Overview
EN ISO 8502-5:2025 - "Preparation of steel substrates before application of paints and related products - Tests for the assessment of surface cleanliness - Part 5: Measurement of chloride on steel surfaces prepared for painting (ion detection tube method)" - specifies a field test method for measuring chloride ions on steel surfaces using special ion detection tubes. The procedure applies to steel before and after cleaning and to painted surfaces between coat applications. It is a CEN-adopted ISO document intended for on-site chloride assessment as part of surface cleanliness and coating quality control.
Key topics and technical requirements
- Principle: Remove a proportion of water- or acid-soluble chlorides by controlled extraction (washing or immersion) and analyse the collected extract using a silver chromate-based ion detection tube; chloride presence is indicated by a colour change.
- Apparatus & materials:
- Chloride ion detection tube: borosilicate glass tube (140–150 mm length, 2–3 mm ID) containing ~5% silver chromate in silica sand (177–250 µm), retained by cotton plugs and glass powder; sealed ends.
- Extraction solvent: as specified in ISO 8502-2 (water), ISO 8502-6 (Bresle method), or ISO 8502-15 (acid extraction).
- Cutter, vessel and gloves for safe handling and sample presentation.
- Calibration & verification: Detection tubes must be calibrated against known chloride concentrations; verification tests and appropriate tube selection for the measurement range are required.
- Procedure and reporting: The standard covers extraction, determination of chloride concentration, expression of results, and required test-report content.
Practical applications
- On-site chloride screening during surface preparation and pre-paint inspections.
- Quality control for new coatings and maintenance painting to prevent underfilm corrosion caused by soluble chlorides.
- Fast verification of cleaning effectiveness after abrasive blasting, water jetting, or chemical cleaning.
- Integration into coating specification and acceptance criteria for structures exposed to marine or industrial environments.
Who should use this standard
- Coating inspectors and third‑party surveyors
- Surface‑preparation contractors and applicators
- Corrosion engineers and asset owners (bridges, offshore, industrial plants)
- Paint and coating manufacturers and specification writers
- Maintenance planners implementing ISO 12944-related corrosion protection strategies
Related standards
- ISO 8502-2 - Laboratory determination of chloride on cleaned surfaces
- ISO 8502-6 - Extraction of water‑soluble contaminants (Bresle method)
- ISO 8502-15 - Acid extraction of soluble contaminants
- ISO 12944-8 - Development of specifications for corrosion protection by paint systems
Keywords: EN ISO 8502-5:2025, chloride measurement, ion detection tube method, surface cleanliness, steel substrate preparation, Bresle method, paint inspection, coating quality control.
