1、Designation: G 91 97 (Reapproved 2004)Standard Practice forMonitoring Atmospheric SO2Using the Sulfation PlateTechnique1This standard is issued under the fixed designation G 91; 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 a weighted average effective SO2level for a 30-day interval through the use of the sulfat
3、ion platemethod, a technique for estimating the effective SO2content ofthe atmosphere, and especially with regard to the atmosphericcorrosion of stationary structures or panels. This practice isaimed at determining SO2levels rather than sulfuric acidaerosol or acid precipitation.1.2 The results of t
4、his practice correlate approximately withvolumetric SO2concentrations, although the presence of dewor condensed moisture tends to enhance the capture of SO2intothe plate.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility
5、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:2D 516 Test Methods for Sulfate Ion in WaterD 2010/D 2010M Test Method for Evaluation of TotalSulfation
6、 Activity in the Atmosphere by the Lead DioxideTechniqueG 16 Guide for Applying Statistics to Analysis of CorrosionData3. Summary of Practice3.1 Sulfation plates consisting of a lead peroxide reagent inan inverted dish are exposed for 30-day intervals. The platesare recovered and sulfate analyses pe
7、rformed on the contents todetermine the extent of sulfur capture. The results are reportedin terms of milligrams of SO2per square metre per day.4. Significance and Use4.1 Atmospheric corrosion of metallic materials is a func-tion of many weather and atmospheric variables. The effect ofspecific corro
8、dants, such as sulfur dioxide, can accelerate theatmospheric corrosion of metals significantly. The sulfationplate method provides a simple technique to independentlymonitor the level of SO2in the atmosphere to yield a weightedaverage result.4.2 Sulfation plate results may be used to characterizeatm
9、ospheric corrosion test sites regarding the effective averagelevel of SO2in the atmosphere at these locations.4.3 Sulfation plate testing is useful in determining micro-climate, seasonal, and long term variations in the effectiveaverage level of SO2.4.4 The results of sulfation plate tests may be us
10、ed incorrelations of atmospheric corrosion rates with atmosphericdata to determine the sensitivity of the corrosion rate to SO2level.4.5 The sulfation plate method may also be used with othermethods to characterize the atmosphere at sites where build-ings or other construction is planned in order to
11、 determine theextent of protective measures required for metallic materials.5. Interferences5.1 The lead peroxide reagent used in this practice mayconvert other compounds such as mercaptans, hydrogen sul-fide, and carbonyl sulfide into sulfate.NOTE 1Hydrogen sulfide and mercaptans, at concentrations
12、 whichaffect the corrosion of structural metals significantly, are relatively rare inmost atmospheric environments, but their effects regarding the corrosionof metals are not equivalent to sulfur dioxide. Therefore, if H2S, COS, ormercaptans are present in the atmosphere, the lead peroxide method mu
13、stnot be used to assess atmospheric corrosivity. It should also be noted thatno actual measurements have been made which would establish thecorrelation between atmospheric H2S, COS, or mercaptan level andsulfation as measured by this practice.1This practice is under the jurisdiction of ASTM Committe
14、e G01 on Corrosionof Metals and is the direct responsibility of Subcommittee G01.04 on AtmosphericCorrosion.Current edition approved Nov 1, 2004. Published November 2004. Originallyapproved in 1986. Last previous edition approved on 1997 as G 91 97.2For referenced ASTM standards, visit the ASTM webs
15、ite, 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, West Conshohocken, PA 19428-2959, United Stat
16、es.5.2 The inverted exposure position of the sulfation plate isintended to minimize capture of sulfuric acid aerosols andsulfur bearing species from precipitation.6. Sulfation Plate Preparation and Exposure6.1 Sulfation plates can be prepared according to themethod of Huey.3The plate preparation met
17、hod is given inAppendix X1. Laboratory prepared plates should be exposedwithin 120 days of preparation.6.2 In general, the level of atmospheric sulfur dioxide variesseasonally during the year so that a minimal exposure programrequires four 30-day exposures each year at roughly equalintervals. In ord
18、er to establish the atmospheric SO2level at anatmospheric corrosion test site which has not been monitoredpreviously, a program in which six 30-day exposures per yearfor a period of 3 years is recommended. More extensive testingmay be desirable if large variability is encountered in theresults. Ther
19、eafter, the location should be monitored with atleast four tests in a 1-year period every 3 years. If thesubsequent tests are not consistent with the initial testing, thenanother 3-year program of six tests per year is required. Also,if a major change in the general area occurs in terms ofindustrial
20、 or urban development, then six tests per year for 3years should again be carried out.6.3 In monitoring exposure sites, a minimum of four platesshall be used for each exposure period.6.3.1 Sites which have a grade or elevation variation shouldbe monitored with at least two plates at the highest elev
21、ationand two plates at the lowest elevation.6.3.2 Plates should be exposed, if possible, at both thehighest and lowest level above the ground at which corrosiontest specimens are exposed.6.3.3 Sites larger than 10 000 m2shall have at least eightplates exposed for each period. In rectangular sites on
22、 levelground, it is desirable to expose two plates at each corner.NOTE 2Some investigators have reported significantly higher sulfa-tion results at locations closest to the ground.6.4 Brackets shall be used to hold the plates securely in aninverted position so that the lead peroxide mixture facesdow
23、nward. The plate shall be horizontal and shall be placed sothat it is not protected from normal winds and air currents. Thebracket design should include a retaining clip or other provi-sion to hold the plate in the event of strong winds. The retainerclip may be made from stainless steel, spring bron
24、ze, hardaluminum alloy (3003H19), or other alloys with sufficientstrength and atmospheric corrosion resistance. A typicalbracket design is shown in Fig. 1.6.5 A 30 6 2-day exposure period is recommended. At theconclusion of this period, the plates should be removed fromthe bracket and covered tightl
25、y to prevent additional sulfation.Analysis of the plates should be completed within 60 days ofthe completion of the exposure. The plate identification,exposure location, and exposure initiation date should berecorded when the plate exposure is initiated. At the termina-tion of exposure, the completi
26、on date should be added to theexposure records.NOTE 3The 30 day exposure is not very discriminating in areas oflow SO2concentrations. Experience has shown that 60- to 90-dayexposure may be necessary to develop a measurable SO2capture on theplate.6.6 The sulfation plates shall be analyzed for sulfate
27、 contentusing any established quantitative analysis technique.NOTE 4In conducting the sulfate analysis, it is necessary to removethe contents of the sulfation plate and solubilize the sulfate, for example,using a solution of sodium carbonate. It has been found that 20 mL of 50g/L Na2CO3(ACS reagent
28、grade) is sufficient to solubilize the sulfate inthis test method in a 3-hour period. Thereafter, conventional sulfateanalysis can be employed, for example, by barium precipitation and eithergravimetric or turbidimetric analysis (see Test Methods D 516).7. Calculation7.1 The sulfate analysis provide
29、s the quantity of sulfate oneach disc analyzed. This should be converted to an SO2capturerate, R, by the following equation.R 5 m 2 mo! 3 MWSO2/MWSO43 A 3 T (1)where:m = mass of sulfate found in the plate, mg,m0= mass of sulfate found in a blank (unexposed)plate, mg,MWSO2= 64,MWSO4= 96,A = area of t
30、he plate, m2, andT = exposure time of the plate, days.R 5 SO2capture rate, mg SO2/m2day (2)7.2 The SO2capture rate may be converted to equivalentSO3or SO4values if desired, but for comparison purposes,SO2rates shall be used.7.3 The average value and standard deviation of the valuesshould be calculat
31、ed according to Guide G 16.8. Report8.1 The report shall include the following information:8.1.1 A description of the exposure site and the locationswhere the plates were exposed, including the bracket identitynumber or designation and the location on the exposure stand,8.1.2 The exposure initiation
32、 and termination dates,8.1.3 The identification numbers and sources of the sulfa-tion plates,8.1.4 The calculated SO2capture rates for each plate and theaverage and standard deviations for each site and exposureinterval,8.1.5 The sulfate analysis method, and8.1.6 Any deviations from this practice.8.
33、2 Comparison should be made to previously determinedvalues in ongoing monitoring programs.9. Precision and Bias9.1 Repeatability for a group of plates prepared in one batchand exposed for 30 days under essentially identical conditions,3Huey, N. A., “The Lead Dioxide Estimation of Sulfur Dioxide Poll
34、ution,”Journal of the Air Pollution Control Association, Vol 18, No. 9, 1968, pp. 610611.G 91 97 (2004)2the standard deviation4has been found to be related to theaverage sulfation level by the equation given below:s50.0790 m (3)where:s = standard deviation of the plate SO2capture in mgSO2/m2day,m =
35、average net SO2capture in mg SO2/m2day.This relationship was determined in 10 runs with 6 or moreplates per run. The standard error of estimate of the regressionequation was 0.69 based on 8 degrees of freedom. This error istherefore the lower limit for s, that is, the value of s becomesa constant va
36、lue of 0.69 mg SO2/m2day when m is less than8.8 mg SO2/m2day.9.2 ReproducibilityNo statement can be made at this timefor results from plates produced, or analyzed, or both, bydifferent laboratories exposed under identical conditions.9.3 BiasAlthough the dry deposition of SO2from theatmosphere is rel
37、ated to the gaseous SO2concentration in theambient air, (see Fig. 2), the deposition rate is also controlledby other factors such as wind velocity and temperature. Thelead peroxide sulfation plate is considered to be a reliablemeasure of SO2deposition within the limitation discussed inthis section.
38、Consequently, this procedure for measuring atmo-spheric SO2dry depositions is defined only in terms of thispractice.9.4 Other methods of measuring SO2dry deposition includea wet candle technique (Test Method D 2010/D 2010M).10. Keywords10.1 atmospheric corrosion; exposures; measurement; plateprepara
39、tion; sulfate analysis; sulfation plates; sulfur dioxide4Levadie, B., “Sampling and Analysis of Atmospheric Sulfur Dioxide with theLead Dioxide Plate (Huey Plate),” Journal of Testing and Evaluation, Vol 7, No. 2,March 1979, pp. 6167.FIG. 1 Sulfation Plate HolderG 91 97 (2004)3APPENDIX(Nonmandatory
40、Information)X1. SULFATION PLATE PREPARATIONThe following practice may be used to prepare sulfationplates:X1.1 Bond filter paper circles to the bottom of polystyreneculture (petri) dishes. Either a 50-mm to 60-mm dish size isconvenient. The bonding process is carried out by placing afilter paper circle, rough side up (S or through the ASTM website(www.astm.org).G 91 97 (2004)5
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