ASTM G16-95(2004)

Standard Guide for Applying Statistics to Analysis of Corrosion Data

SIGNIFICANCE AND USE
Corrosion test results often show more scatter than many other types of tests because of a variety of factors, including the fact that minor impurities often play a decisive role in controlling corrosion rates. Statistical analysis can be very helpful in allowing investigators to interpret such results, especially in determining when test results differ from one another significantly. This can be a difficult task when a variety of materials are under test, but statistical methods provide a rational approach to this problem.
Modern data reduction programs in combination with computers have allowed sophisticated statistical analyses on data sets with relative ease. This capability permits investigators to determine if associations exist between many variables and, if so, to develop quantitative expressions relating the variables.
Statistical evaluation is a necessary step in the analysis of results from any procedure which provides quantitative information. This analysis allows confidence intervals to be estimated from the measured results.
SCOPE
1.1 This guide presents briefly some generally accepted methods of statistical analyses which are useful in the interpretation of corrosion test results.
1.2 This guide does not cover detailed calculations and methods, but rather covers a range of approaches which have found application in corrosion testing.
1.3 Only those statistical methods that have found wide acceptance in corrosion testing have been considered in this guide.

General Information

• Status: Historical
• Publication Date: 30-Apr-2004
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.05 - Laboratory Corrosion Tests

Relations

• Replaces: ASTM G16-95(1999)e1 - Standard Guide for Applying Statistics to Analysis of Corrosion Data
• Effective Date: 01-May-2004
• Replaced By: ASTM G16-95(2010) - Standard Guide for Applying Statistics to Analysis of Corrosion Data
• Effective Date: 01-Feb-2010
• Referred By: ASTM G202-12(2020) - Standard Test Method for Using Atmospheric Pressure Rotating Cage
• Effective Date: 01-May-2004
• Referred By: ASTM C1187-20a - Standard Guide for Establishing Surveillance Test Program for Boron-based Neutron Absorbing Material Systems for Use in Nuclear Fuel Storage Racks in Pool Environment
• Effective Date: 01-May-2004
• Referred By: ASTM G46-21 - Standard Guide for Examination and Evaluation of Pitting Corrosion
• Effective Date: 01-May-2004
• Referred By: ASTM F3044-20 - Standard Test Method for Evaluating the Potential for Galvanic Corrosion for Medical Implants
• Effective Date: 01-May-2004
• Referred By: ASTM G116-99(2020)e1 - Standard Practice for Conducting Wire-on-Bolt Test for Atmospheric Galvanic Corrosion
• Effective Date: 01-May-2004
• Referred By: ASTM G71-81(2019) - Standard Guide for Conducting and Evaluating Galvanic Corrosion Tests in Electrolytes
• Effective Date: 01-May-2004
• Referred By: ASTM D4778-15 - Standard Test Method for Determination of Corrosion and Fouling Tendency of Cooling Water Under Heat Transfer Conditions
• Effective Date: 01-May-2004
• Referred By: ASTM F3268-18a - Standard Guide for <emph type="bdit">in vitro</emph> Degradation Testing of Absorbable Metals
• Effective Date: 01-May-2004
• Referred By: ASTM G208-12(2020) - Standard Practice for Evaluating and Qualifying Oilfield and Refinery Corrosion Inhibitors Using Jet Impingement Apparatus
• Effective Date: 01-May-2004
• Referred By: ASTM G185-06(2020)e1 - Standard Practice for Evaluating and Qualifying Oil Field and Refinery Corrosion Inhibitors Using the Rotating Cylinder Electrode
• Effective Date: 01-May-2004
• Referred By: ASTM G123-00(2022)e1 - Standard Test Method for Evaluating Stress-Corrosion Cracking of Stainless Alloys with Different Nickel Content in Boiling Acidified Sodium Chloride Solution
• Effective Date: 01-May-2004
• Referred By: ASTM C1617-19 - Standard Practice for Quantitative Accelerated Laboratory Evaluation of Extraction Solutions Containing Ions Leached from Thermal Insulation on Aqueous Corrosion of Metals
• Effective Date: 01-May-2004
• Referred By: ASTM G217-16(2022) - Standard Guide for Corrosion Monitoring in Laboratories and Plants with Coupled Multielectrode Array Sensor Method
• Effective Date: 01-May-2004

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information.
Designation:G16–95 (Reapproved 2004)
Standard Guide for
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Applying Statistics to Analysis of Corrosion Data
ThisstandardisissuedunderthefixeddesignationG16;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2 Modern data reduction programs in combination with
computers have allowed sophisticated statistical analyses on
1.1 This guide presents briefly some generally accepted
data sets with relative ease. This capability permits investiga-
methods of statistical analyses which are useful in the inter-
tors to determine if associations exist between many variables
pretation of corrosion test results.
and, if so, to develop quantitative expressions relating the
1.2 This guide does not cover detailed calculations and
variables.
methods, but rather covers a range of approaches which have
3.3 Statistical evaluation is a necessary step in the analysis
found application in corrosion testing.
of results from any procedure which provides quantitative
1.3 Only those statistical methods that have found wide
information. This analysis allows confidence intervals to be
acceptance in corrosion testing have been considered in this
estimated from the measured results.
guide.
4. Errors
2. Referenced Documents
2
4.1 Distributions—In the measurement of values associated
2.1 ASTM Standards:
withthecorrosionofmetals,avarietyoffactorsacttoproduce
E178 Practice for Dealing With Outlying Observations
measured values that deviate from expected values for the
E380 Practice for Use of the International System of Units
3
conditions that are present. Usually the factors which contrib-
(SI) (the Modernized Metric System)
utetotheerrorofmeasuredvaluesactinamoreorlessrandom
E691 Practice for Conducting an Interlaboratory Study to
way so that the average of several values approximates the
Determine the Precision of a Test Method
expected value better than a single measurement. The pattern
G46 Guide for Examination and Evaluation of Pitting
in which data are scattered is called its distribution, and a
Corrosion
variety of distributions are seen in corrosion work.
3. Significance and Use 4.2 Histograms—A bar graph called a histogram may be
used to display the scatter of the data. A histogram is
3.1 Corrosion test results often show more scatter than
constructed by dividing the range of data values into equal
many other types of tests because of a variety of factors,
intervals on the abscissa axis and then placing a bar over each
including the fact that minor impurities often play a decisive
interval of a height equal to the number of data points within
role in controlling corrosion rates. Statistical analysis can be
thatinterval.Thenumberofintervalsshouldbefewenoughso
very helpful in allowing investigators to interpret such results,
that almost all intervals contain at least three points, however
especially in determining when test results differ from one
there should be a sufficient number of intervals to facilitate
anothersignificantly.Thiscanbeadifficulttaskwhenavariety
visualization of the shape and symmetry of the bar heights.
of materials are under test, but statistical methods provide a
Twenty intervals are usually recommended for a histogram.
rational approach to this problem.
Because so many points are required to construct a histogram,
it is unusual to find data sets in corrosion work that lend
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themselves to this type of analysis.
This guide is under the jurisdiction ofASTM Committee G01 on Corrosion of
Metals and is the direct responsibility of Subcommittee G01.05 on Laboratory
4.3 Normal Distribution—Many statistical techniques are
Corrosion Tests.
based on the normal distribution. This distribution is bell-
Current edition approved May 1, 2004. Published May 2004. Originally
´1 shapedandsymmetrical.Useofanalysistechniquesdeveloped
approved in 1971. Last previous edition approved in 1999 as G16–95 (1999) .
for the normal distribution on data distributed in another
DOI: 10.1520/G0016-95R04.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
mannercanleadtogrosslyerroneousconclusions.Thus,before
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
attempting data analysis, the data should either be verified as
Standards volume information, refer to the standard’s Document Summary page on
being scattered like a normal distribution, or a transformation
the ASTM website.
3
Withdrawn. should be used to obtain a data set which is approximately
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