1、Designation: G189 07 (Reapproved 2013)Standard Guide forLaboratory Simulation of Corrosion Under Insulation1This standard is issued under the fixed designation G189; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers the simulation of corrosion underinsulation (CUI), including both general and localized attack,on insulat
3、ed specimens cut from pipe sections exposed to acorrosive environment usually at elevated temperature. Itdescribes a CUI exposure apparatus (hereinafter referred to asa CUI-Cell), preparation of specimens, simulation proceduresfor isothermal or cyclic temperature, or both, and wet/dryconditions, whi
4、ch are parameters that need to be monitoredduring the simulation and the classification of simulation type.1.2 The application of this guide is broad and can incorpo-rate a range of materials, environments and conditions that arebeyond the scope of a single test method. The apparatus andprocedures c
5、ontained herein are principally directed at estab-lishing acceptable procedures for CUI simulation for thepurposes of evaluating the corrosivity of CUI environments oncarbon and low alloy pipe steels, and may possibly beapplicable to other materials as well. However, the same orsimilar procedures ca
6、n also be utilized for the evaluation of (1)CUI on other metals or alloys, (2) anti-corrosive treatments onmetal surfaces, and (3) the potential contribution of thermalinsulation and its constituents on CUI. The only requirementsare that they can be machined, formed or incorporated into theCUI-Cell
7、pipe configuration as described herein.1.3 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.4 This standard does not purport to address
8、all of thesafety concerns, if any, associated with its use. It is theresponsibility 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:2A106/A106M Specifi
9、cation for Seamless Carbon Steel Pipefor High-Temperature ServiceC552 Specification for Cellular Glass Thermal InsulationC871 Test Methods for Chemical Analysis of Thermal Insu-lation Materials for Leachable Chloride, Fluoride, Silicate,and Sodium IonsD1193 Specification for Reagent WaterG1 Practice
10、 for Preparing, Cleaning, and Evaluating Corro-sion Test SpecimensG3 Practice for Conventions Applicable to ElectrochemicalMeasurements in Corrosion TestingG5 Reference Test Method for Making PotentiodynamicAnodic Polarization MeasurementsG15 Terminology Relating to Corrosion and Corrosion Test-ing
11、(Withdrawn 2010)3G31 Guide for Laboratory Immersion Corrosion Testing ofMetalsG46 Guide for Examination and Evaluation of Pitting Cor-rosionG59 Test Method for Conducting Potentiodynamic Polariza-tion Resistance MeasurementsG102 Practice for Calculation of Corrosion Rates and Re-lated Information fr
12、om Electrochemical Measurements3. Terminology3.1 The terminology used herein, if not specifically definedotherwise, shall be construed to be in accordance with Termi-nology G15.1This guide is under the jurisdiction of ASTM Committee G01 on Corrosion ofMetals and is the direct responsibility of Subco
13、mmittee G01.11 on ElectrochemicalMeasurements in Corrosion Testing.Current edition approved Aug. 1, 2013. Published August 2013. Originallyapproved in 2007. Last previous edition approved in 2007 as G189 07. DOI:10.1520/G0189-07R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org
14、, 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 last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor
15、 Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2 Definitions of Terms Specific to This Standard:3.2.1 corrosion under insulation (CUI)the corrosion ofsteel or other materials under thermal insulation due to thepresence of water, oxygen or other corrodants, or combinationsther
16、eof.3.2.2 control conditionan exposure condition using apre-selected environment without the inclusion of inhibitors,protective treatments, or additives to the thermal insulation orexposure environment. It is selected to provide baseline data towhich data from other exposure conditions can be compar
17、ed.3.2.3 protection ratioratio of the corrosion rate with thesurface treatment or particular insulative material, or both, withthat obtained for the control condition.4. Summary of Guide4.1 The CUI-Cell consists of three to six ring specimensseparated by non-conductive spacers and held together by t
18、woblind flanged pipe sections, one on each end. Thermal insula-tion is placed around one-half of the evaluation section of thecell and sealed providing an annular space to retain a corrosiveenvironment. The other half of the insulation is put in place tohave proper heat transfer conditions as a typi
19、cal insulated pipesection with internal heating. Provisions are given herein to usethe specimens as corrosion coupons or electrodes in twoseparate electrochemical cells. One half of the CUI-Cell can beused to perform a CUI simulation under the control conditionwhile the other can be used to evaluate
20、 inhibitors, protectivecoatings or insulative materials.4.2 Corrosion measurements can be made using either massloss data (Procedure A) or electrochemical dynamic polariza-tion resistance methods (Procedure B), or both. This apparatuscan be used to conduct laboratory evaluations under isothermalor c
21、yclic temperature and under wet or wet/dry conditionssimulating desired conditions in service. Comparison of themeasured corrosion rates from exposures conducted withvarious surface treatments on steel and/or with various insula-tive materials with corrosion rates obtained with bare steelunder the c
22、ontrol condition provides the basis for assessment ofprotection efficiency. A value of protection efficiency of lessthan 1.0 indicates reduction in the severity of corrosion relativeto the control condition whereas a value greater than 1.0indicates an increase in the severity of corrosion relative t
23、o thecontrol condition.5. Significance and Use5.1 The corrosion observed on steel and other materialsunder thermal insulation is of great concern for many industriesincluding chemical processing, petroleum refining and electricpower generation. In most cases, insulation is utilized onpiping and vess
24、els to maintain the temperatures of the operat-ing systems for process stabilization and energy conservation.However, these situations can also provide the prerequisites forthe occurrence of general or localized corrosion, or both, and instainless steels, stress corrosion cracking. For example, com-
25、bined with elevated temperatures, CUI can sometimes result inaqueous corrosion rates for steel that are greater than thosefound in conventional immersion tests conducted in either openor closed systems (see Fig. 1).4This figure shows actual CUI4Ashbaugh, W. G., “Corrosion of Metals Under Insulation,
26、” Process IndustriesCorrosion, Ed. B. J. Moniz and W. I. Pollock, ASTM STP 880, West Conshohoken,PA, 1986.NOTE 1The actual CUI corrosion rates can be in excess of the those obtain in conventional laboratory immersion exposures.FIG. 1 Comparison of Actual Plant CUI Corrosion Rates Measurements (Open
27、Data Points Shown is for Plant CUI) with Laboratory Cor-rosion Data Obtained in Open and Closed SystemsG189 07 (2013)2data determined in the field compared with the corrosion datafrom fully immersed corrosion coupons tests.5.2 This guide provides a technical basis for laboratorysimulation of many of
28、 the manifestations of CUI. This is anarea where there has been a need for better simulationtechniques, but until recently, has eluded many investigators.Much of the available experimental data is based on field andin-plant measurements of remaining wall thickness. Laboratorystudies have generally b
29、een limited to simple immersion testsfor the corrosivity of leachants from thermal insulation oncorrosion coupons using techniques similar to those given inPractice G31. The field and inplant tests give an indication ofcorrosion after the fact and can not be easily utilized forexperimental purposes.
30、 The use of coupons in laboratoryimmersion tests can give a general indication of corrosiontendencies. However, in some cases, these procedures areuseful in ranking insulative materials in terms of their tenden-cies to leach corrosive species. However, this immersiontechnique does not always present
31、 an accurate representation ofthe actual CUI tendencies experienced in the service due todifferences in exposure geometry, temperature, cyclictemperatures, or wet/dry conditions in the plant and fieldenvironments.5.3 One of the special aspects of the apparatus and meth-odologies contained herein are
32、 their capabilities to accommo-date several aspects critical to successful simulation of the CUIexposure condition. These are: (1) an idealized annular geom-etry between piping and surrounding thermal insulation, (2)internal heating to produce a hot-wall surface on which CUIcan be quantified, (3) in
33、troduction of ionic solutions into theannular cavity between the piping and thermal insulation, (4)control of the temperature to produce either isothermal orcyclic temperature conditions, and (5) control of the delivery ofthe control or solution to produce wet or wet-dry conditions.Other simpler met
34、hods can be used to run corrosion evalua-tions on specimens immersed in various solutions andleachants from thermal insulation. In some cases, these proce-dures may be acceptable for evaluation of the contribution ofvarious factors on corrosion. However, they do not provideaccommodation of the above
35、 mentioned factors that may beneeded for CUI simulation.5.4 With the CUI-Cell, the pipe material, insulation andenvironment can be selected for the desired simulation needed.Therefore, no single standard exposure condition can bedefined. The guide is designed to assist in the laboratorysimulation of
36、 (1) the influence of different insulation materialson CUI that, in some cases, may contain materials or additives,or both, that can accelerate corrosion, (2) the effect of appliedor otherwise incorporated inhibitors or protective coatings onreducing the extent and severity of CUI. This guide provid
37、esinformation on CUI in a relatively short time (approximately72 h) as well as providing a means of assessing variation ofcorrosion rate with time and environmental conditions.6. Apparatus6.1 The CUI-Cell5can simulate the severity and modality ofcorrosion that has been described to occur under therm
38、alinsulation.4,6Initially this cell was developed for the evaluationof various surface treatments to be applied on the externalsurface of pipe to remediate CUI problems. However,subsequently, this same apparatus has been used successfullyto evaluate the influence of various types of thermal insulati
39、onon CUI. In the cell, corrosion is intended to occur on the outersurface of ring specimens machined from a selected material.Fig. 2 shows a schematic representation of the CUI-Cell. Thecomponents of the cell include the following:6.1.1 Blind Flange SectionsThe CUI-Cell consists of two,nominal two-i
40、nch diameter pipe sections that is, two-inchnominal diameter pipe material with a thickness of 0.187 in.(4.75 mm) as shown in Specification A106/A106M, Grade B,or alternative material to match that being evaluated by thissimulation; one for each end of the cell. Each end includes abolted flange pair
41、 consisting of a weldneck, threaded or lapjoint flange and a blind flange and attached pipe section. Pipeclamps or other suitable devices can be used to hold the flangedends and the ring specimens together.Any device is acceptablethat provides adequate sealing force between the varioussections of th
42、e CUI-Cell.6.1.2 Ring SpecimensThe CUI-Cell consists of six ringspecimens that are separated by nonporous, nonconductivespacers (see Section 7 for more detailed information). Theevaluation portion, which includes alternate ring specimens ofthe intended material and nonconductive rings, is held toget
43、herby two blind flanged pipe sections on both ends. The two setsof three ring specimens and spacers should be separated by anextra thick, nonconductive ring spacer (dam) at the center ofthe CUI-cell. This allows for separate corrosion measurementsto be made on each set of specimens. For electrochemi
44、calmeasurements, each ring specimen should contain an attach-ment screw for connection of electrical leads to the potentiostat(Fig. 2). The connections should be made outside of the areaexposed to the corrosive environment. The nonconductivespacers should be made from a machinable, temperatureresist
45、ant, non-conductive material. Machinable polytetrafluo-roethylene (PTFE) resins with high melting points are suitablein most cases for use up to about 400 to 450F (200 to 230C).5Abayarathna, D., Ashbaugh, W. G., Kane, R. D., McGowan, N., and Heimann,B., “Measurement of Corrosion Under Insulation and
46、 Effectiveness of ProtectiveCoatings,” Corrosion/97, Paper No. 266, NACE International, Houston, Texas,March 1997.6Ullrich, O. A., MTI Technical Report No. 7, “Investigation of an Approach forDetection of Corrosion Under Insulation,” MTI Project 12, Phase II, MaterialsTechnology Institute of the Che
47、mical Process Industries, March 1982.G189 07 (2013)36.1.3 Internal Heater and Temperature ControllerThetemperature on the outer surface of the ring specimens isachieved via an immersion heater (nominally 0.625 in. (1.6cm) in diameter) having 400 W located on the inside of thepipe section mounted thr
48、ough the center of one of the blindflanges using an NPT connection. The temperature of theevaluation section of the CUI-Cell should be monitored andcontrolled with a thermocouple contacting the outer surface ofthe innermost ring specimen at a location outside of the areaexposed to the corrosive envi
49、ronment but under the thermalinsulation as shown in Figs. 3 and 4. The inside of the pipesection is filled with a heat transfer oil stable at the maximumintended temperature. The oil inside the cell assembly isconnected to an oil reservoir of at least 100 mL capacitythrough a metal tube allowing for the expansion and contrac-tion of the oil with temperature. The temperature controlleremployed should be able to control temperature to 62F (1C).If cyclic temperature exposures are desired, the controllershould have multiple programmable temperature settings,heat-up rates
