ISO 8502-2:2017

Overview

ISO 8502-2:2017 specifies a laboratory method to determine water‑soluble chloride contamination on steel substrates prior to painting. The standard covers a practical swabbing/wash‑off procedure (applicable in the field or laboratory) and refers to several analytical techniques for measuring chloride in the collected wash‑water. ISO 8502-2 is part of the ISO 8500 series on surface cleanliness for paint performance and corrosion control.

Key topics and requirements

• Scope: Targets chloride‑containing salts that are readily soluble in water; applicable to bare and previously coated steel surfaces. It provides a wash‑off sampling technique and guidance on analytical options.
• Sampling procedure:
  • Mark a test area (example: ~25 000 mm² - e.g., 250 mm × 100 mm) and record the actual area.
  • Use ~45 ml of high‑purity water to soak absorbent pads and thoroughly swab the area; collect washings and filter into a 50 ml volumetric flask.
  • Swabbing should take at least 10 minutes and tests are carried out in duplicate.
• Analytical methods (selection referenced in the standard):
  • Ion chromatography (ISO 10304-1)
  • Ion detection tubes (ISO 8502-5)
  • Ion‑selective electrode (ISO 9517)
  • Coulometric titration (informative Annex A)
  • Conductivity conversion (ISO 8502-9) when non‑specific assessment is acceptable
• Result expression: Calculate chloride mass per area (mg/m²) from measured chloride concentration, sample volume and test area (formula provided in Clause 7). Account for any dilutions or conditioning steps.
• Limitations: Method measures only readily water‑soluble chloride removed by the wash; it does not represent total chloride trapped in crevices, pits or beneath corrosion films. Measurement uncertainty must be reported.
• Reporting: Test reports must identify the surface, method used, individual and mean results, deviations, anomalies and test dates.

Applications and users

ISO 8502-2 is used to assess surface cleanliness to reduce coating failure and corrosion risks. Typical use cases:

• Coating specifiers and engineers verifying pre‑treatment requirements for bridges, ships, offshore structures, storage tanks and industrial plants.
• Inspection and quality control teams performing acceptance tests before painting.
• Laboratory analysts selecting and validating chloride analysis methods.
• Contractors and maintenance teams monitoring cleaning effectiveness and compliance with coating system requirements.

Related standards

• ISO 8502-5 (ion detection tube field method)
• ISO 10304-1 (ion chromatography for anions)
• ISO 9517 (ion‑selective electrode method)
• ISO 8502-9 (conductivity conversion)
• ISO/TR 15235 (guidance on acceptable contamination levels)

Keywords: ISO 8502-2, chloride determination, surface cleanliness, steel substrates, wash-water analysis, pre-paint inspection, coating quality control, coulometric titration.