Overview
EN ISO 18332:2008 (ISO 18332:2007) - Metallic and other inorganic coatings - Definitions and conventions concerning porosity - defines porosity-related terminology and sets out the principles for porosity testing of metallic and related inorganic coatings. The standard helps users select appropriate porosity tests for a given coating, substrate and service application, while clarifying that porosity tests cannot be used to establish corrosion-performance standards.
Key topics and requirements
- Definitions: clear terms for porosity, pore, discontinuity and corrosion product, enabling consistent communication across testing and specification documents.
- Purpose of porosity testing: determine coating quality and freedom from porosity, particularly on functional surfaces such as electrical contacts.
- Two principal test modes:
- Electrochemical tests - accelerated methods using an applied potential/current and an indicator in an electrolyte, gel or filter paper to reveal breaches in the coating by dissolution and migration of base‑metal ions. Ideal for process control and short exposure times.
- Exposure (environmental) tests - immersion, solution‑fog or gas‑atmosphere exposures that produce corrosion products at pore sites. Typically longer duration and suited to qualification testing.
- Principles and limitations: guidance on test selection based on coating, substrate and any undercoat; cautions on avoiding artefacts (e.g., anodic dissolution) and recognizing that exposure tests reflect mechanisms but are not direct measures of service performance.
- Rating and evaluation: specimen assessment after exposure should follow viewing conditions in the applicable product standard and may include:
- number of pores/discontinuities per unit area,
- percentage area covered by corrosion products/indications,
- area of the largest marking or corrosion spot.
- Test report content: must include at minimum the test type/specification, test conditions, details of articles tested, inspection conditions, rating, and any deviations from the product standard.
Applications and users
EN ISO 18332:2008 is useful for:
- coating manufacturers and process engineers (quality control and process optimization),
- corrosion engineers and materials specialists (test selection and interpretation),
- independent testing laboratories (methodology and reporting),
- product specifiers, OEMs and procurement teams (defining acceptance criteria and inspection requirements),
- standards writers and test-method developers.
Keywords: EN ISO 18332:2008, porosity testing, metallic coatings, inorganic coatings, porosity definitions, electrochemical tests, exposure tests.
Related standards
This standard provides foundational terminology and principles to help select and interpret porosity tests across manufacturing, quality assurance and qualification activities for metallic and inorganic coatings.