ASTM A1071/A1071M-11

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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: A1071/A1071M − 11
StandardTest Method for
Evaluating Hygrothermal Corrosion Resistance of
Permanent Magnet Alloys
This standard is issued under the fixed designation A1071/A1071M; 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 3.1.1 bulk corrosion test (BCT) grade, n—grade given to
ranges of specific weight loss to indicate the relative corrosion
1.1 This test method covers the equipment, procedures, and
resistance of a material. (The grades are listed in 15.2.)
measurement of the resistance of permanent magnet alloys
against corrosion in high temperature, high pressure water 3.1.2 specific weight loss, n—weight loss of the specimen
vapor environments. This test is also known as the Bulk per unit of exposed surface area, in units of milligrams per
Corrosion Test (BCT). square centimetre, due to corrosion and disintegration.
1.2 The values and equations stated in customary (cgs-emu
4. Summary of Test Method
and inch-pound) units or SI units are to be regarded separately
as standard. Within this standard the SI units, when different
4.1 Permanent magnet samples are exposed to pressurized
from customary units, are shown in brackets, the values stated
steam to determine the resistance of these materials, especially
in each system may not be exact equivalents; therefore, each
rare earth-type permanent magnets, to degradation by the
system shall be used independently of the other. Combining
combined action of heat and water vapor. The resulting weight
values from the two systems may result in nonconformance
loss (including removed loosely-attached material) is used to
with this standard.
rate the hygrothermal corrosion resistance of the magnet.
1.3 This standard does not purport to address all of the
5. Significance and Use
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5.1 This test method provides a controlled corrosive envi-
priate safety and health practices and determine the applica-
ronment which can be utilized to produce relative corrosion
bility of regulatory limitations prior to use.
resistance information for sintered permanent magnets.
5.2 Although prediction of performance in natural environ-
2. Referenced Documents
ments has seldom been statistically correlated with corrosion
2.1 ASTM Standards:
test results, sufficient empirical results are available to support
D3330/D3330M TestMethodforPeelAdhesionofPressure-
the usefulness of this test in quantifying relative resistance to
Sensitive Tape
corrosion from moisture and heat.
2.2 JEDEC Standards:
5.3 The reproducibility of results in this test method is
JESD22-A102-C Accelerated Moisture Resistance – Unbi-
dependentonthetype,size,andshapeofspecimenstested,and
ased Autoclave
the control of the operating variables. In any testing program,
sufficient replicates should be included to establish confidence
3. Terminology
limits. Replicates may be run simultaneously, in subsequent
3.1 Definitions:
test runs, or in duplicate test chambers.
5.4 When multiple test chambers and operators are utilized,
efforts shall be made to perform a suitable repeatability and
This test method is under the jurisdiction of ASTM Committee A06 on
reproducibility study for the equipment, operators, and test
MagneticPropertiesandisthedirectresponsibilityofSubcommitteeA06.01onTest
method.
Methods.
Current edition approved May 1, 2011. Published May 2011. DOI:10.1520/
A1071_A1071M–11.
6. Interferences
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
6.1 This test method will not yield meaningful results if
Standards volume information, refer to the standard’s Document Summary page on
nonhomogeneous specimens such as assemblies or partially
the ASTM website.
coated magnets are tested because of the potential aggravating
Available from JEDEC Solid State Technology Association, 2500 Wilson
Boulevard, Arlington, VA 22201–3834. www.jedec.org effect of galvanic corrosion between dissimilar materials,
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A1071/A1071M − 11
chemical reactivity with included materials, incompletely ex- relief valve) shall be employed to ensure that the pressure
posed surfaces, and difficulty in determining the amount of within the equipment does not exceed its design limit.
weight loss attributable to the magnet and coating.
9.2 This test method utilizes pressurized steam which has
6.2 Many cleansers contain bleach or chlorides which will the ability to cause severe burns. Suitable means should be
increase the corrosion rate of the samples being tested. Do not employed to ensure that personnel are protected from vented
use bleach- or chloride-containing cleansers to clean the steam during operation, and in particular when the chamber is
interior of the test chamber or sample racks. Nonmetallic opened at the conclusion of the test.
scrubbing pads and water rinsing have been found to be
9.3 This test method utilizes elevated temperature. Suitable
suitable for routine cleaning of chambers and racks.
means should be employed to prevent burns caused by the
equipment, vented steam, and the specimens.
7. Apparatus
10. Sampling, Test Specimens, and Test Units
7.1 Autoclave—Aheatedpressurechambercapableofmain-
taining pressurized steam at controlled temperature. The tem-
10.1 A minimum of three replicates should be tested.
perature shall be maintained within 62°C of the selected
10.2 Whenever possible the samples should be unmagne-
temperature for the duration of the exposure. The atmosphere
tized. Magnetized samples may be demagnetized electro-
during test shall be saturated steam (100% RH). This can be
magnetically or thermally, provided the thermal process does
achieved by venting the chamber as it reaches operating
not damage the sample or significantly change its metallurgical
temperature and pressure and resealing the chamber after
state. Magnetized samples may be used in the magnetized state
pressure has been reduced to 5 psi [34 kPa] through venting.
provided they are secured on the rack so that they do not
The escaping steam purges the chamber of air, leaving only
contact other samples. Care shall be taken to prevent magnetic
steam within the chamber. While commercial autoclaves are
particles from being attracted to and sticking to the test
available that have self-contained heaters and timers, a con-
samples, causing erroneous readings. Obtaining accurate
ventional pressure cooker with external heater may also be
weights of magnetic material is difficult on many balances. For
used, as long as temperature and pressure controls capable of
magnetized samples, equipment and techniques that yield
maintaining suitable control of these variables are present.
accurate weights shall be used, including spacing the magnet
7.2 Balance—With suitable holders capable of measuring
away from the mechanism of the balance.
the mass of magnetic material to within 60.001 g or 60.1% of
11. Preparation of Apparatus
the magnet’s nominal weight (whichever is greater).
11.1 All equipment and specimen holders shall be inspected
7.3 Specimen Holders or Racks—Suitable containers or
and cleaned as necessary prior to use to ensure that the test
racks which can keep specimens from touching each other or
chamber, support racks, and other components are free of
metallic parts of the autoclave chamber. They must be con-
debris and visible contamination.
structed of material that will not affect the corrosion rate of the
sample. Suitable materials of construction have been found to
12. Calibration and Standardization
be aluminum (see Note 1), borosilicate or laboratory glass, or
12.1 Verify calibration of balance and autoclave (tempera-
halogen-free polymers.
ture controller). Verify that autoclave test temperature is
NOTE 1—Aluminum readily develops an insulating film when exposed
operating within specified range (see 7.1).
to air or steam. Care should be exercised when using freshly prepared or
refinished aluminum surfaces as the oxide film may be thin enough to
13. Sample Preparation
allow galvanic corrosion with the magnet under test. Generally, after
13.1 Test
...