Overview
ISO 28764:2015 is an international standard published by the International Organization for Standardization (ISO) that specifies a precise method for producing test specimens coated with vitreous and porcelain enamels on sheet steel, sheet aluminium, and cast iron substrates. This standard is critical for ensuring consistent and reliable testing of enamel coatings, particularly for assessing durability, adhesion, and mass loss under various conditions.
The document distinguishes between two types of specimens: those taken directly from production articles and specially produced specimens. Notably, specially produced specimens are required for quantitative measurements of enamel coating loss due to their higher accuracy compared to specimens cut from finished enamelled articles.
Key Topics
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Specimen Types and Designation
- Specimens may be cut from production articles or specially fabricated.
- Specially produced specimens are mandatory for quantitative loss of mass testing.
- Specimens are designated based on the substrate used: steel (A), cast iron (B), aluminium (C).
- Example Designation: Specimen ISO 28764-A for steel substrates.
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Specimen Dimensions and Shape
- Specimens should be flat, circular or square, with dimensions around 105 mm ± 5 mm.
- Holes for hanging during weighing or enamelling are optional but specified if needed.
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Substrate Requirements
- Steel substrates must be enamelling-quality sheet steel, typically thickness 0.3 mm to 3.0 mm.
- Cast iron substrates require enamelling-quality cast iron plates or bars, minimum thickness 2.5 mm.
- Aluminium substrates should be 2 mm to 3 mm thick aluminium alloys compliant with specific standards (e.g., EN AW-1050A).
- Conditioning treatments of substrates must be consistent for comparative purposes.
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Enamelling Procedures
- Enamelling follows the normal production process without additional steps like repair enamelling.
- The enamel thickness reflects production article standards to maintain comparability.
- Steel substrates may be coated on one or both sides depending on test requirements.
- Cast iron and aluminium have defined enamelling practices, including ground coat and cover coat applications.
- Edge enamel thickness should be minimized for accuracy.
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Specimen Surface Quality and Defect Inspection
- Visual inspections ensure test specimens are free from defects such as blisters, chipping, cracking, fish-scales, and spalling.
- For chemical industry applications, high-voltage testing (as per ISO 2746) is required to detect pinholes and weak areas.
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Safety Warning
- The standard includes safety warnings about handling substances and procedures that may pose health risks, underlining the responsibility of users to follow safety regulations.
Applications
ISO 28764:2015 is essential for manufacturers and laboratories involved in the enamel coating industry, including:
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Quality Control Laboratories
- Producing standardized specimens for routine testing of veneer enamel coatings on steel, aluminium, or cast iron parts.
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Research and Development
- Evaluating new enamel formulations or substrate materials under controlled conditions to optimize performance.
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Industrial Enamelling Facilities
- Ensuring production consistency by verifying enamel adhesion, thickness, and defect detection using properly prepared test specimens.
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Chemical and Container Manufacturing
- Applying stringent enamel testing for chemical-resistant containers and apparatus where coating integrity is critical.
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Regulatory and Certification Bodies
- Adopting a harmonized method for specimen preparation to ensure uniform enamel testing results worldwide.
Related Standards
- ISO 2746: Vitreous and porcelain enamels - High voltage test - A method referenced by ISO 28764 for detecting defects such as pinholes in enamel coatings.
- ISO 13805: Vitreous and porcelain enamels for aluminium - Determination of adhesion under electrolytic solution - Related to adhesion tests on aluminium-enamel specimens.
- EN 10209: Cold rolled low carbon steel flat products for vitreous enamelling - Technical delivery conditions, relevant for steel substrate specifications.
- EN 573-3: Aluminium and aluminium alloys - Chemical composition and form of wrought products - Defines aluminium alloys suitable for enamelling substrates.
Keywords: ISO 28764:2015, vitreous enamel, porcelain enamel, specimen production, enamel testing, enamel coatings, sheet steel, sheet aluminium, cast iron, enamel adhesion, enamel mass loss, enamel defect inspection, enamel substrate preparation, enamel quality control, industrial enamelling standards.
Open preview (PDF)Vitreous and porcelain enamels — Production of specimens for testing enamels on sheet steel, sheet aluminium and cast iron