Overview
ISO 18332:2007 - "Metallic and other inorganic coatings - Definitions and conventions concerning porosity" defines porosity-related terms and sets out the principles for porosity testing of metallic and other inorganic coatings. The standard helps users select appropriate porosity tests for a coating/substrate combination and its intended service, while clarifying that porosity testing is not a substitute for establishing corrosion-performance criteria.
Key topics and requirements
- Definitions and terminology
- Clear definitions of porosity, pore, and discontinuity as they relate to coatings and exposed substrate.
- Purpose of porosity testing
- Determines coating quality and absence of porosity, particularly where electrical contact or other functional requirements exist.
- Emphasizes that porosity tests identify presence, distribution and extent of pores but do not establish corrosion-performance standards.
- Two principal testing approaches
- Electrochemical tests: accelerated techniques that use the coating/substrate as an anode in a cell, with an inert cathode and an indicator in an electrolyte or conductive gel/paper to visualise ion migration and pore locations.
- Exposure (chemical) tests: longer-term immersion, vapor or atmospheric exposure that promotes corrosion-product formation at pore sites, enabling visual or chemical development of pore indications.
- Evaluation and rating
- Specimens are assessed after exposure under specified observation conditions. Typical reporting elements include:
- number of pores/discontinuities per unit area,
- percentage area covered by corrosion products or pore indications,
- largest marked area or most extensive corrosion location.
- Test reporting requirements
- Minimum report items: test type/specification, test conditions, specimen details, inspection conditions, rating, and any deviations from product standards.
Applications and users
ISO 18332 is practical for:
- Coating manufacturers and formulators assessing coating integrity and quality control.
- Quality engineers and inspection laboratories selecting appropriate porosity tests.
- Corrosion engineers and materials specifiers choosing tests based on substrate, coating type and service environment.
- Procurement and product engineers who need to specify porosity inspection requirements on drawings and product standards.
Practical value: helps match test method (accelerated electrochemical vs long-term exposure) to product qualification, process control and functional requirements while providing consistent terminology and reporting guidance.
Related standards
- ISO 10308 (porosity test review and classification)
- ISO 2080 (vocabulary for electrolytic deposits)
- ISO 8044 (corrosion terms)
- ISO 10289 (corrosion test specimen rating)
- EN 12508 (surface treatment and coatings vocabulary)
Keywords: ISO 18332, porosity testing, metallic coatings, inorganic coatings, pore definition, electrochemical tests, exposure tests, coating quality, porosity assessment.
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