ASTM G202-12(2016)

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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: G202 − 12 G202 − 12 (Reapproved 2016)
Standard Test Method for
Using Atmospheric Pressure Rotating Cage
This standard is issued under the fixed designation G202; 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 test method covers a generally accepted procedure to conduct the rotating cage (RC) experiment under atmospheric
pressure.
1.2 The values stated in SI units are to be regarded as the 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:
D1141 Practice for the Preparation of Substitute Ocean Water
D1193 Specification for Reagent Water
D1293 Test Methods for pH of Water
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
G1 Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
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
G170 Guide for Evaluating and Qualifying Oilfield and Refinery Corrosion Inhibitors in the Laboratory
G184 Practice for Evaluating and Qualifying Oil Field and Refinery Corrosion Inhibitors Using Rotating Cage
3. Significance and Use
3.1 The rotating cage (RC) test system is relatively inexpensive and uses simple flat specimens that allow replicates to be run
with each setup. (1-11).
3.2 The RC method can be used to evaluate either corrosion inhibitors, or materials, or both. Guide G184 describes the
procedure to use rotating cage to evaluate corrosion inhibitors.
3.3 In this test method, 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, and flow. Oil field fluids
may often contain sand; however, this test method does not cover erosive effects that occur when sand is present.
4. Apparatus
4.1 Fig. 1 shows the schematic diagram of the RC system. The vessel is manufactured from acrylic. At the bottom of the
container, a PTFE base is snugly fitted. At the center of the base, a hole is drilled, into which the lower end of the rotating shaft
is placed. This arrangement stabilizes the rotating shaft and the coupons. The length of the rotating shaft 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 the top of the cage is 30 cm (11.8
in.) from the bottom cover.
This test method 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 March 2013November 2016. Originally approved in 2009. Last previous edition approved in 20092012
as G202G202 – 12.-09. DOI: 10.1520/G0202-12.10.1520/G0202-12R16.
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 boldface numbers in parentheses refer to a 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
G202 − 12 (2016)
FIG. 1 Schematic Diagram of Rotating Cage
4.2 Eight coupons (each of length 75 mm, width 19 mm, thickness 3 mm, and surface area 34.14 cm )) are supported between
two PTFE disks (of 80-mm diameter) mounted 75 mm apart on the stirring rod (Fig. 2). Holes (diameter 10 mm) 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 rotation speeds up to 1000 rpm.
4.3 Flow patterns inside the RC depend on the rotation speed, the volume of the container, and the nature of the fluids used.
The flow patterns are described in Guide G170.
4.4 Volume of solution to the surface area of the specimen has some effect on the corrosion rate. The minimum solution volume
3 2 3 2
(cm ) to metal surface area (cm ) is not less than 14 cm (cm /cm ) (10).
5. Reagents
5.1 Purity of Reagents—Reagent-grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such
specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity
to permit its use without lessening the accuracy of the determination.
5.2 The composition of the solution shall be determined and reported. Alternatively, standard brine (such as in Practice D1141)
shall be used. The solutions shall be prepared using analytical grade reagents and deionized water (in accordance with Specification
D1193).
5.3 The solutions shall be deoxygenated by passing nitrogen or any other inert gas for sufficient time to reduce the oxygen
content below 5 ppb. The solution shall 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.
5.4 Warning—Hydrogen sulfide (H S) and carbon dioxide (CO ) are corrosive gases. H S is poisonous and shall not be
2 2 2
released to the atmosphere. The appropriate composition of gas can be obtained by mixing H S and CO streams from the standard
2 2
laboratory gas supply. Nitrogen can be used as a diluent to obtain the required composition of corrosive gases. Alternatively, gas
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For Suggestions on the testing of reagents not listed by
the American Chemical Society, see Annual Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
G202 − 12 (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
mixtures of the required compositions can be purchased from suppliers of industrial gases. The concentrations of impurities,
particularly oxygen, shall be kept below 5 ppb.
5.5 The solution pH before and after testing shall be measured, recorded, and reported (in accordance with Test Methods
D1293).
6. Test Specimens
6.1 Methods for preparing specimens for tests and removing specimens after the test are described in Practice G1. Standard
laboratory glassware shall be used for weighing and measuring reagent volumes.
6.2 The coupon shall have the same metallographic structure as that used in the service components. The coupons shall be
ground to a surface finish of 150 grit. The grinding shall produce a reproducible surface finish with no rust deposits, pits, or deep
scratches. All sharp edges on the coupon shall be ground. All loose dirt particles shall be removed.
6.3 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 shall 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.
6.4 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.
7. Procedure
7.1 A detailed procedure to determine corrosion rates from mass loss is described in Practice G31.
7.2 Solutions are prepared and presaturated with the experimental gas mixture. If the solution is prepared in a separate container,
it shall be transferred from the preparation vessel to the experimental vessel under positive nitrogen pressure to minimize air
contamination during the transfer operation.
7.3 The experiment shall be conducted at room temperature (21 to 24°C).
7.4 The pre-weighed coupons and holder (described in 4.2) are inserted into the apparatus.
7.5 The lid of the apparatus is sealed such that oxygen cannot leak into the system through the lid.
7.6 Initially all ports of the experimental vessel (Inlet 1, Inlet 2, and outlet) are closed. A nitrogen gas (or any other inert gas)
cylinder is hooked up to Inlet 2. The outlet is hooked to a gas bubbler or gas trap which allows only one way flow of gas (flowing
out of the apparatus). Both Inlet 2 and the outlet are opened allowing the nit
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