 h, theprepared coupons shall be stored in a desiccator to avoidpre-rusting.8. Test Solutions8.1 All solutions (oil and aqueous) should be obtained fromthe field for which the inhibitor is being evaluated. These areknown as live solutions. It is important that l
27、ive solutions donot already contain corrosion inhibitor. In the absence of livesolutions, synthetic solutions should be used, the compositionof 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
28、Practice D 1141)should be employed. The solutions should be prepared usinganalytical grade reagents and deionized water.8.2 The solutions should be deoxygenated by passing nitro-gen or any other inert gas for sufficient time to reduce theoxygen content below 5 ppb and preferably below 1 ppb insoluti
29、on. The solution must be kept under deoxygenatedconditions. The oxygen concentration in solution depends onthe quality of gases used to purge the solution. Any leaksthrough the vessel, tubing, and joints shall be avoided.8.3 The appropriate composition of gases is determined bythe composition of gas
30、es in the field for which the inhibitor isevaluated. (WarningHydrogen sulfide (H2S) and carbondioxide (CO2) are corrosive gases.) (WarningH2S is poison-ous and should not be released into the atmosphere.) Theappropriate composition of gas can be obtained by mixing H2Sand CO2streams from the standard
31、 laboratory gas supply.Nitrogen or other inert gases can be used as a diluent to obtainthe required composition of corrosive gases. Alternatively, gasmixtures of the required compositions can be purchased fromsuppliers of industrial gases. The concentrations of impurities,particularly oxygen, shall
32、be kept as low as possible withguidelines of below 5 ppb and preferably under 1 ppb oxygenin solution.8.4 The solution pH before and after testing shall bemeasured, recorded and reported. The solution pH should bemonitored regularly (at least once a day) during the test.8.5 Inhibitor concentrations
33、should be measured and re-ported in % mass/volume or parts per million (ppm). Themethod of injecting the inhibitor into the test solution shouldreflect the actual field application. Water-soluble inhibitorsmay be injected neat (as-received) into the test solution(aqueous phase). To avoid the errors
34、associated with handlingsmall volumes of solution, an inhibitor stock solution may beprepared by diluting the as-received chemical in an appropriatesolvent. The type of solvent and the concentration of the stocksolution depend on the characteristics of the inhibitor and onthe specified test conditio
35、ns.8.6 Oil-soluble, water-dispersible inhibitor solutions areprepared by the following partition method. The requiredamounts of oil and brine are placed in the partitioning vessel(usually a separation funnel). The relative volumes of oil andaqueous phases should reflect the ratios of water and oil i
36、n thefield for which the inhibitor is evaluated. If samples from thefield are not available, heptane, kerosine, or any suitablehydrocarbon may be used. The corrosion inhibitor is added toNOTEHoles (typically 1.0 cm in diameter, and about 1.5 cm from thecenter) introduce localized turbulence.FIG. 3 P
37、hoto of Rotating Cage (Top View)G184063the oil phase. The vessel is vigorously shaken for 1 min to mixboth 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
38、inhibitors (usually as batch inhibitors) aredissolved in the oil phase to form an inhibited oil-phase. Thecoupons are exposed to this solution for a certain amount oftime (usually 30 min). The coupons are then removed andintroduced into the experimental vessel.9. Experimental Procedure for Atmospher
39、ic PressureExperiments9.1 A detailed procedure to determine corrosion rates frommass loss is described in Practice G31.9.2 Solutions are usually prepared in a separate containercalled the preparation vessel, pre-saturated with the requiredgas mixture, and preheated to the required temperature. (Pre-
40、treatment described in Sections 8.4, 8.5, and 8.6 is usuallycarried out in the preparation vessel.) Transfer solutions fromthe preparation vessel to the experimental vessel (described inSection 6) under positive nitrogen or other inert gas pressure tominimize air contamination during the transfer op
41、eration.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, arange of temperature may occur within the vessel. Take care toavoid or minimize the temperature differentials. Heat the test
42、vessels slowly (usually at a rate of 0.1C/s) to avoid overheat-ing. The exact protocol depends on the controller, the size andoutput of the heater, and parameters such as vessel size,amount of liquid, thermal conductivity of liquid, and agitation.Maintain the test temperature within 2C of the specif
43、iedtemperature.9.4 Insert pre-weighed coupons (pretreated as necessary,such as with batch inhibitors), thermometer, and pH probes (asappropriate). Position the liquid inlet and outlet so that none ofthem is protruding into the solution.9.5 Initially all other ports of the experimental vessel,except
44、the inlet and outlet ports are closed. The inlet tubeshould have a Y-joint, where one end is attached to theexperimental vessel. Attach the other two ends to the prepara-tion vessel and to an inert gas, such as argon or nitrogencylinder.9.6 Pass the inert gas to expel oxygen from the experimentalves
45、sel.9.7 After 15 min, stop the gas flow, and close the passagebetween the experimental vessel and the gas cylinder.9.8 Open the passage between the experimental and prepa-ration vessels, and pump the gas-saturated brine, which may ormay not contain inhibitor prepared as per 8.4 or 8.5, into theexper
46、imental vessel.9.9 Close the passage between the experimental and prepa-ration vessels. Maintain the experimental vessel with the heateror the water bath at the required temperature.9.10 The additional gas inlet on top of the vessel shouldallow keeping the gas mixture blanket on top of the solution,
47、which is required when the experiment is planned for a longerduration, for example, more than 24 h. Keep the gas flow rateto a minimum. Take care that the gas does not entrain with thesolution.9.11 Use the speed controller to preset the rotation speedand to start the motor. The rotation speed usuall
48、y stabilizes, asdisplayed by the tachometer, within 30 s. Alternatively therotation speed can be set prior to pumping the solution into thevessel.9.12 Terminate the experiment (typically after 24 h), anddetermine the corrosion rate from the amount of metal loss(after proper cleaning as described in
49、Practice G1)asde-scribed in Practice G31. Examine and evaluate the samples forpitting corrosion as in Guide G46. Calculate the average,standard deviation, and coefficient of variation of the couponscorrosion rate for each run using the method presented inGuide G16. If pitting corrosion is observed, then the generalcorrosion rate determined from mass loss could be invalid.9.13 Determine inhibitor efficiency at each rotation speedand at each inhibitor concentration using the following equa-tion:Inhibitor Efficiency,%5C.RNo.inhibitorC.RInhibitor 3 100C.RNo Inhibitor(1)where:
