ASTM B827-97(2003)
(Practice)Standard Practice for Conducting Mixed Flowing Gas (MFG) Environmental Tests
Standard Practice for Conducting Mixed Flowing Gas (MFG) Environmental Tests
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 the 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 for this product/material as provided by the manufacturer, to establish appropriate safety and health practices, and determine the applicability of regulatory limitations prior to use. See 5.1.2.4.
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Designation:B827–97(Reapproved2003)
Standard Practice for
Conducting Mixed Flowing Gas (MFG) Environmental Tests
This standard is issued under the fixed designation B 827; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope B 825 Test Method for Coulometric Reduction of Surface
Films on Metallic Test Samples
1.1 This practice provides procedures for conducting envi-
B 826 Test Method for Monitoring Atmospheric Corrosion
ronmental tests involving exposures to controlled quantities of
Tests by Electrical Resistance Probes
corrosive gas mixtures.
B 845 Guide for Mixed Flowing Gas (MFG) Tests for
1.2 This practice provides for the required equipment and
Electrical Contacts
methods for gas, temperature, and humidity control which
D 1193 Specification for Reagent Water
enable tests to be conducted in a reproducible manner. Repro-
D 1607 Test Method for Nitrogen Dioxide Content of the
ducibility is measured through the use of control coupons
Atmosphere (Griess-Saltzman Reaction)
whose corrosion films are evaluated by mass gain, coulometry,
D 2912 Test Method for Oxidant Content of the Atmo-
or by various electron and X-ray beam analysis techniques.
sphere (Neutral KI)
Reproducibility can also be measured by in situ corrosion rate
D 2914 Test Methods for Sulfur Dioxide Content of the
monitors using electrical resistance or mass/frequency change
Atmosphere (West-Gaeke Method)
methods.
D 3449 Test Method for Sulfur Dioxide in Workplace At-
1.3 The values stated in SI units are to be regarded as the
mospheres (Barium Perchlorate Method)
standard.
D 3464 Test Method forAverageVelocity in a Duct Using a
1.4 This standard does not purport to address all of the
Thermal Anemometer
safety concerns, if any, associated with its use. It is the
D 3609 Practice for Calibration Techniques Using Perme-
responsibility of the user of this standard to become familiar
ation Tubes
with all hazards including those identified in the appropriate
D 3824 Test Methods for Continuous Measurement of Ox-
Material Safety Data Sheet for this product/material as pro-
ides of Nitrogen in theAmbient or WorkplaceAtmosphere
vided by the manufacturer, to establish appropriate safety and
by the Chemiluminescent Method
health practices, and determine the applicability of regulatory
D 4230 Test Method of Measuring Humidity With Cooled-
limitations prior to use. See 5.1.2.4.
Surface Condensation (Dew-Point) Hygrometer
2. Referenced Documents E 902 Practice for Checking the Operating Characteristics
of X-Ray Photoelectron Spectrometers
2.1 ASTM Standards:
G 91 Practice for Monitoring Atmospheric SO Using Sul-
B 542 Terminology Relating to Electrical Contacts and 2
fation Plate Technique
Their Use
B 765 Guide for Selection of Porosity Tests for Electrode-
3. Terminology
posits and Related Metallic Coatings
3.1 Definitions relating to electrical contacts are in accor-
B 808 Test Method for Monitoring of Atmospheric Corro-
2 dance with Terminology B 542.
sion Chambers by Quartz Crystal Microbalances
B 810 Test Method for Calibration of Atmospheric Corro-
4. Significance and Use
sion Test Chambers by Change in Mass of Copper Cou-
2 4.1 Mixed flowing gas (MFG) tests are used to simulate or
pons
amplify exposure to environmental conditions which electrical
This practice is under the jurisdiction ofASTM Committee B02 on Nonferrous
Metals and Alloys and is the direct responsibility of Subcommittee B02.11 on
Electrical Contact Test Methods. Annual Book of ASTM Standards, Vol 11.01.
Current edition approved June 10, 2003. Published July 2003. Originally Annual Book of ASTM Standards, Vol 11.03.
approved in 1992. Last previous edition approved in 1997 as B 827 - 97. Discontinued; see 1990 Annual Book of ASTM Standards, Vol 11.03.
2 7
Annual Book of ASTM Standards, Vol 02.04. Annual Book of ASTM Standards, Vol 03.06.
3 8
Annual Book of ASTM Standards, Vol 02.05. Annual Book of ASTM Standards, Vol 03.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B827–97 (2003)
contactsorconnectorscanbeexpectedtoexperienceinvarious ture to a maximum tolerance of 61°C with a preferred
application environments (1, 2). tolerance held to 60.5°C within the usable chamber working
4.2 Test samples which have been exposed to MFG tests space accordance with 7.3, with a means to introduce and
have ranged from bare metal surfaces, to electrical connectors, exhaust gases from the chamber.
and to complete assemblies.
5.1.1.2 The chamber isolates the reactive gases from the
4.3 The specific test conditions are usually chosen so as to
external environment. Chamber materials that are not low-
simulate, in the test laboratory, the effects of certain represen-
absorbing can affect test conditions by absorbing or emitting
tative field environments or environmental severity levels on
reactive gases, leading to control and reproducibility problems.
standard metallic surfaces, such as copper and silver coupons
Thechamberconstructionshallbesuchthattheleakrateisless
or porous gold platings (1, 2).
than 3 % of the volume exchange rate.
4.4 Because MFG tests are simulations, both the test con-
5.1.1.3 The chamber shall have provision for maintaining
ditions and the degradation reactions (chemical reaction rate,
uniformity of the average gas flow velocity within 620%ofa
composition of reaction products, etc.) may not always re-
specified value or of the chamber average when the chamber is
semble those found in the service environment of the product
empty. For chambers with a dimension of more than 0.5 m,
being tested in the MFG test. A guide to the selection of
measurement points shall be in accordance with Test Method
simulation conditions suitable for a variety of environments is
B 810. For chambers with all dimensions of less than 0.5 m, a
found in Guide B 845.
minimum of five points shall be measured at locations in the
4.5 The MFG exposures are generally used in conjunction
plane of sample exposure (perpendicular to the expected flow
with procedures which evaluate contact or connector electrical
direction) that are equidistant from each other and the walls of
performance such as measurement of electrical contact resis-
the chamber.After all five or more data values are recorded, all
tance before and after MFG exposure.
measurements shall be repeated a second time. After the two
4.6 The MFG tests are useful for connector systems whose
setsofmeasurementsarerecorded,athirdcompletesetshallbe
contact surfaces are plated or clad with gold or other precious
recorded. The arithmetic average of the 15 or more measure-
metal finishes. For such surfaces, environmentally produced
ments shall be the chamber average. See 7.5 and 7.6.8. If a hot
failures are often due to high resistance or intermittences
wire anemometer is used for gas velocity measurements, it
caused by the formation of insulating contamination in the
shall be made in accordance with Test Method D 3464, with
contact region. This contamination, in the form of films and
the exception that sample sites shall be in accordance withTest
hard particles, is generally the result of pore corrosion and
Method B 810.
corrosion product migration or tarnish creepage from pores in
5.1.1.4 A sample access port is desirable. This should be
the precious metal coating and from unplated base metal
designedsuchthatcontrolcouponscanberemovedorreplaced
boundaries, if present.
without interrupting the flow of gases. Corrosion test chamber
4.7 The MFG exposures can be used to evaluate novel
corrosion rates have been shown to be a function of the
electricalcontactmetallizationforsusceptibilitytodegradation
presenceorabsenceoflight(3,4).Provisionforcontrollingthe
due to environmental exposure to the test corrosive gases.
test illumination level in accordance with a test specification
4.8 The MFG exposures can be used to evaluate the
shall be made.
shielding capability of connector housings which may act as a
5.1.1.5 Examples of test chamber systems are diagrammed
barrier to the ingress of corrosive gases.
in Figs. 1-3.They are not to be considered exclusive examples.
4.9 The MFG exposures can be used to evaluate the
5.1.2 Gas Supply System:
susceptibility of other connector materials such as plastic
5.1.2.1 Description and Requirements—Thegassupplysys-
housings to degradation from the test corrosive gases.
tem consists of five main parts: a source of clean, dry, filtered
4.10 The MFG tests are not normally used as porosity tests.
air; a humidity source; corrosive gas source(s); gas delivery
For a guide to porosity testing, see Guide B 765.
system; and corrosive gas concentration monitoring system(s).
4.11 The MFG tests are generally not applicable where the
Total supply capacity must be such as to meet requirements for
failure mechanism is other than pollutant gas corrosion such as
controlofgasconcentrations.Theminimumnumberofvolume
in tin-coated separable contacts.
changes is determined by the requirement that the concentra-
5. Apparatus tion of corrosive gases be maintained within 615 % between
gas inlet and outlet. This is verified by measurement of the gas
5.1 Apparatus required to conduct MFG tests are divided
concentrations near the gas inlet upstream of the usable
into four major categories, corrosion test chamber, gas supply
chamber working volume and comparing with gas concentra-
system, chamber monitoring system, and chamber operating
tions measured downstream of the usable chamber working
system.
volume just prior to the chamber exhaust; these values shall be
5.1.1 Corrosion Test Chamber:
within 615 % (see 7.6).Alternative methods of demonstrating
5.1.1.1 The chamber shall consist of an enclosure made of
compliance with the maximum allowable concentration gradi-
nonreactive, low-absorbing, nonmetallic materials contained
ent are acceptable. Normally, a conditioned chamber equili-
within a cabinet or oven capable of maintaining the tempera-
brateswithinseveralhoursaftersampleloadingandstartofthe
corrosivegassupply.Timeslongerthan2hshallbereportedin
the test report; see Section 8. A guide to estimating supply
The boldface numbers in parentheses refer to the list of references at the end of
this standard. requirements is provided in Appendix X1.
B827–97 (2003)
This practice involves the use of hazardous materials, proce-
dures, and equipment. The gas concentrations in the test
chamber may be within permissible exposure limits (PEL).
However, concentrations in the compressed gas cylinders 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
concentration control and may introduce corrosion processes
whicharenotrepresentativeofgaseouscorrosionmechanisms.
Aerosol formation may be detected by the presence of a visible
film or deposit on the interior surface of the gas system where
the gases are mixed.
(3) Any fogging of the tubing walls or mixing chamber
FIG. 1 Schematic Flow-Through Mixed Flowing Gas (MFG) Test
System
walls can be taken to be an indication of a loss of corrosive
gases from the atmosphere. Final mixing of the specified gases
NOTE 1—Guidance: when inlet to outlet concentrations vary by more should occur inside a separate area of, or as close as possible
than 615 %, it usually indicates an overloaded chamber.
to, the test chamber so as to ensure thermal equilibration with
the test chamber.
5.1.2.2 Clean, Dry, Filtered Air Source— Gases other than
(4) Flow measurement capability is required at the inlet of
oxygen and nitrogen that are present in the dry air source shall
the chamber and also at the exhaust of negative pressure
be less than or equal to those defined by OHSAClass D limits
chambers to ensure the absence of uncalibrated gas streams.
with the following additional constraint. Gases other than
5.1.2.6 Corrosive Gas Concentration Monitoring System—
nitrogen, oxygen, carbon dioxide, noble gases, methane, ni-
Standard measurement systems for very low level gas concen-
trous oxide, and hydrogen shall be less than 0.005 (ppm) by
trations are listed in Table 1, which provides for gases in
volumetotalandshallbeHighEfficiencyParticulateArrestants
common use in present mixed flowing gas systems, for testing
(HEPA) filtered.
electrical contact performance.
5.1.2.3 Humidity Source—The humidity source shall use
(1) Each instrument must be characterized for interference
distilled or deionized water, Specification D 1193, Type 1 or
better, and shall introduce no extraneous material. The humid- with the gases specified, both individually and mixed.
ity source shall be maintained equivalent to Specification (2) Depending on the exact equipment set used, it may not
D 1193 Type II or better, with the exception that electrical be possible to accurately measure the concentration of some
resistivity shall be maintained equivalent to Specification
gases, such as chlorine, in combination with any of the other
D 1193 Type IV. The time averaged value of humidity shall be gases.
within 61 % relative humidity of the specified value with
(3) The analytic instruments shall be maintained and
absolute variations no greater than 63 % relative humidity
calibrated electronically in accordance with the manufacturers’
from the specified value.
recommendations.Standardgassourcesshallalsobecalibrated
5.1.2.4 Corrosive Gas Sources—Corrosive (test) gases,
in accordance with the manufacturers’ specifications, or in
such as nitrogen dioxide, hydrogen sulfide, chlorine, sulfur
accordance with Practice D 3609. Gas concentration analyzers
dioxide, etc. shall be of chemically pure grade or better. Such
shall be calib
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