1、Designation: G 52 00 (Reapproved 2006)Standard Practice forExposing and Evaluating Metals and Alloys in SurfaceSeawater1This standard is issued under the fixed designation G 52; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the y
2、ear of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers conditions for the exposure ofmetals, alloys, and other materials in natural surface seaw
3、atersuch as those typically found in bays, harbors, channels, and soforth,2as contrasted with deep ocean testing.3This practicecovers full immersion, tidal zone and related splash, and sprayzone exposures.2, 41.2 This practice sets forth general procedures that shouldbe followed in conducting seawat
4、er exposure tests so thatmeaningful comparisons may be made from one location toanother.1.3 This practice identifies recommended procedures forevaluating the effects of natural surface seawater on thematerials exposed.1.4 The values stated in SI units are to be regarded as thestandard. The values gi
5、ven in parentheses are for informationonly.1.5 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 and health practices and determine the applica-bility of regulato
6、ry limitations prior to use.2. Referenced Documents2.1 ASTM Standards:5D 3623 Test Method for Testing Antifouling Panels inShallow SubmergenceG1 Practice for Preparing, Cleaning, and Evaluating Cor-rosion Test SpecimensG15 Terminology Relating to Corrosion and CorrosionTestingG30 Practice for Making
7、 and Using U-Bend Stress-Corrosion Test SpecimensG38 Practice for Making and Using C-Ring Stress-Corrosion Test SpecimensG39 Practice for Preparation and Use of Bent-Beam Stress-Corrosion Test SpecimensG46 Guide for Examination and Evaluation of PittingCorrosionG58 Practice for Preparation of Stress
8、-Corrosion TestSpecimens for WeldmentsG78 Guide for Crevice Corrosion Testing of Iron-Base andNickel-Base Stainless Alloys in Seawater and OtherChloride-Containing Aqueous Environments3. Terminology3.1 Terms relative to this subject matter can be found inTerminology G15.4. Significance and Use4.1 Th
9、e procedures described herein are recommended forevaluating the corrosion or marine fouling behavior, or both, ofmaterials exposed to quiescent or local tidal flow conditions, orboth.4.1.1 This practice is not intended to cover the influence ofhigh seawater velocity or the behavior of materials in s
10、eawaterwhich has been transported from its source.4.1.2 Some aspects of this practice may be applicable totesting in tanks and troughs which are continuously providedwith fresh surface seawater. Additionally, some aspects mayalso be applicable to deep ocean testing.NOTE 1Guide G78provides guidance f
11、or conducting crevice corro-sion tests under controlled seawater test conditions.1This practice is under the jurisdiction of ASTM Committee G01 on Corrosionof Metals , and is the direct responsibility of Subcommittee G01.09 on Corrosion inNatural Waters.Current edition approved May 1, 2006. Publishe
12、d May 2006. Originallyapproved in 1976. Last previous edition approved in 2000 as G 5200.2Kirk, W. W. and Pikul, S. J., “Seawater Corrosivity Around the World: Resultsfrom Three Years of Testing,”ASTM STP 1086 Corrosion in Natural Waters, 1990,pp. 3-36.3Reinhart, F. M., “Corrosion of Materials in Hy
13、drospace,” Technical ReportR-304, U.S. Naval Civil Engineering Laboratory, Port Hueneme, CA, December1966.4Phull, B.S., Pikul, S. J., and Kain, R. M., “Seawater Corrosivity Around theWorld: Results from Five Years of Testing,”ASTM STP 1300 Corrosion in NaturalWaters, Vol 2, 1997, pp. 34-73.5For refe
14、renced 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, Wes
15、t Conshohocken, PA 19428-2959, United States.4.2 While the duration of testing may be dictated by the testobjectives, exposures of more than six months or one year arecommonly used to minimize the effects of environmentalvariables associated with seasonal changes or geographiclocation, or both.4.3 T
16、he procedures described are applicable for the expo-sure of simple test panels, welded test panels, or thoseconfigured to assess the effects of crevices, or both, such asthose described in Guide G78. In addition, they are useful fortesting of actual components and fabricated assemblies.4.4 It is pru
17、dent to include control materials with knownresistance to seawater corrosion or fouling, or both, as de-scribed in Test Method D 3623.NOTE 2Materials which have been included in ASTM WorldwideSeawater Corrosivity Studies include UNS K01501 (carbon steel), UNSC70600 (90/10 CuNi) and UNS A95086 (5086-
18、H116 Al).2, 4NOTE 3In the case of evaluations of aluminum alloys, care should beexercised in the location of specimens near copper or high copper-containing alloys. In some instances, it is not sufficient to simplyelectrically isolate specimens to prevent bi-metallic (galvanic) corrosion;copper ions
19、 from nearby corroding copper or copper-base alloys candeposit on aluminum and accelerate its corrosion.5. Test Sites5.1 Test sites should be chosen at locations representative ofnatural seawater environments where the metals or alloys to betested may be used. Ideally, a natural seawater test site s
20、houldhave clean, uncontaminated seawater, be in a protected loca-tion, and have facilities for such tests as splash, tidal, and fullimmersion. Reference should be made to tropical versus otherconditions, and seasonal variations in temperature and indeposition of marine growth on the test panels with
21、 a defined“fouling season.”5.2 Periodic observations of critical water parametersshould be made and reported; depending on the experiment,these might include water temperature, salinity, conductivity,pH, oxygen content, and tidal flow (velocity). If there isconcern about the quality of water at the
22、test site, it issuggested that ammonia, hydrogen sulfide, and carbon dioxidebe determined periodically using analytical chemistry proce-dures.26. Exposure Racks6.1 Test racks should be constructed of a material that willremain intact for the entire proposed period of exposure.Nickel-copper alloy 400
23、 (UNS No. N04400) has been found tobe an excellent material, but is not recommended for holdingaluminum specimens. Coated aluminum racks (6061-T6 or5086-H32) also have given satisfactory service. Nonmetallicracks made from reinforced plastic or treated wood might alsobe used.6.2 Specimens must be in
24、sulated from the test racks.Mounting devices made of porcelain and other non-metallicmaterials are commonly used. It should be recognized that thespecimen contact areas with mounting devices may producecrevice corrosion of some susceptible materials, for example,some stainless steel and aluminum all
25、oys.NOTE 4Bolts used to secure the insulators must be galvanicallycompatible with the test rack.6.3 Spacing of the mounted specimens can be important. Itis desirable to have sufficient space between surfaces of testspecimens to ensure that adequate water flows between themand that with long exposure
26、s the accumulated fouling will notblock off the surface to the presence of the seawater environ-ment.6.4 Specimen location maps or charts should be preparedand maintained to ensure positive identification at the conclu-sion of testing. Pre-exposure photographs of assembled testracks are useful.6.5 R
27、acks may be suspended by such materials as nylon,polyester, or polypropylene rope depending on prevailingconditions. Steel wire rope should be avoided.6.5.1 For multiple year exposures, it is recommended thatthe rack support rope be resistant to degradation by seawater aswell as ultraviolet light.6.
28、6 Exposure racks should be suspended so that attachedspecimens will be oriented vertically and subjected to the fulleffects of the seawater but free of galvanic contact with otherspecimens and with minimal sedimentation of silt and debrison the specimen.6.6.1 It should be recognized that in time som
29、e supportropes may stretch due to the added mass of marine fouling. Inshallow waters, this should be taken into account to avoidunwanted contact with the sea bed or bottom. In some cases,the added mass will also make test rack removal more difficult.NOTE 5It should be recognized that barnacles attac
30、hed to racksupport ropes will create potential hazards if manual lifting is required.6.7 If periodic removals are envisioned, it is recommendedthat different racks be utilized to support specimens for eachtest period. Otherwise, marine fouling and corrosion productson other specimens may be disturbe
31、d and possibly affectsubsequent behavior of the test material.6.7.1 It is prudent to check the security of support ropes andthe presence of the test racks from time-to-time.7. Specimens7.1 When the material to be tested is in sheet form, anominal specimen size of 100 by 300 mm (approximately 4 by12
32、in.) is recommended. Specimens may be larger or smaller tosuit a particular test.7.2 Odd shaped samples and assemblies comprising like ordissimilar metals can also be tested. If testing materials in oddshapes (bolts, nuts, pipes, and so forth) is desired, a means ofsupporting them in the test racks
33、must be devised. It isimportant that the specimens be electrically insulated fromtheir respective supports and from each other to preventformation of galvanic corrosion cells. In some instances it isnot sufficient to isolate specimens electrically to preventcorrosion of one material. For example, gr
34、eat care must beexercised with aluminum specimens or racks so that they willnot be contaminated by copper, which will cause acceleratedcorrosion of the aluminum. A galvanic couple is not necessaryto accelerate the corrosion of aluminum by copper. Copper oralloys containing copper physically located
35、in the vicinity ofaluminum may corrode sufficiently so that accelerated corro-sion of the aluminum may be caused by copper deposition onG 52 00 (2006)2the aluminum. (See Note 3.) Again, appropriate insulatingsupports are required.7.2.1 Some specimen configurations for evaluating resis-tance to crevi
36、ce corrosion or stress corrosion cracking may betested under this practice. Examples are provided in GuideG78, Practices G30, G38, G39, and G58.7.3 The total number of test specimens required should bedetermined from a knowledge of the duration of the test and theplanned removals of the specimens fo
37、r intermediate evalua-tions. For reliable results, a sufficient number of replicatespecimens should be used for removal at each exposure period.Triplicate specimens for each exposure period will usuallysatisfy this requirement. A suitable removal schedule might be0.5, 1, 2, 5, 10, and 20 years. In c
38、ase of uncertainty as to analloys corrosion resistance, shorter intervals might be appro-priate, and corrosion rate data may be used to establish moreappropriate exposure periods.8. Preparation of Specimens8.1 IdentificationSpecimens should be marked in a man-ner that will ensure identification for
39、the life of the test. Oneproven method is to use a series of notches or drilled holesarranged according to some desired code. Numbers stamped onrelatively corrosion-resistant materials may be suitable forsome tests. Another method is to attach a corrosion-resistantmetal tag (for example, alloy 625 (
40、UNS No. N06625), alloyC276 (UNS No. N10276), titanium, or alloy 400 (UNS No.N04400), (except for aluminum alloys), or PTFE) by means ofan insulating cord and a suitably located hole.NOTE 6In long term tests, unless fabricated from antifouling materi-als, identification tags may also become encrusted
41、 with marine fouling.8.2 CleaningOil, grease, and dirt should be removed bydegreasing with a solvent cleaner and scrubbing to removeinsoluble soils. Mill scale should be removed from all testspecimens unless it is specifically desired to perform the testwith the mill scale intact. Pickling with an a
42、ppropriate acid (seePractice G1) grit blasting or machining are acceptable descal-ing methods. If acid pickling is used, care must be taken to stopthe pickling action as soon as the mill scale has been removed.It is recommended that the finish be as close as possible to thecondition in which the mat
43、erial will be used. To facilitateexamination of exposed specimens, it is important that auniform finish be applied to the surface; that is, there should beno pits or other depressions which might look like corrosionattack. To facilitate meaningful examination of exposed speci-mens it is important th
44、at any irregularities on the specimensurfaces be noted initially so that these areas will not beconfused with pits or other corrosion at the completion of theexperiments.8.2.1 When a specific surface finish, such as pickled, scaled,as welded, sandblasted, or ground, is to be evaluated, the finishon
45、the test specimens should be in accordance with testrequirements. Thus, two types of tests are involved here: (1)analloy evaluation test with the surface finish as close as possibleto the condition in which the material will be used, and (2)asurface finish test.8.2.2 To facilitate examination of exp
46、osed specimens, it isimportant that the pre-test surface condition be as defect-free aspossible. Pre-existing pits and other depressions should benoted (or photographed) to avoid possible confusion duringfinal inspection.8.3 WeighingSpecimens should be weighed to the preci-sion preferred by the inve
47、stigator, usually 61 mg. Recordsshould be kept of the mass, physical dimensions, and appear-ance of each specimen, including surfaces and edges, at thebeginning of the test. Changes in the physical appearance andany corrosion losses of the specimen due to exposure can thenbe determined.9. Evaluation
48、 of Test Specimens9.1 Remove specimens from exposure at the scheduledtimes or other appropriate times.9.2 Without scratching the specimens, scrape off marinegrowth and barnacles (see Note 7). Clean the panels inaccordance with Practice G1, and then reweigh to precisionsestablished by the investigato
49、r. For certain tests, it may be ofinterest to preserve corrosion products for laboratory evalua-tion. Photographs before and after cleaning are usually valu-able documentation.NOTE 7Plastic or wooden scrapers should be used to remove bar-nacles.9.3 Determine the mass loss of each specimen from the pre-and post-exposure weighings and convert the results to acorrosion rate (Practice G1) or plot as mass loss per unit areaversus exposure time. Where the corrosion is highly localized(as in pitting or specimens with crevice attack) the calculationof corrosion rates from mass loss
