ASTM B827-05(2020)
(Practice)Standard Practice for Conducting Mixed Flowing Gas (MFG) Environmental Tests
Standard Practice for Conducting Mixed Flowing Gas (MFG) Environmental Tests
SIGNIFICANCE AND USE
4.1 Mixed flowing gas (MFG) tests are used to simulate or amplify exposure to environmental conditions which electrical contacts or connectors can be expected to experience in various application environments (1, 2).4
4.2 Test samples which have been exposed to MFG tests have ranged from bare metal surfaces, to electrical connectors, and to complete assemblies.
4.3 The specific test conditions are usually chosen so as to simulate, in the test laboratory, the effects of certain representative field environments or environmental severity levels on standard metallic surfaces, such as copper and silver coupons or porous gold platings (1, 2).
4.4 Because MFG tests are simulations, both the test conditions and the degradation reactions (chemical reaction rate, composition of reaction products, etc.) may not always resemble those found in the service environment of the product being tested in the MFG test. A guide to the selection of simulation conditions suitable for a variety of environments is found in Guide B845.
4.5 The MFG exposures are generally used in conjunction with procedures which evaluate contact or connector electrical performance such as measurement of electrical contact resistance before and after MFG exposure.
4.6 The MFG tests are useful for connector systems whose contact surfaces are plated or clad with gold or other precious metal finishes. For such surfaces, environmentally produced failures are often due to high resistance or intermittences caused by the formation of insulating contamination in the contact region. This contamination, in the form of films and hard particles, is generally the result of pore corrosion and corrosion product migration or tarnish creepage from pores in the precious metal coating and from unplated base metal boundaries, if present.
4.7 The MFG exposures can be used to evaluate novel electrical contact metallization for susceptibility to degradation due to environmental exposure to the test corrosive gases...
SCOPE
1.1 This practice provides procedures for conducting environmental tests involving exposures to controlled quantities of corrosive gas mixtures.
1.2 This practice provides for the required equipment and methods for gas, temperature, and humidity control which enable tests to be conducted in a reproducible manner. Reproducibility is measured through the use of control coupons whose corrosion films are evaluated by mass gain, coulometry, or by various electron and X-ray beam analysis techniques. Reproducibility can also be measured by in situ corrosion rate monitors using electrical resistance or mass/frequency change methods.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to become familiar with all hazards including those identified in the appropriate Material Safety Data Sheet (MSDS) for this product/material as provided by the manufacturer, to establish appropriate safety, health, and environmental practices, and determine the applicability of regulatory limitations prior to use. See 5.1.2.4.
1.5 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.
General Information
Relations
Standards Content (Sample)
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: B827 − 05 (Reapproved 2020)
Standard Practice for
Conducting Mixed Flowing Gas (MFG) Environmental Tests
This standard is issued under the fixed designation B827; 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 B542 Terminology Relating to Electrical Contacts and Their
Use
1.1 This practice provides procedures for conducting envi-
B765 Guide for Selection of Porosity and Gross Defect Tests
ronmental tests involving exposures to controlled quantities of
for Electrodeposits and Related Metallic Coatings
corrosive gas mixtures.
B808 Test Method for Monitoring of Atmospheric Corrosion
1.2 This practice provides for the required equipment and
Chambers by Quartz Crystal Microbalances
methods for gas, temperature, and humidity control which
B810 Test Method for Calibration of Atmospheric Corrosion
enable tests to be conducted in a reproducible manner. Repro-
Test Chambers by Change in Mass of Copper Coupons
ducibility is measured through the use of control coupons
B825 Test Method for Coulometric Reduction of Surface
whose corrosion films are evaluated by mass gain, coulometry,
Films on Metallic Test Samples
or by various electron and X-ray beam analysis techniques.
B826 Test Method for Monitoring Atmospheric Corrosion
Reproducibility can also be measured by in situ corrosion rate
Tests by Electrical Resistance Probes
monitors using electrical resistance or mass/frequency change
B845 Guide for Mixed Flowing Gas (MFG) Tests for Elec-
methods.
trical Contacts
1.3 The values stated in SI units are to be regarded as
D1193 Specification for Reagent Water
standard. No other units of measurement are included in this
D2912 Test Method for Oxidant Content of the Atmosphere
standard.
(Neutral Ki) (Withdrawn 1990)
1.4 This standard does not purport to address all of the
D2914 Test Methods for Sulfur Dioxide Content of the
safety concerns, if any, associated with its use. It is the
Atmosphere (West-Gaeke Method)
responsibility of the user of this standard to become familiar
D3449 Test Method for Sulfur Dioxide in Workplace Atmo-
with all hazards including those identified in the appropriate
spheres (Barium Perchlorate Method) (Withdrawn 1989)
Material Safety Data Sheet (MSDS) for this product/material
D3464 Test Method for Average Velocity in a Duct Using a
as provided by the manufacturer, to establish appropriate
Thermal Anemometer
safety, health, and environmental practices, and determine the
D3609 Practice for Calibration Techniques Using Perme-
applicability of regulatory limitations prior to use. See 5.1.2.4.
ation Tubes
1.5 This international standard was developed in accor-
D3824 Test Methods for Continuous Measurement of Ox-
dance with internationally recognized principles on standard-
ides of Nitrogen in the Ambient or Workplace Atmosphere
ization established in the Decision on Principles for the
by Chemiluminescence
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical D4230 Test Method for Measuring Humidity with Cooled-
Barriers to Trade (TBT) Committee. Surface Condensation (Dew-Point) Hygrometer
E902 Practice for Checking the Operating Characteristics of
2. Referenced Documents
X-Ray Photoelectron Spectrometers (Withdrawn 2011)
2.1 ASTM Standards: G91 Practice for Monitoring Atmospheric SO Deposition
Rate for Atmospheric Corrosivity Evaluation
This practice is under the jurisdiction of ASTM Committee B02 on Nonferrous
3. Terminology
Metals and Alloys and is the direct responsibility of Subcommittee B02.05 on
Precious Metals and Electrical Contact Materials and Test Methods.
3.1 Definitions relating to electrical contacts are in accor-
Current edition approved April 1, 2020. Published April 2020. Originally
dance with Terminology B542.
approved in 1992. Last previous edition approved in 2014 as B827 – 05 (2014).
DOI: 10.1520/B0827-05R20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B827 − 05 (2020)
4. Significance and Use 5. Apparatus
4.1 Mixed flowing gas (MFG) tests are used to simulate or 5.1 Apparatus required to conduct MFG tests are divided
into four major categories, corrosion test chamber, gas supply
amplify exposure to environmental conditions which electrical
system, chamber monitoring system, and chamber operating
contacts or connectors can be expected to experience in various
system.
application environments (1, 2).
5.1.1 Corrosion Test Chamber:
4.2 Test samples which have been exposed to MFG tests
5.1.1.1 The chamber shall consist of an enclosure made of
have ranged from bare metal surfaces, to electrical connectors,
nonreactive, low-absorbing, nonmetallic materials contained
and to complete assemblies.
within a cabinet or oven capable of maintaining the tempera-
4.3 The specific test conditions are usually chosen so as to
ture to a maximum tolerance of 61°C with a preferred
simulate, in the test laboratory, the effects of certain represen-
tolerance held to 60.5°C within the usable chamber working
tative field environments or environmental severity levels on space accordance with 7.3, with a means to introduce and
standard metallic surfaces, such as copper and silver coupons exhaust gases from the chamber.
or porous gold platings (1, 2).
5.1.1.2 The chamber isolates the reactive gases from the
external environment. Chamber materials that are not low-
4.4 Because MFG tests are simulations, both the test con-
absorbing can affect test conditions by absorbing or emitting
ditions and the degradation reactions (chemical reaction rate,
reactive gases, leading to control and reproducibility problems.
composition of reaction products, etc.) may not always re-
The chamber construction shall be such that the leak rate is less
semble those found in the service environment of the product
than 3 % of the volume exchange rate.
being tested in the MFG test. A guide to the selection of
5.1.1.3 The chamber shall have provision for maintaining
simulation conditions suitable for a variety of environments is
uniformity of the average gas flow velocity within 620 % of a
found in Guide B845.
specified value or of the chamber average when the chamber is
4.5 The MFG exposures are generally used in conjunction
empty. For chambers with a dimension of more than 0.5 m,
with procedures which evaluate contact or connector electrical
measurement points shall be in accordance with Test Method
performance such as measurement of electrical contact resis- B810. For chambers with all dimensions of less than 0.5 m, a
tance before and after MFG exposure.
minimum of five points shall be measured at locations in the
plane of sample exposure (perpendicular to the expected flow
4.6 The MFG tests are useful for connector systems whose
direction) that are equidistant from each other and the walls of
contact surfaces are plated or clad with gold or other precious
the chamber. After all five or more data values are recorded, all
metal finishes. For such surfaces, environmentally produced
measurements shall be repeated a second time. After the two
failures are often due to high resistance or intermittences
sets of measurements are recorded, a third complete set shall be
caused by the formation of insulating contamination in the
recorded. The arithmetic average of the 15 or more measure-
contact region. This contamination, in the form of films and
ments shall be the chamber average. See 7.5 and 7.6.8. If a hot
hard particles, is generally the result of pore corrosion and
wire anemometer is used for gas velocity measurements, it
corrosion product migration or tarnish creepage from pores in
shall be made in accordance with Test Method D3464, with the
the precious metal coating and from unplated base metal
exception that sample sites shall be in accordance with Test
boundaries, if present.
Method B810.
5.1.1.4 A sample access port is desirable. This should be
4.7 The MFG exposures can be used to evaluate novel
electrical contact metallization for susceptibility to degradation designed such that control coupons can be removed or replaced
without interrupting the flow of gases. Corrosion test chamber
due to environmental exposure to the test corrosive gases.
corrosion rates have been shown to be a function of the
4.8 The MFG exposures can be used to evaluate the
presence or absence of light (3, 4). Provision for controlling the
shielding capability of connector housings which may act as a
test illumination level in accordance with a test specification
barrier to the ingress of corrosive gases.
shall be made.
5.1.1.5 Examples of test chamber systems are diagrammed
4.9 The MFG exposures can be used to evaluate the
susceptibility of other connector materials such as plastic in Figs. 1-3. They are not to be considered exclusive examples.
housings to degradation from the test corrosive gases.
5.1.2 Gas Supply System:
5.1.2.1 Description and Requirements—The gas supply sys-
4.10 The MFG tests are not normally used as porosity tests.
tem consists of five main parts: a source of clean, dry, filtered
For a guide to porosity testing, see Guide B765.
air; a humidity source; corrosive gas source(s); gas delivery
4.11 The MFG tests are generally not applicable where the
system; and corrosive gas concentration monitoring system(s).
failure mechanism is other than pollutant gas corrosion such as
Total supply capacity must be such as to meet requirements for
in tin-coated separable contacts.
control of gas concentrations. The minimum number of volume
changes is determined by the requirement that the concentra-
tion of corrosive gases be maintained within 615 % between
gas inlet and outlet. This is verified by measurement of the gas
The boldface numbers in parentheses refer to the list of references at the end of
this standard. concentrations near the gas inlet upstream of the usable
B827 − 05 (2020)
absolute variations no greater than 63 % relative humidity
from the specified value.
5.1.2.4 Corrosive Gas Sources—Corrosive (test) gases, such
as nitrogen dioxide, hydrogen sulfide, chlorine, sulfur dioxide,
etc. shall be of chemically pure grade or better. Such gases are
frequently supplied in dry carrier gas such as nitrogen or air.
(Warning—This practice involves the use of hazardous
materials, procedures, and equipment. The gas concentrations
in the test chamber may be within permissible exposure limits
(PEL). However, concentrations in the compressed gas cylin-
ders or permeation devices are often above the PEL, and may
exceed the immediately dangerous to life and health level
(IDHL). This practice does not address safety issues associated
with MFG testing.)
5.1.2.5 Gas Delivery System—The gas delivery system is
comprised of three main parts: gas supply lines, gas control
valves and flow controllers, and a mixing chamber. The gas
delivery system shall be capable of delivering gases at the
required concentrations and rates within the test chamber.
(1) All materials used for the gas transport system must not
interact with the gases to the extent that chamber gas concen-
trations are affected.
(2) Gases, make-up air, and water vapor must be thor-
oughly mixed before gas delivery to the samples under test in
the chambers. Care must be taken to ensure absence of aerosol
formation in the mixing chamber whereby gases are consumed
in the formation of particulates which may interfere with gas
FIG. 1 Schematic Flow-Through Mixed Flowing Gas (MFG) Test
concentration control and may introduce corrosion processes
System
which are not representative of gaseous corrosion mechanisms.
Aerosol formation may be detected by the presence of a visible
film or deposit on the interior surface of the gas system where
chamber working volume and comparing with gas concentra-
the gases are mixed.
tions measured downstream of the usable chamber working
(3) Any fogging of the tubing walls or mixing chamber
volume just prior to the chamber exhaust; these values shall be
walls can be taken to be an indication of a loss of corrosive
within 615 % (see 7.6). Alternative methods of demonstrating
gases from the atmosphere. Final mixing of the specified gases
compliance with the maximum allowable concentration gradi-
should occur inside a separate area of, or as close as possible
ent are acceptable. Normally, a conditioned chamber equili-
to, the test chamber so as to ensure thermal equilibration with
brates within several hours after sample loading and start of the
the test chamber.
corrosive gas supply. Times longer than 2 h shall be reported in
(4) Flow measurement capability is required at the inlet of
the test report; see Section 8. A guide to estimating supply
the chamber and also at the exhaust of negative pressure
requirements is provided in Appendix X1.
chambers to ensure the absence of uncalibrated gas streams.
NOTE 1—Guidance: when inlet to outlet concentrations vary by more
5.1.2.6 Corrosive Gas Concentration Monitoring System—
than 615 %, it usually indicates an overloaded chamber.
Standard measurement systems for very low level gas concen-
5.1.2.2 Clean, Dry, Filtered Air Source—Gases other than
trations are listed in Table 1, which provides for gases in
oxygen and nitrogen that are present in the dry air source shall
common use in present mixed flowing gas systems, for testing
be less than or equal to those defined by OHSA Class D limits
electrical contact performance.
with the following additional constraint. Gases other than
(1) Each instrument must be characterized for interference
nitrogen, oxygen, carbon dioxide, noble gases, methane, ni-
with the gases specified, both individually and mixed.
trous oxide, and hydrogen shall be less than 0.005 (ppm) by
(2) Depending on the exact equipment set used, it may not
volume total and shall be High Efficiency Particulate Arrestants
be possible to accurately measure the concentration of some
(HEPA) filtered.
gases, such as chlorine, in combination with any of the other
5.1.2.3 Humidity Source—T
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.