ASTM A896 A896M-2009(2014) Standard Practice for Conducting Case Studies on Galvanized Structures《镀锌结构传导性研究案例的标准实施规程》.pdf

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1、Designation: A896/A896M 09 (Reapproved 2014)Standard Practice forConducting Case Studies on Galvanized Structures1This standard is issued under the fixed designation A896/A896M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the y

2、ear of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice sets forth the procedures for conductingcase studies of galvanized installations. It is intended

3、forstructural members and other permanent parts of theinstallation, such as railings and other such fabrications.1.2 Included in this practice are recommendations for thevisual inspection of the galvanized structure, measurement ofcoating thickness, and reporting of results.1.3 This specification is

4、 applicable to orders in eitherinch-pound units (as A896) or in SI units (as A896M).Inch-pound units and SI units are not necessarily exactequivalents. Within the text of this specification and whereappropriate, SI units are shown in brackets. Each system shallbe used independently of the other with

5、out combining values inany way.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-priate safety and health practices and determine the applica-bility of regulatory limitatio

6、ns prior to use.2. Referenced Documents2.1 ASTM Standards:2B499 Test Method for Measurement of Coating Thicknessesby the Magnetic Method: Nonmagnetic Coatings onMagnetic Basis MetalsE376 Practice for Measuring Coating Thickness byMagnetic-Field or Eddy-Current (Electromagnetic) Test-ing Methods3. Si

7、gnificance and Use3.1 This practice is applicable to galvanized structuresexposed to the atmosphere or to plant environments, includingbuildings, bridges, and industrial plant constructions.3.2 It provides for the collection of data to document theprotection afforded by the galvanized coating.3.3 Me

8、thod A for conducting a coating thickness surveyaims essentially at an assessment of the general condition ofthe galvanized structure, at the time of the inspection, by takingthickness measurements on several members of the structure.3.4 Method B provides for accurate monitoring of thecoating thickn

9、ess decrease as a function of time, at specificlocations on the structure, in order to assess the corrosivity ofthe environment, the effect of orientation, elevation, or otherfactors.3.5 Method B is not an alternate procedure to MethodA, butis complementary and optional.4. Apparatus4.1 Surface Prepa

10、ration:4.1.1 Water.4.1.2 Cloths, for washing and drying.4.1.3 Soft Fiber Bristle Brush.4.2 Coating Thickness Measurement :4.2.1 Thickness Gage.4.2.2 Steel Calibration Plates and Foils.4.2.3 Permanent Marker.4.2.4 Tape Measure.4.2.5 Center Punch.4.2.6 Hammer.4.3 Electronic Magnetic Flux Gage The use

11、of an elec-tronic magnetic-flux gage in accordance with Method B499 isrecommended. Instruments with an accuracy of 63to65%are commercially available.4.3.1 Probes having a constant pressure feature will mini-mize operator error.4.3.2 The probe assembly should have a probe support ifmeasurements are t

12、o be made on rounded or curved surfaces.4.4 Hand-Held Magnetic GageA hand-held magneticgage using the magnetic attraction principle in accordance withPractice E376 may be used for Method A.5. General Procedure5.1 Background Information:5.1.1 Wherever possible, obtain information on the tonnageand co

13、st of the steel work, the cost of galvanizing, and1This practice is under the jurisdiction of ASTM Committee A05 on Metallic-Coated Iron and Steel Productsand is the direct responsibility of SubcommitteeA05.13 on Structural Shapes and Hardware Specifications.Current edition approved May 1, 2014. Pub

14、lished May 2014. Originallyapproved in 1989. Last previous edition approved in 2009 as A896/A896M - 09.DOI: 10.1520/A0896_A0896M-09R14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume inf

15、ormation, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1estimates of alternative coating costs (initial and maintenance)if the steelwork had been coated by another meth

16、od. Determineif there are areas of the installation which were painted ratherthan galvanized, or painted over galvanizing.5.1.2 Determine if any problems were experienced duringfabrication, galvanizing, construction, and operation.5.2 Corrosive Environment Identification :5.2.1 The galvanized instal

17、lation should be divided accord-ing to the various corrosive environments to which it isexposed. For example, plant atmospheres could be categorizedwith respect to the processing step. Sheltered versus boldlyexposed areas can be considered as two different environments.5.2.2 Pertinent data relating

18、to the corrosive environmentsshould be obtained, such as types of chemical present, concen-tration of fumes, occurrence of spills, temperature fluctuations,amount of rainfall, or the use of de-icing salts.5.3 Visual Inspection:5.3.1 Observe the overall appearance of the galvanizedstructure, and the

19、appearance of each type of plantenvironment, if applicable. Note such characteristics as colorand spangle of the galvanized coating, the presence of rust orstaining, and the condition of other coatings, such as paint.Take note of chemical spills or leaks, the presence of fumes orhigh humidity, and e

20、ffects of orientation, elevation, design, orany other factors causing localized or nonuniform corrosion.5.3.2 The condition of the galvanized coating may varyaccording to section thickness or geometry of the steel. Forexample, there may be differences with respect to light versusheavy sections or ha

21、ndrails versus beams.5.3.3 The use of high silicon steels may be apparent, andshould be noted.5.3.4 Fasteners should be inspected. Look for rust, staining,or mechanical damage.5.4 Coating Thickness Survey:5.4.1 Method A:5.4.1.1 The selection of structural members should be basedmainly on the section

22、 thickness. A minimum of three represen-tative members from each of the two categories of sectionthickness, light (bracing) and heavy (column, beam) should besurveyed for each corrosive environment. Selection of suitablelocations for coating thickness measurements is at the discre-tion of the inspec

23、tor and may be based on factors such asorientation or accessibility. Take measurements in areas wherethe coating is uniform.5.4.1.2 Fasteners should be surveyed where their size per-mits. Measurements should be made on the center of boltheads, or on the flat parts of bolt heads or nuts.5.4.1.3 Calib

24、rate the coating thickness gage against properreference materials before making measurements.5.4.1.4 Clean the surface, using a fine fiber brush or bywashing with water and drying, or both.Avoid removing any ofthe coating material or the film of basic zinc salts.5.4.1.5 At each location, make a mini

25、mum of five measure-ments and determine the mean coating thickness.5.4.2 Method B:5.4.2.1 A minimum of three locations should be surveyedfor each corrosive condition or position of interest. Thelocations need not be on the same steel member. Selection ofsuitable locations is at the discretion of the

26、 inspector. Takemeasurements in areas where the coating is uniform.5.4.2.2 Calibrate the coating thickness gage with properreference materials before the survey is started. Calibrationsshould be checked periodically to ensure continued accuracy ofmeasurements and again at the end of the survey.5.4.2

27、.3 Clean the surface, using a fine fiber bristle brush orby washing with water to remove dirt and dust, or both.(WarningDo not abrade with emery paper or wire brush, orclean in any manner that would tend to remove the zinc coatingor the film of basic zinc salts. By removing the basic zinc saltsfilm,

28、 corrosion can be accelerated.)5.4.2.4 Twenty-five measurements should be made at eachlocation within an area 2 by 2 in. 50 by 50 mm square, andthe mean (X) and the 90 % confidence limit on the mean (Sm90)should be determined (see Appendix X1). A different test areashould be surveyed if Sm90 is grea

29、ter than 0.3 mil 6 m. Ifpossible, use a template with 25 small holes (approximately 0.2in. 4 mm diameter) ina5by5grid, with outside cornermeasurements 2 by 2 in. 50 by 50 mm. Holes should be 0.5in. 12 mm apart horizontally and vertically. The grid shouldbe centered in a larger square measuring 3 by

30、3 in. 75 by 75mm with outside corners containing small holes (see Fig. 1).Put the template on the cleaned surface and mark the 29 holeswith a felt tip marker. Measurements are to be taken startingwith the top left and recorded on the report form in the sameorder as measured on the grid.5.4.2.5 To ma

31、ke test areas easier to locate for future surveys,center punch the outside corners of the 3 by 3 in. 75 by 75mm square so identification marks do not interfere withcoating measurements. If punching is not possible, use paint orother permanent marker (less desirable). If possible, take aphotographic

32、record to properly document the position of eachFIG. 1 Template (not to scale)A896/A896M 09 (2014)2structural member on which measurements were made inrelation to the plant layout.5.4.2.6 Periodic surveys should be conducted. An initialtwo-year interval is recommended for the first several years.Dep

33、ending on the nature of the data collected at the time of thesecond inspection, longer intervals may be considered.5.4.2.7 The same thickness gage, or at least the same type ofinstrument as used in subsequent surveys. The steel calibrationplate should be the same for each survey.5.5 Photographs:5.5.

34、1 Obtain an overall photographic view of theinstallation, from several angles, if possible.5.5.2 Photograph each corrosive environment where mea-surements are made, show the relation of the site to the generalplant layout. If possible, show the fumes or chemicals thatwould normally be present.5.5.3

35、Take close-up photographs where appropriate.5.5.3.1 Include close-up photographs of areas where actualmeasurements were made.5.5.3.2 Take close-up photographs of other areas pertinentto the study, such as those areas showing concentratedcorrosion, coating damage, staining, etc., that is not typical

36、ofthe galvanized structure as a whole.5.5.3.3 Take close-ups of fasteners.5.5.3.4 Take close-ups of painted or other coated areas.6. Report6.1 Report sheets are provided in Appendix X1.6.2 State the name of the company of installation and itslocation. Describe the type of structure if an industrial

37、plant.6.3 The inspector should state his or her name, companycontact, date of the inspection, and type of thickness measuringequipment used.6.4 Present any data that is available regarding tonnage andcost of the steel, and comparison costs of galvanizing versusother coating systems.6.5 Visual Inspec

38、tion:6.5.1 Report the general appearance of the galvanizedstructure or installation, and any noticeable changes since thelast inspection. Report coating characteristics such as color,spangle, stains, rust, and condition of paint coatings, fasteners,and high silicon steels within each type of environ

39、ment, ifapplicable.6.5.2 Relate the photographs to the locations discussed inthe report.6.6 Coating Thickness Measurement :6.6.1 Method AState the range of average coating thick-nesses measured on structural members, including high siliconsteels, and on fasteners. Make mention of differences in coat

40、ingthickness that may arise from such factors as section thickness,orientation, etc.6.6.2 Method BProvide details about each location atwhich thickness measurements were made and state the meanand the 90 % confidence interval, rounding to the least signifi-cant number of digits.6.6.3 Relate photogra

41、phs to the corresponding areas mea-sured.APPENDIXES(Nonmandatory Information)X1. CALCULATION OF 90 % CONFIDENCE INTERVALX1.1 The standard deviation, s, of a series of measurementscan be calculated using the following equation:s 5Xi2 X!2#n 2 1where:Xi= each individual reading,X = mean of group of 25

42、readings, andn = number of measurements.X1.2 The 90 % confidence interval on the mean, Sm90, canbe expressed as follows:Sm90 5ts=nwhere:s = standard deviation, andt = the t distribution value for n 1 degrees of freedom.X1.2.1 Tables containing values for tcan be found in text-books on statistics or

43、in most engineering handbooks. For thenumber of measurements ( n= 25) prescribed in 5.4.2.4,t=1.711 for n-1 degrees of freedom and the value oft =n 5 1.711 5 5 0.34The 90 % confidence interval on the mean for 25 measure-ments can then be written as Sm90 = 0.34s.X1.2.2 If some number other than 25 me

44、asurements is used,the value of tforn-1 degrees of freedom must be determinedfrom statistical tables.X1.2.2.1 Calculation of X, s, andSm90 values can betedious, and the use of an electronic calculator is recom-mended.X1.3 The significance of Sm90 is that there is a 90 %probability that the true valu

45、e of the mean will lie within therangeX6Sm90, the most probable value beingX.Atest programinvolving field measurements has shown that considering aA896/A896M 09 (2014)3corrosion rate of 0.1 mil/year 2.5 m/year, it will be possibleto see a significant difference between average coating thick-nesses r

46、esulting from surveys carried out ten years apart in timeand based on 25 readings.X1.4 Example of Calculations:X1.4.1 Xi= 5.6, 6.5, 6.7, 6.1, 6.6, 5.2, 6.4, 6.0, 7.0, 5.6, 6.2,6.8, 6.0, 5.3, 6.7, 6.1, 6.5, 6.7, 6.5, 5.8, 6.0, 6.4, 6.0, 6.4, 6.3 mil142, 165, 170, 155, 168, 132, 163, 152, 179, 142, 15

47、7, 173,152, 135, 170, 155, 165, 170, 165, 147, 152, 163, 152, 163, 160m.X1.4.2 Mean, X = 6.2 mil 157 m.X1.4.3 Standard deviation, s = 0.5 mil 12 m.X1.4.4 90 % confidence interval, Sm90 = 0.2 mil 4 m.X2. CASE STUDY REPORT SHEETX2.1 Fig. X2.1 shows a case study report sheet.A896/A896M 09 (2014)4FIG. X

48、2.1 Case Study Report SheetA896/A896M 09 (2014)5FIG. X2.1 Case Study Report Sheet (continued)A896/A896M 09 (2014)6FIG. X2.1 Case Study Report Sheet (continued)A896/A896M 09 (2014)7ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item m

49、entionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquart