1、Designation: G91 11 (Reapproved 2018)Standard Practice forMonitoring Atmospheric SO2Deposition Rate forAtmospheric Corrosivity Evaluation1This standard is issued under the fixed designation G91; the number immediately following the designation indicates the year of originaladoption or, in the case o
2、f revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers two methods of monitoring atmo-spheric sulfur dioxide, SO2deposition rate
3、s with specificapplication for estimating or evaluating atmospheric corrosiv-ity as it applies to metals commonly used in buildings,structures, vehicles and devices used in outdoor locations.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included i
4、n thisstandard.1.3 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, health, and environmental practices and deter-mine the applicability of regulatory limitatio
5、ns prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization Tech
6、nicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D516 Test Method for Sulfate Ion in WaterD1193 Specification for Reagent WaterD2010/D2010M Test Methods for Evaluation of Total Sul-fation Activity in the Atmosphere by the Lead DioxideTechniqueG16 Guide for Applying S
7、tatistics to Analysis of CorrosionDataG84 Practice for Measurement of Time-of-Wetness on Sur-faces Exposed to Wetting Conditions as in AtmosphericCorrosion TestingG140 Test Method for Determining Atmospheric ChlorideDeposition Rate by Wet Candle MethodG193 Terminology and Acronyms Relating to Corros
8、ion2.2 ISO Standards:3ISO 9225 Corrosion of metals and alloys Corrosivity ofatmospheres Measurement of environmental parametersaffecting corrosivity of atmospheres3. Terminology3.1 DefinitionsThe terminology used herein shall be inaccordance with Terminology and Acronyms G193.4. Summary of Practice4
9、.1 Sulfation plates consisting of a lead peroxide reagent inan inverted dish are exposed for 30-day intervals. The platesare recovered and sulfate analyses performed on the contents todetermine the extent of sulfur capture. Lead peroxide cylindersare also used for monitoring atmospheric SO2in a simi
10、larmanner. The results are reported in terms of milligrams of SO2per square metre per day.5. Significance and Use5.1 Atmospheric corrosion of metallic materials is a func-tion of many weather and atmospheric variables. The effect ofspecific corrodants, such as sulfur dioxide, can accelerate theatmos
11、pheric corrosion of metals significantly. It is important tohave information available for the level of atmospheric SO2when many metals are exposed to the atmosphere in order todetermine their susceptibility to corrosion damage during theirlife time in the atmosphere.5.2 Volumetric analysis of atmos
12、pheric SO2concentrationcarried out on a continuous basis is considered by someinvestigators as the most reliable method of estimating theeffects caused by this gas. However, these methods requiresophisticated monitoring devices together with power suppliesand other equipment that make them unsuitabl
13、e for manyexposure sites. These methods are beyond the scope of thispractice.1This practice is under the jurisdiction of ASTM Committee G01 on Corrosionof Metals and is the direct responsibility of Subcommittee G01.04 on Corrosion ofMetals in Natural Atmospheric and Aqueous Environments.Current edit
14、ion approved May 1, 2018. Published June 2018. Originallyapproved in 1986. Last previous edition approved in 2011 as G91 11. DOI:10.1520/G0091-11R18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStanda
15、rds volume information, refer to the standards Document Summary page onthe ASTM website.3Available from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http:/www.iso.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box
16、C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the
17、 World Trade Organization Technical Barriers to Trade (TBT) Committee.15.3 The sulfation plate method provides a simple techniqueto independently monitor the level of SO2in the atmosphere toyield a weighted average result. The lead peroxide cylinder issimilar technique that produces comparable resul
18、ts, and theresults are more sensitive to low levels of SO2.5.4 Sulfation plate or lead peroxide cylinder results may beused to characterize atmospheric corrosion test sites regardingthe effective average level of SO2in the atmosphere at theselocations.5.5 Either sulfation plate or lead peroxide cyli
19、nder testing isuseful in determining microclimate, seasonal, and long termvariations in the effective average level of SO2.5.6 The results of these sulfur dioxide deposition rate testsmay be used in correlations of atmospheric corrosion rates withatmospheric data to determine the sensitivity of the
20、corrosionrate to SO2level.5.7 The sulfur dioxide monitoring methods may also beused with other methods, such as Practice G84 for measuringtime of wetness and Test Method G140 for atmosphericchloride deposition, to characterize the atmosphere at siteswhere buildings or other construction is planned i
21、n order todetermine the extent of protective measures required formetallic materials.6. Interferences6.1 The lead peroxide reagent used in the sulfation plates orlead peroxide cylinders may convert other sulfur containingcompounds such as mercaptans, hydrogen sulfide, and carbo-nyl sulfide into sulf
22、ate.NOTE 1Hydrogen sulfide and mercaptans, at concentrations 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, ormercaptan
23、s are present in the atmosphere, that is, the odor of rotten eggsis present, the lead peroxide method must not be used to assessatmospheric corrosivity. It should also be noted that no actual measure-ments have been made which would establish the correlation betweenatmospheric H2S, COS, or mercaptan
24、 level and sulfation as measured bythis practice.6.2 The inverted exposure position of the sulfation plate isintended to minimize capture of sulfuric acid aerosols andsulfur bearing species from precipitation. The lead peroxidecylinder method may be more susceptible to capturing sulfuricacid aerosol
25、 particles. However, it should be noted that suchaerosols are rare in most natural environments.7. Preparation of SO2Deposition Monitoring Devices7.1 Sulfation plates can be prepared according to themethod of Huey.4The plate preparation method is given inAppendix X1. Laboratory prepared plates shoul
26、d be exposedwithin 120 days of preparation.7.2 Lead peroxide cylinders can be prepared as shown inISO 9225. The cylinder preparation procedure is also shown inAppendix X2. Lead peroxide cylinders should be exposedwithin 120 days of their preparation, and if stored they shouldbe kept in a cool dry lo
27、cation.8. Exposure of SO2Monitoring Devices8.1 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 order to establish the atmospheric SO2level at anatmospheric co
28、rrosion 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. Thereafter, the location should be monitored with atleast four t
29、ests 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 or urban development, then six tests per year for 3years sh
30、ould again be carried out.8.2 In monitoring exposure sites, a minimum of four platesor two cylinders shall be used for each exposure period.8.2.1 Sites which have a significant grade or elevationvariation should be monitored with at least two plates or onecylinder at the highest elevation and two pl
31、ates or one cylinderat the lowest elevation.8.2.2 Plates and cylinders should be exposed, if possible, atboth the highest and lowest level above the ground at whichcorrosion test specimens are exposed.8.2.3 Sites larger than 10 000 m2shall have at least eightplates or four cylinders exposed for each
32、 period. In rectangularsites on level ground, it is desirable to expose two plates or onecylinder at each corner.NOTE 2Some investigators have reported significantly higher sulfa-tion results at locations closest to the ground.8.3 Installation:8.3.1 Brackets shall be used to hold the sulfation plate
33、ssecurely in an inverted position so that the lead peroxidemixture faces downward. The plate shall be horizontal andshall be placed so that it is not protected from normal windsand air currents. The bracket design should include a retainingclip or other provision to hold the plate in the event of st
34、rongwinds. The retainer clip may be made from stainless steel,spring bronze, hard aluminum alloy (3003H19), or other alloyswith sufficient strength and atmospheric corrosion resistance.Atypical bracket design is shown in Fig. 1.8.3.2 For lead peroxide cylinders, each device shall beexposed in a supp
35、ort similar to that shown in Test MethodG140 for chloride candles. Each cylinder shall be securelymounted in a vertical position with a clamp or other device tohold it securely against wind or other mechanical forces. Acover at least 300 mm in diameter shall be securely mountedabove each cylinder wi
36、th a clearance of 200 mm between thetop on the cylinder and the bottom of the cover. The cover mayalso be rectangular or square with a minimum size of 300 mmfor the smallest dimension. The stand and cover assemblyshould be constructed of materials that are not degraded byatmospheric exposure for the
37、 expected duration of their ser-vice.4Huey, N. A., “The Lead Dioxide Estimation of Sulfur Dioxide Pollution,”Journal of the Air Pollution Control Association, Vol 18, No. 9, 1968, pp. 610611.G91 11 (2018)28.4 A 30 6 2-day exposure period is recommended foreither the plates or cylinders. At the concl
38、usion of this period,the device shall be removed from the bracket or holder andcovered tightly to prevent additional sulfation. Analysis of thespecimens shall be completed within 60 days of the completionof the exposure. The specimen identification, exposurelocation, and exposure initiation date sho
39、uld be recorded whenthe plate exposure is initiated. At the termination of exposure,the completion date should be added to the exposure 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 d
40、evelop a measurable SO2capture on theplate.8.5 The specimen shall be analyzed for sulfate content usingany 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
41、a solution of sodium carbonate. It has been found that 20 mL of50 g L Na2CO3(ACS reagent grade) is sufficient to solubilize the sulfatein this test method in a 3-h period. Thereafter, conventional sulfateanalysis can be employed, for example, by barium precipitation and eithergravimetric or turbidim
42、etric analysis (see Test Method D516).9. Calculation9.1 The sulfate analysis provides the quantity of sulfate oneach specimen analyzed. This should be converted to an SO2capture rate, R, by the following equation:R 5 m 2 m0! 3 MWSO2/MWSO43 A 3 T! (1)where:m = mass of sulfate found in the plate, mg,m
43、0= mass of sulfate found in a blank (unexposed)plate, mg,MWSO2= 64,MWSO4= 96,A = area of the plate, m2, andT = exposure time of the plate, days.R =SO2capture rate, mg SO2/m2day.FIG. 1 Sulfation Plate HolderG91 11 (2018)39.2 The SO2capture rate may be converted to equivalentSO3or SO4values if desired
44、, but for comparison purposes,SO2rates shall be used.9.3 The average value and standard deviation of the valuesshould be calculated according to Guide G16.NOTE 5The maximum sulfur dioxide capture rate for sulfation platesis 9000 mg/m2day, and for cylinders it is 5000 mg/m2day.10. Report10.1 The repo
45、rt shall include the following information:10.1.1 A description of the exposure site and the locationswhere the plates or cylinders were exposed, including thebracket identity number or designation and the location on theexposure stand,10.1.2 The exposure initiation and termination dates ofplates or
46、 cylinders,10.1.3 The identification numbers and sources of the sulfa-tion plates or cylinders if they were obtained from a commer-cial source,10.1.4 The calculated SO2capture rates for each specimenand the average and standard deviations for each site andexposure interval,10.1.5 The sulfate analysi
47、s method, and10.1.6 Any deviations from this practice.10.2 Comparison should be made to previously determinedvalues in ongoing monitoring programs.11. Precision and Bias11.1 Repeatability for a group of plates prepared in onebatch and exposed for 30 days under essentially identicalconditions, the st
48、andard deviation5has been found to be relatedto the average sulfation level by the equation given below:p5 0.079 mp(2)rp5 0.22 mp(3)where:p= standard deviation of the plate SO2capture in mgSO2/m2day,mp= average net SO2capture in mg SO2/m2day,rp= repeatability of SO2capture in mg SO2/m2day.11.1.1 Thi
49、s relationship was determined in 10 runs with 6 ormore plates per run. The standard error of estimate of theregression equation was 0.69 based on 8 degrees of freedom.This error is therefore the lower limit for p, that is, the valueof pbecomes a constant value of 0.69 mg SO2/m2day whenm is less than 8.8 mg SO2/m2day and the repeatability is aconstant 1.93 mg SO2/m2day.11.2 The repeatability of lead peroxide cylinders was esti-mated from results of a study in which forty consecutivemeasurements were taken at two sites in Japan using both thelead peroxide cylinde
