1、Designation: G 101 04Standard Guide forEstimating the Atmospheric Corrosion Resistance of Low-Alloy Steels1This standard is issued under the fixed designation G 101; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide presents two methods for estimating theatmospheric corrosion resistance of low-alloy weatheringsteels, such as
3、those described in Specifications A 242/A 242M,A 588/A 588M,A 606 Type 4,A 709/A 709M grades50W, HPS 70W, and 100W, A 852/A 852M, and A 871/A 871M. One method gives an estimate of the long-termthickness loss of a steel at a specific site based on results ofshort-term tests. The other gives an estima
4、te of relativecorrosion resistance based on chemical composition.2. Referenced Documents2.1 ASTM Standards:2A 242/A 242M Specification for High-Strength Low-AlloyStructural SteelA 588/A 588M Specification for High-Strength Low-AlloyStructural Steel with 50 Ksi (345 MPa) Minimum YieldPoint to 4 in. (
5、100 mm) ThickA 606 Specification for Steel, Sheet and Strip, HighStrength, Low-Alloy, Hot-Rolled and Cold Rolled, WithImproved Atmospheric Corrosion ResistanceA 709/A 709M Specification for Carbon and High-StrengthLow-Alloy Structural Steel Shapes, Plates, and Bars andQuenched-and-Tempered Alloy Str
6、uctural Steel Plates forBridgesA 852/A 852M Specification for Quenched and TemperedLow-Alloy Structural Steel Plate with 70 ksi (485 MPa)Minimum Yield Strength to 4 in (100 mm) ThickA 871/A 871M Specification for High Strength Low-AlloyStructural Steel Plate With Atmospheric Corrosion Resis-tanceG1
7、Practice for Preparing, Cleaning, and Evaluating Cor-rosion Test SpecimensG16 Guide forApplying Statistics toAnalysis of CorrosionDataG50 Practice for Conducting Atmospheric Corrosion Testson Metals3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 low-alloy steelsIron-carbon all
8、oys containinggreater than 1.0 % but less than 5.0 %, by mass, total alloyingelements.NOTE 1Most “low-alloy weathering steels” contain additions of bothchromium and copper, and may also contain additions of silicon, nickel,phosphorus, or other alloying elements which enhance atmosphericcorrosion res
9、istance.4. Summary of Guide4.1 In this guide, two general methods are presented forestimating the atmospheric corrosion resistance of low-alloyweathering steels. These are not alternative methods; eachmethod is intended for a specific purpose, as outlined in 5.2 and5.3.4.1.1 The first method utilize
10、s linear regression analysis ofshort-term atmospheric corrosion data to enable prediction oflong-term performance by an extrapolation method.4.1.2 The second method utilizes predictive equations basedon the steel composition to calculate indices of atmosphericcorrosion resistance.5. Significance and
11、 Use5.1 In the past, ASTM specifications for low-alloy weath-ering steels, such as Specifications A 242/A 242M, A 588/A 588M,A 606 Type 4,A 709/A 709M Grade 50W, HPS 70W,and 100W, A 852/A 852M, and A 871/A 871M stated that theatmospheric corrosion resistance of these steels is “approxi-mately two ti
12、mes that of carbon structural steel with copper.”Afootnote in the specifications stated that “two times carbonstructural steel with copper is equivalent to four times carbonstructural steel without copper (Cu 0.02 maximum).” Because1This guide is under the jurisdiction of ASTM Committee G01 on Corro
13、sion ofMetals and is the direct responsibility of Subcommittee G01.04 on AtmosphericCorrosion.Current edition approved May 1, 2004. Published June 2004. Originallyapproved in 1989. Last previous edition approved in 2001 as G 101 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org
14、, 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 States.such statement
15、s relating the corrosion resistance of weatheringsteels to that of other steels are imprecise and, more impor-tantly, lack significance to the user (1 and 2)3, the presentguide was prepared to describe more meaningful methods ofestimating the atmospheric corrosion resistance of weatheringsteels.5.2
16、The first method of this guide is intended for use inestimating the expected long-term atmospheric corrosionlosses of specific grades of low-alloy steels in various envi-ronments, utilizing existing short-term atmospheric corrosiondata for these grades of steel.5.3 The second method of this guide is
17、 intended for use inestimating the relative atmospheric corrosion resistance of aspecific heat of low-alloy steel, based on its chemical compo-sition.5.4 It is important to recognize that the methods presentedhere are based on calculations made from test data for flat,boldly exposed steel specimens.
18、 Atmospheric corrosion ratescan be much higher when the weathering steel remains wet forprolonged periods of time, or is heavily contaminated with saltor other corrosive chemicals. Therefore, caution must beexercised in the application of these methods for prediction oflong-term performance of actua
19、l structures.6. Procedure6.1 Atmospheric corrosion data for the methods presentedhere should be collected in accordance with Practice G50.Specimen preparation, cleaning, and evaluation should con-form to Practice G1.6.2 Linear Regression Extrapolation Method:6.2.1 This method essentially involves th
20、e extrapolation oflogarithmic plots of corrosion losses versus time. Such plots ofatmospheric corrosion data generally fit well to straight lines,and can be represented by equations in slope-intercept form,(3-5):log C 5 log A 1 B log t (1)where:C = corrosion loss,t = time, andA and B = constants. A
21、is the corrosion loss at t = 1, and Bis the slope of a log C versus log + plot.C may be expressed as mass loss per unit area, or as acalculated thickness loss or penetration based on mass loss.6.2.2 The method is best implemented by linear regressionanalysis, using the method of least squares detail
22、ed in GuideG16.At least three data points are required. Once the constantsof the equation are determined by the linear regression analy-sis, the projected corrosion loss can be calculated for any giventime. A sample calculation is shown in Appendix X1.NOTE 2Eq 1 can also be written as follows:C 5 At
23、B(2)Differentiation of Eq 2 with respect to time gives the corrosion rate (R)at any given time:R 5 ABtB 2 1!(3)Also, the time to a given corrosion loss can be calculated as follows:t 5 C/A!1/B(4)6.2.3 Examples of projected atmospheric corrosion lossesover a period of fifty years for low-alloy weathe
24、ring steels invarious environments are presented in Appendix X1.NOTE 3It has been reported (6 and 7) that for some environments, useof log-log linear regression extrapolations may result in predictions whichare somewhat lower or somewhat higher than actual losses. Specifically, inenvironments of ver
25、y low corrosivity, the log-log predictions may behigher than actual losses (6), whereas in environments of very highcorrosivity the opposite may be true (7). For these cases, use of numericaloptimization or composite modeling methods (7 and 8) may provide moreaccurate predictions. Nevertheless, the
26、simpler log-log linear regressionmethod described above provides adequate estimates for most purposes.6.3 Predictive Methods Based on Steel CompositionTwoapproaches are provided for prediction of relative corrosionresistance from composition. The first is based on the data ofLarrabee and Coburn (6.3
27、.1). Its advantage is that it iscomparatively simple to apply. This approach is suitable whenthe alloying elements are limited to Cu, Ni, Cr, Si, and P, andin amounts within the range of the original data. Corrosion3The boldface numbers in parentheses refer to the list of references at the end ofthi
28、s guide.TABLE 1 Constants and Coefficients for Calculating the Rate Constants A and B from CompositionA (m) B (T in months)n 275 227 248 275 227 248site Bethlehem, PA Columbus, OH Pittsburgh, PA Bethlehem, PA Columbus, OH Pittsburgh, PAConstant 15.157 16.143 14.862 0.511 0.539 0.604Carbon 6.310A3.35
29、0 0.102 0.103 0.046ManganeseA2.170 2.370 0.097 0.019 0.042Phosphorus 1.770 10.250 5.120 0.592 0.333 0.546Sulfur 27.200 15.970A2.408 0.908 1.004Silicon 6.50 2.96 1.38 0.20 0.16 0.13Nickel 1.970 1.380 1.180 0.080 0.029 0.088ChromiumA2.560 2.370 0.103 0.095 0.174CopperA0.990 1.970 0.072 0.067 0.068Alum
30、inumA1.580 5.520AA0.087VanadiumA6.110AA0.193ACobalt 1.580 1.770 2.560 0.063 0.053 0.044Arsenic 3.150 6.110 7.690 0.157A0.097MolybdenumAA2.960 0.078 0.038ATin 3.740 7.490 9.860 0.151 0.038ATungstenA5.520A0.148AAACoefficient has greater than 50 % probability of chance occurrence.G101042indices by eith
31、er of the two approaches can be easily deter-mined by use of the tool provided on the ASTM website athttp:/www.astm.org/COMMIT/G01_G101Calculator.xls.6.3.1 Predictive Method Based on the Data of Larabee andCoburnEquations for predicting corrosion loss of low-alloysteels after 15.5 years of exposure
32、to various atmospheres,based on the chemical composition of the steel, were publishedby Legault and Leckie (9). The equations are based onextensive data published by Larrabee and Coburn (10).6.3.1.1 For use in this guide, the Legault-Leckie equationfor an industrial atmosphere (Kearny, N.J.) was mod
33、ified toallow calculation of an atmospheric corrosion resistance indexbased on chemical composition. The modification consisted ofdeletion of the constant and changing the signs of all the termsin the equation. The modified equation for calculation of theatmospheric corrosion resistance index (I) is
34、 given below. Thehigher the index, the more corrosion resistant is the steel.I 5 26.01 % Cu! 1 3.88 % Ni! 1 1.20 % Cr!1 1.49 % Si! 1 17.28 % P! 2 7.29 % Cu! % Ni!2 9.10 % Ni! % P! 2 33.39 % Cu!2NOTE 4Similar indices can be calculated for the Legault-Leckieequations for marine and semi-rural atmosphe
35、res. However, it has beenfound that the ranking of the indices of various steel compositions is thesame for all these equations. Therefore, only one equation is required torank the relative corrosion resistance of different steels.6.3.1.2 The predictive equation should be used only for steelcomposit
36、ions within the range of the original test materials inthe Larrabee-Coburn data set (7). These limits are as follows:Cu 0.51 % maxNi 1.1 % maxCr 1.3 % maxSi 0.64 % maxP 0.12 % max6.3.1.3 Examples of averages and ranges of atmosphericcorrosion resistance indices calculated by the Larrabee-Coburnmetho
37、d for 72 heats of each of two weathering steels are shownin Table X2.1.6.3.2 Predictive Method Based on the Data of TownsendEquations for predicting the corrosion loss of low alloy steelsbased on a statistical analysis of the effects of chemicalcomposition on the corrosion losses of hundreds of stee
38、lsexposed at three industrial locations were published byTownsend (11).6.3.2.1 In this method, the coefficients A and B, as definedfor Eq 1, are calculated as linear combinations of the effects ofeach alloying element, according to Eq 5 and 6.A 5 ao1Saixi(5)B 5 bo1Sbixi(6)where:A and B = constants i
39、n the exponential corrosion lossfunction as defined for Eq 1,aoand bo= constants for three industrial locations as givenin Table 1,aiand bi= constants for each alloying element as given inTable 1 for three industrial locations, andxi= compositions of the individual alloying ele-ments.The A and B val
40、ues calculated from Eq 4 and 5 can be usedto compute corrosion losses, corrosion rates, and times to agiven loss at any of the three sites by use of Eq 2-4,respectively.6.3.2.2 For purposes of calculating a corrosion index fromthe Townsend data, the following procedure shall be followed.(1) For each
41、 of the three test sites, A and B values for pure,unalloyed iron at are calculated by use of the regressionconstants given in Table 1, and Eq 5 and 6.(2) The times for pure iron to reach a 254-m loss at thethree sites are then calculated by use of Eq 4.(3) For a given low alloy steel, A and B values
42、 at each siteare calculated from the regression constants and coefficients inTable 1, and Eq 5 and 6.(4) The losses of the low alloy steel at each site arecalculated from Eq 1 at the times required for pure iron to lose254 m at the same site as determined in (1).(5) The respective differences betwee
43、n the 254-m loss forpure iron and the calculated loss for the low alloy steel at eachsite as determined in (4) are averaged to give a corrosion index.(6) Examples of corrosion indices calculated by theTownsend method are shown in Table 2 for pure iron and avariety of low-alloy steel compositions. Th
44、e upper limit of thecomposition ranges of each element in the Townsend data arealso given in Table 2.6.3.3 The minimum acceptable atmospheric corrosion indexshould be a matter of negotiation between the buyer and theseller.7. Report7.1 When reporting estimates of atmospheric corrosionresistance, the
45、 method of calculation should always be speci-fied.Also, in the Linear Regression Extrapolation Method (6.2)of this guide, the data used should be referenced with respectto type of specimens, condition and location of exposure, andduration of exposure.8. Keywords8.1 atmospheric corrosion resistance;
46、 compositional effects;corrosion indices; high-strength; low-alloy steel; industrialenvironments; marine environments; rural environments;weathering steelsG101043APPENDIXES(Nonmandatory Information)X1. PROJECTED ATMOSPHERIC CORROSION PENETRATIONS FOR WEATHERING STEELSX1.1 Projected atmospheric corro
47、sion losses in fifty yearsfor flat, boldly exposed specimens of Specifications A 588/A 588M and A 242/A 242M Type 1 weathering steels in rural,industrial, and marine environments are shown in Figs. X1.1-X1.3. (The “loss” shown in the figures is the average thicknessloss per surface, calculated from
48、the mass loss per unit area.The uniformity of the thickness loss varies with the type ofenvironment.) These figures were developed from data (12) forspecimens exposed for time periods up to 8 or 16 years invarious countries. The specific exposure locations are given inTables X1.1-X1.3, and the compo
49、sitions of the steels are givenin Table X1.4. In this test program, specimens were exposed infour orientations: 30 to the horizontal facing north and facingsouth, and vertical facing north and facing south. (The backsurface of each specimen was protected with a durable paintsystem.) For the lines plotted in Figs. X1.1-X1.3, data for thetest orientations showing the greatest corrosion losses wereused.X1.2 It must be emphasized that the data shown in Figs.X1.1-X1.3 apply only to flat, boldly exposed specimens.TAB
