ISO 18332:2007

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.