Choose a sampling plan that represents the tank’s exposure and preparation history. Include suspected salt sources and representative clean areas. A sample from one easy flat panel cannot establish the whole tank condition. [1]
Map locations before taking the result
| Location | Reason to include it | Record |
|---|---|---|
| Lower panel or drain area | Possible retained contamination | Exact area and orientation |
| Weld/attachment region | Preparation and accessibility differ | Method limitations on geometry |
| Exposed handled surface | Potential contamination after blasting | Time and handling history |
| Representative flat panel | Comparison with routine preparation | Substrate state and sample area |
Keep the measurement’s chemistry visible
Conductivity-based extraction can estimate soluble contamination under the method’s assumptions, but it does not uniquely identify every ion. If chloride or another specific ion is the concern, use appropriate ion-specific evidence rather than relabelling total conductivity as a chloride result.
Retain extraction area, liquid quantity, blank, temperature and method. In a component mass calculation, recovered mass divided by sampled area gives surface loading; incomplete extraction and conversion assumptions affect its meaning.
Conductometric determination concerns extracted water-soluble salts; it is not an ion-specific chloride measurement. [2]
Recalculate an extraction on its sampled area
Assumptions: a validated extraction recovers 0.10 mg of soluble contamination from 0.010 m², its matched blank is 0.02 mg, and the project method specifies a maximum blank-corrected recovered loading of 6 mg/m². The result is (0.10 − 0.02)/0.010 = 8 mg/m², exceeding that criterion by 2 mg/m²: reclean and resample the affected region. This criterion uses the recovered-method result, not an unverified total surface inventory. Preserve recovery, temperature and uncertainty; do not relabel conductometric contamination as chloride. [2]
References
- ISO, ISO 8502-6:2020, Preparation of steel substrates before application of paints and related products — Tests for the assessment of surface cleanliness — Part 6: Extraction of water soluble contaminants for analysis (Bresle method).
- ISO, ISO 8502-9:2020, Preparation of steel substrates before application of paints and related products — Tests for the assessment of surface cleanliness — Part 9: Field method for the conductometric determination of water-soluble salts.