ASTM C536-83(1998)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: C 536 – 83 (Reapproved 1998)
Standard Test Method for
Continuity of Coatings in Glassed Steel Equipment by
Electrical Testing
This standard is issued under the fixed designation C 536; 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 4. Significance and Use
1.1 This test method covers the detection of discontinuities 4.1 This test method is designed to detect existing discon-
in the glass coating of glassed steel equipment where such tinuities in the glass coating of glassed steel equipment while
discontinuities would result in early failure due to the attack of maintaining a voltage low enough as to be unlikely to cause
the chemical contents of the vessel on the metal substrate. It is breakdown of the coating. The test is adaptable for manufac-
applicable to (1) provide a manufacturing and inspection test of turing inspection in the processing of equipment and for field
glassed-steel equipment designed for relatively mild, low- use to find existing defects which can be “plugged” or repaired
temperature corrosive service, and (2) the field testing of before serious damage is done to the equipment. As a means of
similar equipment used in more severely corrosive environ- positive detection, it is applicable to process studies, quality
ment. control, or specification.
NOTE 1—A manufacturing test method for the latter type of equipment
5. Definition
is described in Method C 537.
5.1 glassed steel (glass-lined steel or glass-coated steel)—
1.2 This standard does not purport to address all of the
designations generally applied to a class of porcelain enamels
safety concerns, if any, associated with its use. It is the
that have high resistance to chemical attack at elevated
responsibility of the user of this standard to establish appro-
temperatures and pressures.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. 6. Interferences
6.1 Since the test method is electrical, it is necessary to have
2. Referenced Document
a good ground connection between the instrument and the
2.1 ASTM Standards:
metal substrate of the equipment being tested. It is also
C 537 Test Method for Reliability of Glass Coatings on
necessary that the surfaces of the glass be reasonably clean and
Glassed Steel Reaction Equipment by High Voltage
dry. A wet surface will conduct enough voltage to any exposed
metal to give an indication of a “contact” over a large area
3. Summary of Test Method
instead of at a specific area of discontinuity. Such a capacitance
3.1 The test method consists essentially of grounding the
discharge can be distinguished from a true failure by extending
metal structure of the equipment being tested to the ground side
over a large area instead of at local spots that could be
of a voltage generator and sweeping the surface of the glass
identified and marked for repair.
with a suitable probe electrically connected to the other side of
the generator. Wherever a discontinuity exists, a discharge will
7. Apparatus
give a positive indication that such a discontinuity exists. The
7.1 The test apparatus comprises a voltage stabilizing trans-
voltage is set at 5000 V in order to show existing discontinui-
former, a step-up transformer, a current-limiting resistance, a
ties without breaking through the existing glass coating. A
voltmeter and pilot light, along with a suitably insulated cable
built-in current limiting device ensures electrical safety for the
and probe handle equipped with interchangeable wire brush-
operator.
type and point electrodes (see Fig. 1 for a schematic wiring
diagram). The current output is limited to 2.5 mA. The wire
This test method is under the jurisdiction of ASTM Committee B-8 on Metallic
and Inorganic Coatingsand is the direct responsibility of Subcommittee B08.12on
Materials for Porcelain Enamel and Ceramic-Metal Systems. When requesting information, specific reference should be made to the ASTM
Current edition approved Feb. 25, 1983. Published April 1983. Originally Designation number. Suitable test equipment is available from: Asso
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