ASTM B117-2007a Standard Practice for Operating Salt Spray (Fog) Apparatus.pdf

1、Designation: B 117 07aStandard Practice forOperating Salt Spray (Fog) Apparatus1This standard is issued under the fixed designation B 117; 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 paren

2、theses indicates the year of last reapproval. Asuperscript epsilon (e) 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 the apparatus, procedure, andconditions require

3、d to create and maintain the salt spray (fog)test environment. Suitable apparatus which may be used isdescribed in Appendix X1.1.2 This practice does not prescribe the type of test speci-men or exposure periods to be used for a specific product, northe interpretation to be given to the results.1.3 T

4、he values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4 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-pr

5、iate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B 368 Test Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test)D 609 Practice for Preparation of Cold-Rolled Steel Panelsfor T

6、esting Paint, Varnish, Conversion Coatings, andRelated Coating ProductsD 1193 Specification for Reagent WaterD 1654 Test Method for Evaluation of Painted or CoatedSpecimens Subjected to Corrosive EnvironmentsE70 Test Method for pH of Aqueous Solutions With theGlass ElectrodeE 691 Practice for Conduc

7、ting an Interlaboratory Study toDetermine the Precision of a Test MethodG85 Practice for Modified Salt Spray (Fog) Testing3. Significance and Use3.1 This practice provides a controlled corrosive environ-ment which has been utilized to produce relative corrosionresistance information for specimens of

8、 metals and coatedmetals exposed in a given test chamber.3.2 Prediction of performance in natural environments hasseldom been correlated with salt spray results when used asstand alone data.3.2.1 Correlation and extrapolation of corrosion perfor-mance based on exposure to the test environment provid

9、ed bythis practice are not always predictable.3.2.2 Correlation and extrapolation should be consideredonly in cases where appropriate corroborating long-term atmo-spheric exposures have been conducted.3.3 The reproducibility of results in the salt spray exposureis highly dependent on the type of spe

10、cimens tested and theevaluation criteria selected, as well as the control of theoperating variables. In any testing program, sufficient repli-cates should be included to establish the variability of theresults. Variability has been observed when similar specimensare tested in different fog chambers

11、even though the testingconditions are nominally similar and within the ranges speci-fied in this practice.4. Apparatus4.1 The apparatus required for salt spray (fog) exposureconsists of a fog chamber, a salt solution reservoir, a supply ofsuitably conditioned compressed air, one or more atomizingnoz

12、zles, specimen supports, provision for heating the chamber,and necessary means of control. The size and detailed con-struction of the apparatus are optional, provided the conditionsobtained meet the requirements of this practice.4.2 Drops of solution which accumulate on the ceiling orcover of the ch

13、amber shall not be permitted to fall on thespecimens being exposed.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 Dec. 15, 2007. Published January 2008.

14、 Originallyapproved in 1939. Last previous edition approved in 2007 as B 11707.2For 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 Document Summary page o

15、nthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Copyright by ASTM Intl (all rights reserved); Mon Mar 10 23:04:41 EST 2008Downloaded/printed byGuo Dehua (CNIS) pursuant to License Agreement. No further reproductions

16、 authorized.4.3 Drops of solution which fall from the specimens shallnot be returned to the solution reservoir for respraying.4.4 Material of construction shall be such that it will notaffect the corrosiveness of the fog.4.5 All water used for this practice shall conform to Type IVwater in Specifica

17、tion D 1193 (except that for this practicelimits for chlorides and sodium may be ignored). This does notapply to running tap water. All other water will be referred toas reagent grade.5. Test Specimens5.1 The type and number of test specimens to be used, aswell as the criteria for the evaluation of

18、the test results, shall bedefined in the specifications covering the material or productbeing exposed or shall be mutually agreed upon between thepurchaser and the seller.6. Preparation of Test Specimens6.1 Specimens shall be suitably cleaned. The cleaningmethod shall be optional depending on the na

19、ture of the surfaceand the contaminants. Care shall be taken that specimens arenot recontaminated after cleaning by excessive or carelesshandling.6.2 Specimens for the evaluation of paints and other organiccoatings shall be prepared in accordance with applicablespecification(s) for the material(s) b

20、eing exposed, or as agreedupon between the purchaser and the supplier. Otherwise, thetest specimens shall consist of steel meeting the requirementsof Practice D 609 and shall be cleaned and prepared for coatingin accordance with the applicable procedure of Practice D 609.6.3 Specimens coated with pa

21、ints or nonmetallic coatingsshall not be cleaned or handled excessively prior to test.6.4 Whenever it is desired to determine the development ofcorrosion from an abraded area in the paint or organic coating,a scratch or scribed line shall be made through the coating witha sharp instrument so as to e

22、xpose the underlying metal beforetesting. The conditions of making the scratch shall be asdefined in Test Method D 1654, unless otherwise agreed uponbetween the purchaser and the seller.6.5 Unless otherwise specified, the cut edges of plated,coated, or duplex materials and areas containing identific

23、ationmarks or in contact with the racks or supports shall beprotected with a suitable coating stable under the conditions ofthe practice.NOTE 1Should it be desirable to cut test specimens from parts or frompreplated, painted, or otherwise coated steel sheet, the cut edges shall beprotected by coatin

24、g them with paint, wax, tape, or other effective mediaso that the development of a galvanic effect between such edges and theadjacent plated or otherwise coated metal surfaces, is prevented.7. Position of Specimens During Exposure7.1 The position of the specimens in the salt spray chamberduring the

25、test shall be such that the following conditions aremet:7.1.1 Unless otherwise specified, the specimens shall besupported or suspended between 15 and 30 from the verticaland preferably parallel to the principal direction of flow of fogthrough the chamber, based upon the dominant surface beingtested.

26、7.1.2 The specimens shall not contact each other or anymetallic material or any material capable of acting as a wick.7.1.3 Each specimen shall be placed to permit unencum-bered exposure to the fog.7.1.4 Salt solution from one specimen shall not drip on anyother specimen.NOTE 2Suitable materials for

27、the construction or coating of racks andsupports are glass, rubber, plastic, or suitably coated wood. Bare metalshall not be used. Specimens shall preferably be supported from thebottom or the side. Slotted wooden strips are suitable for the support of flatpanels. Suspension from glass hooks or waxe

28、d string may be used as longas the specified position of the specimens is obtained, if necessary bymeans of secondary support at the bottom of the specimens.8. Salt Solution8.1 The salt solution shall be prepared by dissolving 5 6 1parts by mass of sodium chloride in 95 parts of waterconforming to T

29、ype IV water in Specification D 1193 (exceptthat for this practice limits for chlorides and sodium may beignored). Careful attention should be given to the chemicalcontent of the salt. The salt used shall be sodium chloride withnot more than 0.3 % by mass of total impurities. Halides(Bromide, Fluori

30、de, and Iodide) other than Chloride shallconstitute less than 0.1 % by mass of the salt content. Coppercontent shall be less than 0.3 ppm by mass. Sodium chloridecontaining anti-caking agents shall not be used because suchagents may act as corrosion inhibitors. See Table 1 for a listingof these impu

31、rity restrictions. Upon agreement between thepurchaser and the seller, analysis may be required and limitsTABLE 1 Maximum Allowable Limits for Impurity Levels inSodium ChlorideA,B,CImpurity Description Allowable AmountTotal Impurities # 0.3 %Halides (Bromide, Fluoride and Iodide) excluding Chloride

32、99.9%, then the limits for halides can beignored. This is due to the fact that the halides cannot be $0.1% with a salt purityof 99.9%. If the salt used is of lower purity, then test for halides.B11707a2Copyright by ASTM Intl (all rights reserved); Mon Mar 10 23:04:41 EST 2008Downloaded/printed byGuo

33、 Dehua (CNIS) pursuant to License Agreement. No further reproductions authorized.established for elements or compounds not specified in thechemical composition given above.8.2 The pH of the salt solution shall be such that whenatomized at 35C (95F) the collected solution will be in thepH range from

34、6.5 to 7.2 (Note 3). Before the solution isatomized it shall be free of suspended solids (Note 4). The pHmeasurement shall be made at 25C (77F) using a suitableglass pH-sensing electrode, reference electrode, and pH metersystem in accordance with Test Method E70.NOTE 3Temperature affects the pH of a

35、 salt solution prepared fromwater saturated with carbon dioxide at room temperature and pH adjust-ment may be made by the following three methods:(1) When the pH of a salt solution is adjusted at room temperature, andatomized at 35C (95F), the pH of the collected solution will be higherthan the orig

36、inal solution due to the loss of carbon dioxide at the highertemperature. When the pH of the salt solution is adjusted at roomtemperature, it is therefore necessary to adjust it below 6.5 so the collectedsolution after atomizing at 35C (95F) will meet the pH limits of 6.5 to7.2. Take about a 50-mL s

37、ample of the salt solution as prepared at roomtemperature, boil gently for 30 s, cool, and determine the pH. When thepH of the salt solution is adjusted to 6.5 to 7.2 by this procedure, the pHof the atomized and collected solution at 35C (95F) will come withinthis range.(2) Heating the salt solution

38、 to boiling and cooling to 35C (95F) andmaintaining it at 35C (95F) for approximately 48 h before adjusting thepH produces a solution the pH of which does not materially change whenatomized at 35C (95F).(3) Heating the water from which the salt solution is prepared to 35C(95F) or above, to expel car

39、bon dioxide, and adjusting the pH of the saltsolution within the limits of 6.5 to 7.2 produces a solution the pH of whichdoes not materially change when atomized at 35C (95F).NOTE 4The freshly prepared salt solution may be filtered or decantedbefore it is placed in the reservoir, or the end of the t

40、ube leading from thesolution to the atomizer may be covered with a double layer of cheeseclothto prevent plugging of the nozzle.NOTE 5The pH can be adjusted by additions of dilute ACS reagentgrade hydrochloric acid or sodium hydroxide solutions.9. Air Supply9.1 The compressed air supply to the Air S

41、aturator Towershall be free of grease, oil, and dirt before use by passingthrough well-maintained filters. (Note 6) This air should bemaintained at a sufficient pressure at the base of the AirSaturator Tower to meet the suggested pressures of Table 2 atthe top of the Air Saturator Tower.NOTE 6The ai

42、r supply may be freed from oil and dirt by passing itthrough a suitable oil/water extractor (that is commercially available) tostop any oil from reaching the Air Saturator Tower. Many oil/waterextractors have an expiration indicator, proper preventive maintenanceintervals should take these into acco

43、unt.9.2 The compressed air supply to the atomizer nozzle ornozzles shall be conditioned by introducing it into the bottomof a tower fillwed with water. A common method of introduc-ing the air is through an air dispersion device (X1.4.1). Thelevel of the water must be maintained automatically to ensu

44、readequate humidification. It is common practice to maintain thetemperature in this tower between 46 and 49C (114121F) tooffset the cooling effect of expansion to atmospheric pressureduring the atomization process. Table 2 shows the temperature,at different pressures, that are commonly used to offse

45、t thecooling effect of expansion to atmospheric pressure.9.3 Careful attention should be given to the relationship oftower temperature to pressure since this relationship can havea direct impact to maintaining proper collection rates (Note 7).It is preferable to saturate the air at temperatures well

46、 above thechamber temperature as insurance of a wet fog as listed inTable 2.NOTE 7If the tower is run outside of these suggested temperature andpressure ranges to acheive proper collection rates as described in 10.2 ofthis practice, other means of verifying the proper corrosion rate in thechamber sh

47、ould be investigated, such as the use of control specimens(panels of known performance in the test conducted). It is preferred thatcontrol panels be provided that bracket the expected test specimenperformance. The controls allow for the normalization of test conditionsduring repeated running of the

48、test and will also allow comparisons of testresults from different repeats of the same test. (Refer to Appendix X3,Evaluation of Corrosive Conditions, for mass loss procedures).10. Conditions in the Salt Spray Chamber10.1 TemperatureThe exposure zone of the salt spraychamber shall be maintained at 3

49、5 6 2C (95 6 3F). Each setpoint and its tolerance represents an operational control pointfor equilibrium conditions at a single location in the cabinetwhich may not necessarily represent the uniformity of condi-tions throughout the cabinet. The temperature within theexposure zone of the closed cabinet shall be recorded (Note 8)at least once daily (except on Saturdays, Sundays, and holidayswhen the salt spray test is not interrupted for exposing,rearranging, or removing test specimens or to check andreplenish the solution in the reservoir)NOTE 8A sui