Overview
EN ISO 8502-2:2017 (ISO 8502-2:2017) specifies a laboratory method for the determination of water‑soluble chloride salts on cleaned steel surfaces. The procedure involves washing a defined surface area with a known volume of water, then analysing the wash solution by appropriate instrumental techniques. The standard applies to bare steel and previously coated surfaces and is intended to assess surface cleanliness prior to the application of paints and related protective coatings.
Key topics and requirements
- Scope and principle: Extraction of chloride-containing salts that are readily soluble in water by washing a defined test area; subsequent measurement of chloride concentration in the wash water.
- Sampling limitations: The method indicates surface contamination level but does not necessarily remove all salts (e.g., salts in crevices, pits or under films), so results are indicative rather than absolute.
- Reagents and apparatus: Requires analytical‑grade reagents, water meeting ISO 3696 Grade 3, marking materials, absorbent cotton pads (1–1.5 g), volumetric glassware and common lab items (pipettes, flasks, filters).
- Analytical methods referenced: A selection of chloride analysis techniques is referred to; a coulometric titration method is included in an informative annex (Annex A).
- Procedure essentials: Tests should be carried out at least in duplicate; results are reported as chloride concentration in the wash solution converted to amount of chloride per surface area.
- Precision considerations: Accuracy is limited by the chosen analysis method and sampling uncertainties; the standard notes potential interferences from corrosion layers, oils, or passivation films.
Practical applications and users
EN ISO 8502-2:2017 is used to:
- Verify pre‑painting surface cleanliness on structural steel, pipelines, ship hulls, bridges, and offshore assets.
- Support quality control and acceptance testing in surface preparation and coating contracts.
- Guide corrosion engineers, coating inspectors, laboratory technicians, paint manufacturers, and contractors in assessing risk of under‑film corrosion due to soluble chlorides.
- Complement field methods for soluble salts (e.g., ion detection tubes, Bresle patch) when laboratory analysis or confirmation is required.
Related standards
- ISO 8502 series (other parts cover field methods and different ions):
- Part 5 (field chloride detection), Part 6 (Bresle method for soluble contaminants), Part 9 (conductometric field method), Part 11 (turbidimetric sulfate), Part 12 (titrimetric ferrous ions).
- ISO 3696 (water for analytical laboratory use)
EN ISO 8502-2:2017 is essential for organizations requiring reliable laboratory assessment of chloride contamination as part of a comprehensive surface preparation and coating quality assurance program.
