1、Designation: G202 09Standard Test Method forUsing Atmospheric Pressure Rotating Cage1This standard is issued under the fixed designation G202; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in p
2、arentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a generally accepted procedureto conduct the rotating cage (RC) experiment under atmo-spheric pressure.1.2 The values stat
3、ed 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 theresponsibility of the user of this standard to establish appro-priate safety an
4、d health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1141 Practice for the Preparation of Substitute OceanWaterD1193 Specification for Reagent WaterD1293 Test Methods for pH of WaterG1 Practice for Preparing, Cleaning,
5、 and Evaluating Corro-sion Test SpecimensG16 Guide for Applying Statistics to Analysis of CorrosionDataG31 Practice for Laboratory Immersion Corrosion Testingof MetalsG46 Guide for Examination and Evaluation of PittingCorrosionG170 Guide for Evaluating and Qualifying Oilfield andRefinery Corrosion I
6、nhibitors in the LaboratoryG184 Practice for Evaluating and Qualifying Oil Field andRefinery Corrosion Inhibitors Using Rotating Cage3. Significance and Use3.1 The rotating cage (RC) test system is relatively inex-pensive system that uses flat specimens to assess the effect offlow across a specimen
7、on the corrosion that occurs on thespecimen. This system does not produce an easily character-ized flow system but it is adjustable over a wide range of flowrates and uses readily available specimens. (1-11).33.2 The RC method can be used to evaluate either corrosioninhibitors or materials or both.
8、Guide G184 describes theprocedure to use rotating cage to evaluate corrosion inhibitors.3.3 In this test method, a general procedure is presented toobtain reproducible results using atmospheric pressure RCdescribed in Guide G184 to simulate the effects of differenttypes of coupon materials, inhibito
9、r concentrations, oil, gas andsolution compositions, and flow. Oil field fluids may oftencontain sand; however, this test method does not cover erosiveeffects that occur when sand is present.4. Apparatus4.1 Fig. 1 shows the schematic diagram of the atmosphericpressure RC system. The vessel is manufa
10、ctured from acrylic.At the bottom of the container, a polytetrafluoroethylene(PTFE) base is snugly fitted. Vessel made from other materialsmay be used provided it is first ascertained that they arecompatible with the solutions and gases to be used in the test.At the center of the base, a hole is dri
11、lled, into which the lowerend of the rotating shaft is placed. This arrangement stabilizesthe rotating shaft and the coupons. The length of the rotatingshaft between the top and bottom covers is 40 cm (15.7 in.).The rotating cage is attached to the shaft in such a way that thetop of the cage is 30 c
12、m (11.8 in.) from the bottom cover.4.2 Eight identical coupons machined from the same mate-rial (each of length 75 mm, width 19 mm, thickness 3 mm, andsurface area 34.14 cm2) are supported between two PTFE disks(of 80-mm diameter) mounted 75 mm apart on the stirring rod(Fig. 2). Holes (diameter 10 m
13、m) about 15 mm away from thecenter are drilled in the top and bottom PTFE plates of the cageto increase the turbulence on the inside surface of the coupon(Fig. 3). This experimental setup can be used at rotation speedsup to 1000 r/min.4.3 The rotation speed is selected based on field operatingcondit
14、ions. To determine the rotation speed the wall shearstress of the field is first determined. Based on the wall shearstress the rotation speed is calculated. The relationship between1This test method is under the jurisdiction of ASTM Committee G01 onCorrosion of Metals and is the direct responsibilit
15、y of Subcommittee G01.05 onLaboratory Corrosion Tests.Current edition approved Oct. 1, 2009. Published November 2009. DOI:10.1520/G0202-09.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
16、 information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to a list of references at the end ofthis standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.rotation spee
17、d and wall shear stress is described in GuideG170. If the field operating conditions are unknown therotation speed shall be 500 r/min.4.4 Flow patterns inside the RC depend on the rotationspeed, the volume of the container, volume of the solution, andthe nature of the solution used. The flow pattern
18、s are describedin Guide G170.4.5 Volume of solution to the surface area of the specimenhas some effect on the corrosion rate. The minimum solutionvolume (cm3) to metal surface area (cm2) is not less than 14 cm(cm3/cm2) (10).5. Reagents5.1 Purity of ReagentsReagent-grade chemicals shall beused in all
19、 tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.4Other grades may be used,provided it is first ascertained that the reagent is of sufficien
20、tlyhigh purity to permit its use without lessening the accuracy ofthe experiment.5.2 The composition of the solution shall be determined andreported. Alternatively, standard brine (such as in PracticeD1141) shall be used. The solutions shall be prepared using4Reagent Chemicals, American Chemical Soc
21、iety Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacope
22、ial Convention, Inc. (USPC), Rockville,MD.FIG. 1 Schematic Diagram of Rotating CageFIG. 2 Photo of Rotating Cage Containing CouponsGaps(Typically 0.85 6 0.01 cm) between the Coupons IntroduceLocalized TurbulenceG202 092reagents (in accordance with 5.1) and deionized water (inaccordance with Specific
23、ation D1193).5.3 The solution shall be deoxygenated by passing nitrogenor any other inert gas to reduce the oxygen content. Thesolution shall be kept under deoxygenated conditions. Theoxygen concentration in solution depends on the quality ofgases used to purge the solution. The oxygen content ofnit
24、rogen or the inert gas shall be less then 10 ppm by volume.Any leaks through the vessel, tubing, and joints shall beavoided.5.4 WarningHydrogen sulphide (H2S) and carbon diox-ide (CO2) are corrosive gases. H2S is poisonous and shall notbe released to the atmosphere. The appropriate composition ofgas
25、 can be obtained by mixing H2S and CO2streams from thestandard laboratory gas supply. Nitrogen or any other inert gascan be used as a diluent to obtain the required composition ofcorrosive gases. The oxygen content of these gases shall notexceed 10 ppm by volume.5.5 To ensure proper deoxygenation an
26、d presaturation of thesolution at least 1.5 L of purge gas/L of test solution shall bebubbled through the test solution at a rate no less then25 mL/min.NOTE 1Bubbling gas using a tube of internal diameter (0.635 cm or14 in.) at a rate of 4 bubbles/s for 1 h corresponds to passing 1.447 L ofgas, assu
27、ming that the bubbles are spherical in shape with a diameter of14inch (0.635 cm) and a volume of 0.1005 cm3.5.6 The solution pH before and after testing shall bemeasured, recorded, and reported (in accordance with TestMethods D1293).6. Test Specimen6.1 Methods for preparing specimens for tests and r
28、emovingspecimens after the test are described in Practice G1. Standardlaboratory glassware shall be used for weighing and measuringreagent volumes.6.2 The coupon shall have the same metallographic struc-ture as that used in the service components. The coupons shallbe ground to a surface finish of 15
29、0 grit. The grinding shallproduce a reproducible surface finish with no rust deposits,pits, or deep scratches. All sharp edges on the coupon shall beground. All loose dirt particles shall be removed.6.3 The coupons are rinsed with distilled water, degreasedby immersing in acetone (or any suitable al
30、cohol), ultrasoni-cally cleaned for 1 min, and dried. The surface of thespecimens shall 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.6.4 Freshly prepared specimens are installed
31、 in the rotatingcage holder. If the test is not commenced within 4 h, theprepared coupons shall be stored in a desiccator to avoidpre-rusting.7. Procedure7.1 A detailed procedure to determine corrosion rates frommass loss is described in Practice G31.7.2 The solution is prepared, deoxygenated and pr
32、esaturatedwith appropriate gas or gas mixture in a separate container. ItFIG. 3 Photo of Rotating Cage (Top View)Holes (Typically 1.0 cm Diameter, about 1.5 cm from the Center) Introduce LocalizedTurbulenceG202 093shall be transferred to the experimental vessel under positivenitrogen pressure to min
33、imize air contamination during thetransfer operation.7.3 The experiment shall be conducted at room temperature(21 to 24C).7.4 The pre-weighed coupons and holder (described in 4.2)are inserted into the experimental vessel, before transferringthe solution into the experimental vessel.7.5 The lid of th
34、e experimental vessel is sealed such thatoxygen cannot leak into the system through the lid.7.6 Initially all ports of the experimental vessel (Inlet 1,Inlet 2 and the outlet) are closed. A nitrogen gas (or any otherinert gas) cylinder is hooked up to Inlet 2. The outlet is hookedto a gas bubbler or
35、 gas trap which allows only one way flow ofgas (flowing out of the apparatus). Both Inlet 2 and the outletare opened allowing the nitrogen gas to pass through theapparatus. The apparatus shall be deoxygenated by passingnitrogen or any other inert gas at a rate of 4 bubbles/s for aminimum of 1 h/L of
36、 internal volume (see Note 1). The oxygencontent of the nitrogen or inert gas shall be less than 10 ppm byvolume.7.7 Inlet 1 is hooked up to the container of the preparedsolution. Inlet 2 is closed and Inlet 1 is opened. The solution ispumped into the apparatus without allowing the entry ofoxygen. I
37、nlet 1 is closed. This time is considered as the start ofthe experiment.7.8 The experimental gas mixture is hooked up to Inlet 2.Inlet 2 is opened allowing the experimental gas mixture toenter the apparatus. A continuous flow of gas shall be main-tained through the apparatus (entering Inlet 2 and ex
38、iting theoutlet) throughout the experiment in order to avoid oxygencontamination. Precautions shall be taken so that the gas doesnot entrain with the solution.7.9 The speed controller is used to set the rotation speed andstart the motor. The actions described in 7.8 and 7.9 shall becompleted within
39、5 min of completing the action described in7.7.7.10 The experiment is terminated (after a minimum of 24h) by draining the solution through Inlet 1. After the solution isdrained the experimental vessel is purged with nitrogen or inertgas before retrieving the samples to avoid exposure of operatorto a
40、cid gases if used. The corrosion rate is determined from theamount of mass loss in accordance with Practices G1 and G31.Experiments shall be run in duplicate. If the difference betweenthe duplicate runs exceeds 10% for the corrosion rates thenanother set of duplicate runs shall be performed and thea
41、verage of all four runs shall be reported. The samples areexamined and evaluated for pitting corrosion in accordancewith Guide G46. The average, standard deviation, and coeffi-cient of variation of the coupons corrosion rate for each runshall be calculated using the method presented in Guide G16.If
42、pitting corrosion is observed, then the general corrosion ratedetermined from mass loss could be invalid.8. Report8.1 All information and data shall be recorded as com-pletely as possible. Practice G31 provides a checklist forreporting corrosion data.8.2 Rotation speed and the rational of using the
43、rotatingspeed shall be recorded.8.3 Average corrosion rates (in mm/y and mpy) calculatedfrom mass loss from all eight coupons used in the test and thestandard deviation at each rotation rate shall be reported.8.4 The following checklist is a recommended guide forreporting important information:8.4.1
44、 Solution chemistry, pH, and concentration (anychanges during test);8.4.2 Volume of test solution;8.4.3 Volume of the experimental vessel;8.4.4 Duration of the test;8.4.5 Chemical composition or tradename of metal;8.4.6 Composition of gas mixture8.4.7 Number, form, and metallurgical conditions of sp
45、eci-men;8.4.8 Exact size, shape, and area of each specimen;8.4.9 Method used to clean specimens after experiment andthe extent of any error expected by this treatment;8.4.10 Initial and final masses and actual mass losses; and8.4.11 Evaluation of attack if other than general, such as pitdepth and di
46、stribution, standard deviation and coefficient ofvariation, crevice corrosion, and results of microscopicalexamination.9. Precision and Bias9.1 PrecisionThe precision of the standard test methodfor using the atmospheric pressure rotating cage method isbeing determined by means of an interlaboratory
47、test program.Preliminary tests at a single laboratory have been made toexamine the issue of test repeatability. In these tests type AISI1018 carbon steel specimens were run in a substitute for oceanwater made up according to Practice D1141 at room tempera-ture (21 to 24C) with the solution deaerated
48、 by sparging withultra pure nitrogen for 24 h prior to running the test. Thesolution was under CO2blanket during the experiment. Thesteel specimens were polished with 400 grit abrasive initially.Two operators were chosen to run five replicate tests at each ofthe following rotation speeds: 200, 500,
49、and 800 r/min for a24 h exposure. The corrosion rate averages, standard devia-tions and coefficients of variation for each run were calculated,and the repeatability statistics for these runs are shown belowin Table 1 and Table 2. Repeatability values are calculated as2.8 times the repeatability standard deviations.NOTE 2It should be noted that Operator 1 had no previous experiencewith this test, and Operator 2 had several years of experience. The resultsfor repeatability standard deviation, sr, are significantly different betweenthese operators, with Operator 2 showing a
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