ISO 8502-9:2020

Overview

ISO 8502-9:2020 specifies a field method for conductometric determination of water‑soluble salts on steel surfaces prior to painting. The standard uses an adhesive extraction cell (as in the Bresle method, ISO 8502-6) and a conductometer to assess the total surface density of soluble ionic contaminants (reported as total soluble salts). It is a rapid, on‑site test for salts that form electrolytes in water - the majority of corrosion‑promoting contaminants - but it does not identify individual ions (e.g., chloride, sulphate, sodium).

Key topics and technical requirements

• Principle: dissolve salts from a defined surface area with water in an adhesive cell, measure solution conductivity, and calculate total soluble salts using the method’s empirical conversion.
• Sampling: uses adhesive cells and sampling procedures referenced in ISO 8502-6 (Bresle patch). Record sampling area and volumes.
• Instrumentation:
  • Conductometer with temperature compensation to 25 °C.
  • Specified conductivity ranges and resolutions (e.g., 0–20 mS/m (0–200 µS/cm) at 0.01 mS/m resolution and 20–200 mS/m at 0.1 mS/m; accuracy ~2%).
  • Beaker and syringe (if used) for sample handling.
• Water quality: solvent water of at least ISO 3696 grade 3 (typically < 0.5 mS/m or < 5 µS/cm).
• Procedure essentials: instrument calibration (daily or before each test sequence), blank tests (syringe/beaker/electrode/water), extraction per ISO 8502-6, conductometric measurement, and calculation of corrected volume and surface salt density.
• Limitations: gives a total soluble‑salt value only; not ion‑specific; may not remove salts embedded in deep rust pits - extended or repeated extraction can increase recovery.

Applications

• Pre‑coating quality control: verify surface cleanliness before application of protective coatings.
• Maintenance and inspection: on‑site assessment for bridges, ships, pipelines, offshore structures, and industrial plants.
• Contractor and client acceptance testing: compliance checks where limiting soluble salts is specified in coating or project specifications.
• Research and troubleshooting: diagnosing adhesion failures, blistering, or premature corrosion linked to soluble contaminants.

Who uses this standard

• Coating inspectors and specifiers
• Surface‑preparation and blasting contractors
• Paint and coating manufacturers
• Asset owners and maintenance engineers
• Third‑party quality assurance laboratories

Related standards

• ISO 8502-6 (Bresle method - adhesive cell extraction)
• ISO 3696 (water for analytical laboratory use)
• ISO 8501, ISO 8503, ISO 8504 (surface cleanliness, roughness, and preparation methods)

Keywords: ISO 8502-9, conductometric determination, water-soluble salts, Bresle method, surface cleanliness, steel substrates, conductometer, pre-paint inspection.