ASTM C537-87(2023)

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: C537 − 87 (Reapproved 2023)
Standard Test Method for
Reliability of Glass Coatings on Glassed Steel Reaction
Equipment by High Voltage
This standard is issued under the fixed designation C537; 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.
INTRODUCTION
This test method covers the determination of the reliability of glass coating on metal using high
voltage. It is intended for use by manufacturers of equipment that is designed to withstand highly
corrosive conditions where a failure of the coating in service would cause extreme damage to the
exposed metal. The test method detects not only existing discontinuities in the glass coating, but also
areas where the glass coating may be thin enough to be likely to result in premature failure in service.
1. Scope 2. Terminology
1.1 This test method covers the determination of the reli- 2.1 Definitions:
ability of glass coating on metal and is intended for use by 2.1.1 glassed steel, glass-lined steel, or glass-coated steel,
manufacturers of equipment that is designed to withstand n—designations generally applied to a class of porcelain
highly corrosive conditions where a failure of the coating in enamels that have high resistance to chemical attack at elevated
service would cause extreme damage to the exposed metal. Its temperatures and pressures.
use outside the manufacturer’s plant is discouraged because
improper or indiscriminate testing can cause punctures that are 3. Summary of Test Method
difficult to repair without returning the equipment to the
3.1 This test method consists essentially of grounding the
manufacturer’s plant. This test method detects not only exist-
metal structure of the equipment to the ground side of a
ing discontinuities in the glass coating, but also areas where the
direct-current high-voltage generator and sweeping the glass
glass may be thin enough to be likely to result in premature
surface with a high-potential probe on the end of an insulated
failure in service.
handle and cable. Wherever a discontinuity exists or the
1.2 The values stated in SI units are to be regarded as coating is thin enough (by reason of a concealed bubble or
conducting inclusion, etc.) so that the dielectric strength of the
standard. No other units of measurement are included in this
standard. remaining glass is less than some preset desired amount, the
dielectric strength of air-plus-remaining-glass breaks down and
1.3 This standard does not purport to address all of the
a discharge occurs. Built-in current-limiting devices ensure
safety concerns, if any, associated with its use. It is the
electrical safety to the operator. A variable voltage control
responsibility of the user of this standard to establish appro-
allows selection of a voltage which assures a predetermined
priate safety, health, and environmental practices and deter-
minimum thickness of glass.
mine the applicability of regulatory limitations prior to use.
For specific precautionary statements, see Section 7.
4. Significance and Use
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard- 4.1 The widespread use of glassed-steel equipment in highly
ization established in the Decision on Principles for the
corrosive chemical processes has made it necessary to detect
Development of International Standards, Guides and Recom- weak spots in the coating and repair them before catastrophic
mendations issued by the World Trade Organization Technical
failure occurs in service. This test is intended to detect
Barriers to Trade (TBT) Committee. discontinuities and thin areas in a glass coating on metal to
ensure that the coating is defect free and has sufficient
thickness to withstand the prescribed service conditions. A test
This test method is under the jurisdiction of ASTM Committee B08 on Metallic
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.12 on
voltage may be selected at any desired value up to 20k V, thus
Materials for Porcelain Enamel and Ceramic-Metal Systems.
making the test applicable to a wide range of thickness
Current edition approved May 1, 2023. Published June 2023. Originally
requirements. When, because of bubbles or defects, the thick-
approved in 1964. Last previous edition approved in 2018 as C537 – 87 (2018).
DOI: 10.1520/C0537-87R23. ness of glass at any spot is less than enough to withstand the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C537 − 87 (2023)
FIG. 1 Circuit Diagram, 20k V dc Tester
applied voltage, a puncture results with an accompanying sweeping larger surfaces of glass coating while the point probe
indication of a defect. Remedial action is then required to
is better adapted to interior corners and the more restricted
repair the defect before the equipment can be used for
areas.
corrosive service. (When such defects are found before the
equipment leaves the manufacturer’s plant another application
7. Safety Precautions
of glass can usually be applied and fired to become an integral
7.1 The instrument and equipment being tested should be
part of the coating.)
well grounded both to a good ground and to each other. All
grounding contacts should be clean bare metal and not rusted
5. Interferences
or painted metal.
5.1 Since the test method is electrical, it is necessary to have
a good ground connection between the instrument and the 7.2 Handle the insulated probe handle so that the hand
metal substrate of the equipment being tested. It is also
contacts the ground ring to prevent build-up of a static charge
necessary that the surface of the glass be reasonably clean and which causes an unpleasant (although not dangerous) sensation
dry. A wet surface will conduct enough of the high voltage to
on discharge.
any exposed metal, including the edges of the glass coating, so
7.3 Keep the probe electrode at least 305 mm (12 in.) away
that an indication of a “contact” may be obtained over a large
from condu
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