ASTM C703-72(2021)

Standard Test Methods for Spalling Resistance of Porcelain Enameled Aluminum

SIGNIFICANCE AND USE
3.1 It is difficult to overemphasize the importance of the spall test. Porcelain enameled aluminum that fails this test will probably spall in service if subjected to moisture or weathering.
SCOPE
1.1 These test methods cover accelerated determination of the resistance of porcelain enamel coatings on aluminum alloys to spalling from exposure to moisture or weathering. Test Method A,2 using a 5 % solution of ammonium chloride, requires 96-h immersion while Test Method B,3 using a 1 % solution of antimony trichloride, is completed after 20 h of immersion. The spalling tendency is evaluated by the same criteria in both methods. While either method is suitable for magnesium silicon alloys, such as 6061, Test Method B is preferred for simple alloys or commercially pure aluminum, such as 1100.  
1.2 The test methods appear in the following order:    
Sections  
Test Method A—Ammonium Chloride  
4 – 9  
Test Method B—Antimony Trichloride  
10 – 15  
1.3 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

• Status: Published
• Publication Date: 31-Mar-2021
• ICS: 25.220.50 - Enamels
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.12 - Materials for Porcelain Enamel and Ceramic-Metal Systems

Overview

ASTM C703-72(2021) - Standard Test Methods for Spalling Resistance of Porcelain Enameled Aluminum - provides a comprehensive framework for evaluating the durability of porcelain enamel coatings on aluminum alloys. Developed by ASTM International, this standard defines methods to determine the resistance of these coatings to spalling, which is the separation or flaking of the enamel layer due to exposure to moisture or weathering. Ensuring spalling resistance is vital, as failures in this area can lead to premature degradation of enameled aluminum products, compromising their performance and lifespan in service environments.

Key Topics

• Spalling Resistance Assessment: The standard outlines accelerated test methods to measure how porcelain enamel coatings on aluminum withstand spalling under controlled exposures.
• Test Methods:
  • Test Method A uses a 5% ammonium chloride solution for a 96-hour immersion period.
  • Test Method B employs a 1% antimony trichloride solution for a 20-hour immersion period.
• Application to Alloys:
  • Both test methods are suitable for magnesium silicon aluminum alloys (such as 6061).
  • Test Method B is preferred for simpler alloys or commercially pure aluminum (e.g., 1100).
• Evaluation Criteria: Spalling is identified by visible separation of the enamel from the base metal, including specific guidelines for area and frequency of spalls that are classified as failures.
• Reporting Requirements: Detailed documentation on test results, specimen identification, and processing history is required for full transparency and traceability.

Applications

ASTM C703-72(2021) is essential for quality control and assurance in industries manufacturing or utilizing porcelain enameled aluminum components, including:

• Architectural Panels & Building Facades: Reliable coatings protect against weather-induced damage and extend material longevity.
• Consumer Appliances: Ensures durable, safe, and attractive finishes for aluminum cookware, home appliances, and fixtures.
• Transportation Components: Applies to enameled aluminum parts used in automotive, aerospace, and marine applications where environmental exposure is a concern.
• Industrial Equipment: Supports the quality verification process for enameled surfaces exposed to corrosive or humid settings.

By standardizing how spalling resistance is tested, ASTM C703-72(2021) helps manufacturers demonstrate product reliability, comply with international quality standards, and reduce the risk of field failures due to enamel coating defects.

Related Standards

• ASTM B921/B921M: Standard Specification for Nonporous Anodic Coatings on Aluminum and Aluminum Alloys
• ASTM B117: Standard Practice for Operating Salt Spray (Fog) Apparatus (for corrosion testing)
• ASTM C724: Standard Test Method for Acid Resistance of Porcelain Enamels
• ISO 28765: Vitreous and porcelain enamels - Production of specimens for testing
• ISO 2812: Paints and varnishes - Determination of resistance to liquids

Referencing related standards helps laboratories and manufacturers implement a comprehensive material testing and quality assurance program, supporting compliance with worldwide market requirements for enameled aluminum products.

Keywords: ASTM C703, spalling resistance, porcelain enameled aluminum, aluminum alloys, durability testing, quality control, accelerated weathering test, ammonium chloride test, antimony trichloride test, enamel coating durability, industrial standards.

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: C703 − 72 (Reapproved 2021)
Standard Test Methods for
Spalling Resistance of Porcelain Enameled Aluminum
This standard is issued under the fixed designation C703; 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, using an ammonium chloride or antimony trichloride test solution, covers an accelerated
procedure for determining the resistance of porcelain enamel coatings on aluminum and aluminum
alloys to spontaneous loss of adhesion (spalling) resulting from exposure to moisture, weathering, or
other environmental stress.
1. Scope apparent external cause. Spalling can result from the use of
improper alloys or enamel formulations, incorrect pretreatment
1.1 These test methods cover accelerated determination of
of the base metal, or faulty application and firing procedures.
theresistanceofporcelainenamelcoatingsonaluminumalloys
to spalling from exposure to moisture or weathering. Test
2 3. Significance and Use
Method A, using a 5 % solution of ammonium chloride,
requires 96-h immersion while Test Method B, using a 1 % 3.1 It is difficult to overemphasize the importance of the
solution of antimony trichloride, is completed after 20 h of spall test. Porcelain enameled aluminum that fails this test will
immersion. The spalling tendency is evaluated by the same probably spall in service if subjected to moisture or weather-
criteria in both methods. While either method is suitable for ing.
magnesium silicon alloys, such as 6061, Test Method B is
TEST METHOD A—AMMONIUM CHLORIDE
preferred for simple alloys or commercially pure aluminum,
such as 1100.
4. Apparatus
1.2 The test methods appear in the following order:
4.1 Container, glass or plastic, large enough to immerse the
Sections
test area of the specimen completely and hold a minimum of 3
Test MethodA—Ammonium Chloride 4–9
Test Method B—Antimony Trichloride 10–15 mL of solution per square centimetre of the immersed surface.
No metal other than the base metal of the specimen may be
1.3 This international standard was developed in accor-
exposed to the test solution.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
5. Reagent
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
5.1 Ammonium Chloride Solution (5 %)—The test solution,
Barriers to Trade (TBT) Committee.
freshly prepared, shall consist of 5 parts, by mass, of ammo-
nium chloride (NH Cl) (technical grade is adequate) dissolved
2. Terminology
in 95 parts, by mass, of water. Deionized or distilled water is
2.1 Definitions:
preferred, but in the case of very large production pieces, tap
2.1.1 spalling—a defect characterized by separation of the
water may be used. Sufficient solution shall be prepared to
porcelain enamel from the aluminum base metal without
permit complete immersion of the specimens.
These test methods are under the jurisdiction of ASTM Committee B08 on
6. Test Specimens
Metallic and Inorganic Coatings and are the direct responsibility of Subcommittee
6.1 Full-size production pieces should be tested. When this
B08.12 on Materials for Porcelain Enamel and Ceramic-Metal Systems.
Current edition approved April 1, 2021. Published May 2021. Originally
is not practical, specimens approximately 4 by 6 in. (102 by
approvedin1972.Lastpreviouseditionapprovedin2016asC703 – 72(2016).DOI:
152 mm), cut from production parts should be tested. At least
10.1520/C0703-72R21.
2 one representative specimen from each “job” or each 1000 ft
Method A is based on Bulletin AL-1a, Recommended Test Methods for
Evaluation and Control of Quality of Porcelain Enamel on Aluminum ,ofthe (93 m ) of production, whichever is applicable, should be spall
Porcelain Enamel Institute.
tested. Spall-tested pieces should not be shipped.
Method B is based on Bulletin T-51, Antimony Trichloride Spall Test of
Porcelain Enameled Aluminum, of the Porcelain Enamel Institute. 6.2 Test production parts in as-produced condition.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959. United States
C703 − 72 (2021)
7. Procedure tested. It is necessary that the metal-enamel interface is
exposed to the test solution. Cut edges or the cracks in the
7.1 Immerse the test specimens completely in the NH Cl
enamel caused by bending over a mandrel usually accomplish
solution at room temperature. Large production pieces may be
this. If not, the interface should be exposed by scoring the
immersed in a container made by lining a packing box with
enamel. At least one representative specimen from each “job”
polyethylene plastic sheeting.
2 2
or each 1000 ft (93 m ) of production, whichever is
7.2 Make a visual inspection after 96 h of immersion.
applicable, should be spall tested.
NOTE 1—Variations of this test may be used for studies of processing
12.2 Test production parts in as-produced condition.
variables.These include scored or deformed samples, 24 h inspection, and
multiple cycles of 96 h each.
12.3 Wherever practical (such as porcelain enameled sheet
material) specimens cut from production pieces should be bent
8. Evaluation
toa45°angleovera ⁄2-in.(12.7-m
...