ASTM G85-2011 Standard Practice for Modified Salt Spray (Fog) Testing《改进的盐喷雾(雾化)试验的标准操作规程》.pdf

1、Designation: G85 11Standard Practice forModified Salt Spray (Fog) Testing1This standard is issued under the fixed designation G85; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision. A number in parentheses i

2、ndicates the year of last reapproval. A superscriptepsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This practice covers and sets forth conditions for fivemodifications in salt

3、spray (fog) testing for specificationpurposes. These are in chronological order of their develop-ment:1.1.1 Annex A1, acetic acid-salt spray test, continuous.1.1.2 Annex A2, cyclic acidified salt spray test.1.1.3 Annex A3, seawater acidified test, cyclic (SWAAT).1.1.4 Annex A4,SO2salt spray test, cy

4、clic.1.1.5 Annex A5, dilute electrolyte cyclic fog dry test.1.2 This practice does not prescribe the type of modifica-tion, test specimen or exposure periods to be used for a specificproduct, nor the interpretation to be given to the results.1.3 The values stated in SI units are to be regarded assta

5、ndard. No other units of measurement are included in thisstandard.1.3.1 ExceptionFahrenheit temperature values are givenfor information only throughout this practice.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of t

6、he user of this standard to consult andestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray (Fog) ApparatusD609 Practice for Preparation of Cold-Roll

7、ed Steel Panelsfor Testing Paint, Varnish, Conversion Coatings, andRelated Coating ProductsD1141 Practice for the Preparation of Substitute OceanWaterD1193 Specification for Reagent WaterD1654 Test Method for Evaluation of Painted or CoatedSpecimens Subjected to Corrosive EnvironmentsE70 Test Method

8、 for pH of Aqueous Solutions With theGlass Electrode3. Significance and Use3.1 This practice is applicable to ferrous and nonferrousmetals; also organic and inorganic coatings. The variationsdescribed herein are useful when a different or more corrosiveenvironment than the salt fog described in Prac

9、tice B117 isdesired.4. Apparatus4.1 Cabinet:4.1.1 The apparatus required for salt spray (fog) testingconsists of a fog chamber, a salt solution reservoir, a supply ofsuitably conditioned compressed air, one or more atomizingnozzles, specimen supports, provision for heating the chamber,and necessary

10、means of control. The size and detailed con-struction of the cabinet are optional, provided the conditionsobtained meet the requirements of this practice. The material ofconstruction shall be such that it will not affect the corrosive-ness of the fog. Suitable apparatus that may be used to obtainthe

11、se conditions is described in Appendix X1 of Practice B117with necessary modifications described in each annex of thispractice.4.1.2 Design the cabinet so that drops of solution thataccumulate on the ceiling or cover of the chamber do not fallon the specimens being tested. Do not return drops of sol

12、utionthat fall from the specimens to the solution reservoir forrespraying.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 May 1, 2011. Published August 2

13、011. Originallyapproved in 1985. Last previous edition approved in 2009 as G8509. DOI:10.1520/G0085-11.2For referenced 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

14、 Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.1.3 Equip the cabinet with one or more timing devices toprovide for intermittent spraying or periodic introduction of agas, or both.4.2 Air S

15、upply:4.2.1 Make sure the compressed air supply to the nozzle ornozzles for atomizing the salt solution is free of oil and dirt andmaintain the air supply between 69 and 172 kPa (10 and 25psi).NOTE 1The air supply may be freed of oil and dirt by passing itthrough a water scrubber or at least 610 mm

16、(2 ft) of suitable cleaningmaterial such as asbestos, sheeps wool, or activated alumina.4.2.2 Temperature in the saturator tower (bubble tower)varies depending on the test method used.4.3 Conditions in Salt-Spray Chamber:4.3.1 TemperatureThe temperature in the exposure zonevaries with the test metho

17、d used. For recommended exposurezone temperatures for the various methods, see the annexes inthis practice. Each set point and its tolerance represents anoperational control point for equilibrium conditions at a singlelocation in the cabinet which may not necessarily represent theuniformity of condi

18、tions throughout the cabinet. Record thetemperature within the exposure zone of the closed cabinet atleast twice a day at least 7 h apart (except on weekends andholidays, when the salt spray test is not interrupted forexposing, rearranging, or removing test specimens or to checkand replenish the sol

19、ution in the reservoir).NOTE 2Suitable methods to record the temperature are a continuousrecording device or a thermometer which can be read from outside theclosed cabinet. Obtain the recorded temperature with the salt spraychamber closed to avoid a false low reading because of wet-bulb effectwhen t

20、he chamber is open.4.3.2 Atomization and Quantity of FogPlace at least twoclean fog collectors within the exposure zone so that no dropsof solution from the test specimens or any other source can becollected. Position the collectors in the proximity of the testspecimens, one nearest to any nozzle an

21、d the other farthestfrom all nozzles. Make sure that for each 80 cm2of horizontal-collecting area fog accumulates in each collector from 1.0 to2.0 mL of solution per hour based on an average run of at least16 h continuous spray.NOTE 3Suitable collecting devices are glass funnels with the stemsinsert

22、ed through stoppers into graduated cylinders or crystallizing dishes.Funnels and dishes with a diameter of 100 mm have an area of about 80cm2.4.3.3 Direct or baffle the nozzle or nozzles so that none ofthe spray can impinge directly on the test specimens.5. Test Specimens5.1 Define the type and numb

23、er of test specimens to be used,as well as the criteria for the evaluation of the test results in thespecifications covering the material or product being tested orupon mutual agreement between the purchaser and the seller.5.2 Preparation of Test Specimens:5.2.1 Clean metallic and metallic-coated sp

24、ecimens. Thecleaning method is optional depending on the nature of thesurface and the contaminants; however, when using a cleaningmethod do not include in the contents abrasives other than apaste of pure magnesium oxide nor of solvents which mayform corrosive or inhibitive films. The use of nitric a

25、cidsolution for the chemical cleaning, or passivation, of stainlesssteel specimens is permissible when agreed upon between thepurchaser and the seller. Take care that specimens are notrecontaminated after cleaning by excessive or careless han-dling.5.2.2 Prepare specimens for evaluation of paints an

26、d otherorganic coatings in accordance with applicable specification(s)for the material(s) being tested, or as agreed upon between thepurchaser and supplier. Otherwise, make sure the test speci-mens consist of steel meeting the requirements of PracticeD609; clean and prepare the specimens for coating

27、 in accor-dance with applicable procedure of Practice D609.5.2.3 Whenever it is desired to determine the developmentof corrosion from an abraded area in the paint or organiccoating, make a scratch or scribed line through the coating witha sharp instrument so that the underlying metal is exposedbefor

28、e testing. Use the conditions of making the scratch asdefined in Test Method D1654, unless otherwise agreed uponbetween the purchaser and seller.5.2.4 Protect the cut edges of plated, coated, or duplexmaterials and areas that contain identification marks or that arein contact with the racks or suppo

29、rts with a suitable coating thatis stable under the conditions of the test, such as ceresin wax,unless otherwise specified.NOTE 4Should it be desirable to cut test specimens from parts or frompreplated, painted, or otherwise coated-steel sheet, protect the cut edgesby coating them with paint, wax, t

30、ape, or other effective media so that thedevelopment of preferential attack or a galvanic effect between such edgesand the adjacent plated or otherwise coated-metal surfaces, is prevented.6. Salt Solutions6.1 Make the salt solutions by using either synthetic sea saltin accordance with Practice D1141

31、 or sodium chloride inaccordance with Practice B117, unless otherwise specified inthe appropriate annex. Make-up water shall be distilled ordeionized water conforming to Type IV water in SpecificationD1193 (except that for this practice, limits for chlorides andsodium may be ignored).6.2 Synthetic S

32、ea Salt Solution (see Annex A3)Make thesalt solution so that it consists of 42 g of synthetic sea salt inaccordance with Practice D1141 per litre of solution (see Note5).6.3 Sodium Chloride Solution (Except AnnexA3 and AnnexA5):Prepare the salt solution by dissolving 5 6 1 parts by weightof sodium c

33、hloride in 95 parts of water conforming to Type IVwater in Specification D1193 (except that for this practice,limits for chlorides and sodium may be ignored) containing notmore than 200 ppm of total solids (see Note 5). Halides(Bromide, Fluoride, and Iodide) other than Chloride shallconstitute less

34、than 0.1 % by mass of the salt content. Coppercontent shall be less than 0.3 ppm by mass. Sodium chloridethat has had anti-caking agents added shall not be used becausesuch agents may act as corrosion inhibitors (see Note 6). SeeTable 1 for a listing of these impurity restrictions. Uponagreement bet

35、ween the purchaser and the seller, analysis maybe required and limits established for elements or compoundsnot specified in the chemical composition given above.G85112NOTE 5The specific gravity of salt solution will change with tem-perature. Table 2 shows salt concentration and density versus temper

36、atureand can be used to determine if the sample measured is within specifica-tion. The sample to be measured may be a composite sample frommultiple fog-collecting devices within a single cabinet, if necessary, toobtain sufficient solution volume for measurement.Table 23shows the salt concentration a

37、nd salt density of 4%, 5%, and6% salt solution between 20 and 40C.Ameasurement that falls within therange between 4 and 6% is acceptable.It is important to understand the equipment being used to measurespecific gravity. One common practice for specific gravity measurement isthe use of a hydrometer.

38、If used, careful attention to the hydrometer typeis important as most are manufactured and calibrated for measurements at15.6C. Since salt density is temperature dependent an offset will benecessary to make an accurate measurement at other temperatures.Contact the hydrometer manufacturer to find the

39、 proper offset for thehydrometer being used.NOTE 6A measurable limit for anti-caking agents is not being definedas a result of how salt is manufactured. During salt manufacturing, it iscommon practice to create salt slurry from the raw salt mined. Acrystallization process then captures the pure salt

40、 from this slurry. Somenaturally occurring anti-caking agents can be formed in this process andare not removed from the resultant product. Avoid salt products whereextra anti-caking agents are added. Additionally, when doing an elementalanalysis of salt there can be trace elements present that eithe

41、r stand aloneor are part of an anti-caking agent. It is not economically feasible to knowwhere such elements came from due to the long list of possible anti-cakingagents that would have to be tested. Therefore a salt product that meets theimpurity, halide, and copper limits with no anti-caking agent

42、s added isacceptable. The salt supplier can provide an analysis of the salt with astatement indicating that anti-caking agents were not added to the product.6.4 The pH of the salt solutions will vary depending on thetest method used. Before the solution is atomized, free it ofsuspended solids (see N

43、ote 7). Take the pH measurementselectrometrically at 25C (77F) using a glass electrode with asaturated potassium chloride bridge in accordance with TestMethod E70.NOTE 7The freshly prepared salt solution may be filtered or decantedbefore it is placed in the reservoir, or the end of the tube leading

44、from thesolution to the atomizer may be covered with a double layer of cheeseclothor suitable nonmetallic filter cloth to prevent plugging of the nozzle.7. Procedure7.1 Position of Specimens During Test:7.1.1 Unless otherwise specified, support or suspend thespecimens between 6 and 45 from the verti

45、cal, and preferablyparallel to the principal direction of horizontal flow of fogthrough the chamber, based upon the dominant surface beingtested. Note that test severity increases as angle from thevertical increases.7.1.2 Do not allow contact of the specimens between eachother, between any metallic

46、material, or between any materialcapable of acting as a wick.7.1.3 Place each specimen so as to permit free settling of fogon all specimens. A minimum spacing between specimens of30 mm is recommended.7.1.4 Do not permit the salt solution from one specimen todrip on any other specimen.7.1.5 It is rec

47、ommended that placement of replicate speci-mens be randomized to avoid possible bias caused by differ-ence in spray patterns. Individual specimens may also berotated daily for the same reason.7.1.6 Suitable materials for the construction or coating ofracks and supports are glass, rubber, plastic, or

48、 suitably coatedwood. Do not use bare metal. Support specimens preferablyfrom the bottom or the side. Slotted wooden, laminated plastic,or inert plastic strips are suitable for the support of flat panels.Suspension from glass hooks or waxed string may be used aslong as the specified position of the

49、specimens is obtained, and,if necessary, by means of secondary support at the bottom ofthe specimens.7.2 Continuity of TestUnless otherwise specified in thespecifications covering the material or product being tested, thetest shall be continuous for the duration of the entire testperiod. Continuous operation implies that the chamber beclosed except for the short daily interruptions necessary toinspect, rearrange, or remove test specimens, to check andreplenish the solution in the reservoir, and to make necessaryrecordings as described in 4.3.1, 4.3.2, and Section 9.