ASTM B826-09(2020)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B826 − 09 (Reapproved 2020)
Standard Test Method for
Monitoring Atmospheric Corrosion Tests by Electrical
Resistance Probes
This standard is issued under the fixed designation B826; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year 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. Scope ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 This test method provides a means for monitoring
mendations issued by the World Trade Organization Technical
corrosivity of environmental tests that involve exposure to
Barriers to Trade (TBT) Committee.
corrosive gases.
1.2 This test method uses a resistance monitor (RM) probe 2. Referenced Documents
fabricated from a chosen metal conductor, with one conductor 2
2.1 ASTM Standards:
segment uncovered to permit exposure of the chosen metal
B808 Test Method for Monitoring of Atmospheric Corrosion
conductor to the corrosive gas mixture and the second conduc-
Chambers by Quartz Crystal Microbalances
tor segment covered to protect the metal conductor of this
B810 Test Method for Calibration of Atmospheric Corrosion
segment from direct attack by the corrosive gas mixture. The
Test Chambers by Change in Mass of Copper Coupons
covered conductor segment provides a reference for evaluating
B827 Practice for Conducting Mixed Flowing Gas (MFG)
changes in the uncovered segment. The ratio of the resistance
Environmental Tests
of the exposed segment to that of the covered segment provides
G96 Guide for Online Monitoring of Corrosion in Plant
a measure of the amount of metal conductor that has reacted
Equipment (Electrical and Electrochemical Methods)
with the corrosive gas test environment to form poorly con-
ducting corrosion product, thus providing a measure of test
3. Summary of Test Method
corrosivity.
3.1 The corrosivity of an atmospheric corrosion test such as
1.3 Resistance monitoring is applicable to a broad range of
a mixed flowing gas (MFG) type test is measured by monitor-
test conditions by selection of the appropriate metal conductor ing the loss in electrical conductivity of a metal element whose
and initial metal thickness.
surface corrodes to form poorly conducting corrosion product.
This corrosion product consumes metal from a conduction path
1.4 This method is similar in intent to Test Methods B808.
causing an increase in electrical resistance. The resistance of
1.5 The values stated in SI units are to be regarded as
the degraded conduction path is compared with a similar path
standard. No other units of measurement are included in this
whose surface is covered to prevent corrosion. This compari-
standard.
son resistance also provides a temperature correction reference.
1.6 This standard does not purport to address all of the
The ratio of the electrical resistance of the path exposed to the
safety concerns, if any, associated with its use. It is the
corrosive gases to that of the covered path is monitored during
responsibility of the user of this standard to become familiar
the test and compared to an expected ratio-versus-time curve to
with all hazards including those identified in the appropriate
establish the relationship of the test corrosivity to expected test
Material Safety Data Sheet (MSDS) for this product/material
corrosivity. Alternatively, the ratio-versus-time curve for a
as provided by the manufacturer, to establish appropriate
given atmosphere can be compared with the behavior of other
safety, health, and environmental practices, and determine the
corrosive atmospheres to evaluate the relative corrosivity of the
applicability of regulatory limitations prior to use.
various atmospheres.
1.7 This international standard was developed in accor-
4. Significance and Use
dance with internationally recognized principles on standard-
4.1 Corrosivity monitoring of test environments provides a
means to monitor an integrated value of test corrosivity which
This test method is under the jurisdiction of ASTM Committee B02 on
Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee
B02.05 on Precious Metals and Electrical Contact Materials and Test Methods. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2020. Published October 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1997. Last previous edition approved in 2015 as B826 – 09 (2015). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/B0826-09R20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B826 − 09 (2020)
cannot be evaluated from test parameters themselves, such as form of a serpentine pattern or loop to provide a long conductor
temperature, humidity, and gas concentration. As such the path so as to increase the ease of detection of a resistance
monitor value can be used for specification purposes such as change. With such configurations, formation of a corrosion
test validation. Electrical resistance monitoring of conductors product, which grows out from the edges of the conductor
3,4,5,6
exposed to corrosive media is a well-established practice. paths, can contact adjacent paths; when such contacting cor-
rosion films are formed from conducting corrosion products
4.2 The resistance method assumes uniform corrosion over
such as some copper sulfides, abrupt changes in probe resis-
the entire surface of the exposed metal conductor segment.
tance can be observed due to shorting of the current path. Such
Local corrosion such as pitting, crevice, or grain boundary
shorting of the current path can also occur if condensation
corrosion may provide invalid estimates of test corrosivity.
occurs on the probe, especially in the presence of gases that
Marked changes in slope of the curve of electrical resistance
dissolve in the condensed film to form an electrolyte. Such
ratio versus time may indicate undesired processes which can
shorting behavior is seen as an anomalous resistance decrease
be due to deficiencies in the test atmosphere or in the monitor
and indicates that corrosion of the RM is not predictable from
itself.
its electrical resistance.
4.3 Because of limitations of the diffusion process within
5.2 Corrosive gas permeation through the protective cover-
the corrosion product formed on the metal conductor segment
ing of the reference conductor can lead to corrosion of the
of the RM probe when passivating corrosion films are formed,
reference conductor, thus reducing the apparent resistance ratio
resistance monitoring may not be useful for test chamber
between the exposed conductor and the reference conductor.
monitoring purposes for very long test exposures. Chamber
Excess resistance change of the reference conductor above that
monitoring is dependent on detecting changes in the rate of
expected for any observed temperature change of the RM is an
corrosion of the RM as an indicator signal that specified gas
indication of this possible interference. The RM should be
concentrations must be reverified. However, low corrosion
examined after the test for discoloration of the reference
rates limit the absolute value of the rate of change of corrosion
conductor as a signal of possible corrosion of the reference
rate with change of test conditions; for parabolic film growth
conductor when such excess resistance change is observed.
processes, the growth rate decreases with time limiting the
Presence of corrosion of the reference conductor invalidates
sensitivity of the RM at extended test times.
the estimate of atmosphere corrosivity based on the observed
4.4 Since corrosion rate can be a complex function of test
resistance ratio-versus-time curve.
parameters in MFG tests with any given metal primarily
5.3 Thermal gradients across the RM probe as a result of the
responsive to a subset of the gases in the MFG environment,
presence of local heat sources such as lamps or powered test
more than one type metal resistance probe is required in order
devices can produce an anomalous resistance ratio change.
to assist in maintenance of relative gas concentrations. For
Such effects can be verified by shutting off the local heat source
such test specifications, values of resistance ratios must be
and remeasuring the resistance ratio.
referred to ratios obtained under known test conditions as
supplied by the test specifier. Information relating to the 5.4 Scratches or other localized conductor thickness varia-
sensitivity of various metals to various corrodants has been
tions can produce anomalous resistance ratios after reduced
7,8
published.
corrosion exposures. This behavior can be detected by abrupt
increases in apparent rate of corrosion which occur when the
4.5 RM probes can be useful from 1 % of thickness con-
thinned region corrodes through to the dielectric substrate.
sumed upward to 50 % of thickness consumed by the corrosion
Such abrupt changes indicate the end of useful data from the
film growth. Conductor thicknesses between 25 nm and 0.2
RM.
mm have been reported and common sizes are available
commercially.
5.5 Contaminant films on the surface of the exposed con-
ductor can inhibit corrosion or accelerate corrosion. Care must
5. Interferences
be taken to assure freedom from fingerprints, spittle, oil, or
other surface contamination prior to installation in the test
5.1 Resistance monitor probes are generally constructed
chamber. If a cleaning procedure is used, it should be appro-
from thin film metal coatings on dielectric substrates in the
priately evaluated and consistently applied to avoid differing
initial conditions on the RM. The exposed metal conductor of
3 the probe should be examined after the test exposure to ensure
ASTM G96, Guide for On-Line Monitoring of Corrosion in Plant Equipment
(Electrical and Electrochemical Methods).
uniformity of corrosion film growth. Clumps of corrosion
Allen, R. C. and Trzeciak, M. J., “Measuring Environmental Corrosivity,”
product indicate undesirable conditions and potential problems
Institute of Electrical and Electronic Engineers, Components, Hybrids, and Manu-
interpreting resistance changes.
facturing Technology Transaction, Vol CHMT-3, 1, March 1980, pp. 67-70.
Murcko, R., Corros
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