Practical Guide
Using Elcometer 138/2 Correctlly: Reliably detect surface contamination (Bresle) – in 10–15 minutes
Invisible salts, chloride, iron, or pH deviations are common causes of early coating failure. This guide shows you the field-proven workflow with the Elcometer 138/2 – including guide values, error checks, and maintenance routines.
Product Overview: What does the Elcometer 138/2 measure – and why?
The Elcometer 138/2 is a surface contamination test kit that checks for invisible contaminants – specifically pH value, chloride ions, iron, and salts. The goal: prevent coating defects before they become expensive.
| Area | How does it work? | Typical Benefit |
|---|---|---|
| Bresle Probe (ISO 8502-6) | Deionized water is circulated in the Bresle sampler over a defined area, then the solution is tested. | Reproducible sampling instead of "gut feeling." |
| Chloride | Capillary Titrator (Quantab): wait for saturation, read the scale, and convert to ppm/mg/L via table. | Detect corrosion risk under the coating early. |
| Iron | Dip the test strip briefly, observe reaction time, compare with color scale. | Make rust/iron residues visible after blasting/grinding. |
| pH | Dip the test strip, compare colors; for weak solutions, dip longer if necessary (guide value). | Identify chemical deviations that can impair adhesion/durability. |
Bresle Test Area
12.5 cm²
Constant area for comparable results.
Sample Volume (Bresle)
2.6 ± 0.6 ml
Crucial for comparability & conversion.
Chloride Measuring Range
30–600 ppm
As Cl⁻ in the solution; conversion to surface area possible.
Pro Tip:
Wear clean latex or nitrile gloves during the entire process. The tests are very sensitive – even small contaminants from hand sweat or dirty beakers/syringes will distort the result. Rinse beakers, syringe, and needle with deionized water (not tap water) if necessary.
Recommended Basic Settings (Guide values from manual)
The following values are practical guidelines derived from the manufacturer's manual. Specifications/project standards always take precedence.
- Deionized Water: Draw approx. 3 ml into the syringe (discard remaining water in the beaker – do not pour back into the bottle).
- Injection into Sampler: Inject approx. 1.5 ml first, evacuate air from the sampler, then inject the rest (guide value).
- Exposure Time: On non-pitted, blasted surfaces, approx. 10 minutes is described as sufficient (guide value, surface dependent).
- Circulation Cycles: At least 4x "withdraw + re-inject" (guide value).
- Important Rule: If solution is lost during sampling, the test must be discarded and repeated.
Professional Workflow (5–7 Steps) – How to get reliable results
- Preparation: Put on gloves, keep beaker/syringe/needle clean, rinse with deionized water if necessary.
- Apply Bresle Sampler: Remove protective film, press sampler firmly onto the surface (ensure airtight seal!).
- Dose Water: Draw approx. 3 ml of deionized water into the syringe; discard remaining water in the beaker (do not return to bottle).
- Fill & Vent: Inject partial amount first, withdraw/remove air from sampler, then inject remaining amount.
- Expose & Circulate: After suitable time, withdraw solution and immediately re-inject; perform at least four cycles.
- Remove Solution: Finally, withdraw as much solution as possible, transfer to the beaker, and test immediately (Chloride/Iron/pH).
- Document & Clean: Record surface temperature, remove sampler, clean surface; rinse kit components with fresh water.
Understanding Measurement Logic: Converting ppm to "Salt per Area" (Guide value)
For chloride, the titrator typically provides a concentration in ppm (mg/L). The manual provides an estimate of the salt amount per area (based on a 3 ml sample from 12.5 cm²):
Guide Formula 1
µg/cm² = 0.4 × Concentration (ppm)
Guide Formula 2
mg/m² = 4.0 × Concentration (ppm)
Note: This conversion is an estimation "as sodium chloride" according to the manual (guide value/simplified model).
Troubleshooting: 4 typical problems – and what you can do immediately
1) Solution Lost / Leakage
- Discard test and repeat (manufacturer instruction).
- Press sampler edge firmly all around, check seal, only guide needle through the foam edge.
2) Air Bubble in Sampler
- Change needle position in sampler and evacuate air (standard procedure guide).
- Hold syringe with needle pointing up and expel air from the syringe.
3) Iron Test shows "Too High"
- If ≥ darkest scale value: Dilute sample with deionized water and measure again.
- Multiply the result by the dilution factor afterwards.
4) Color Change/Reading "Seems Odd"
- Iron: Observe 10s reaction time – do not count later color changes as measurement values.
- pH: For weak solutions, dip longer if necessary (until color change is stable; guide value).
Maintenance & Handling: Keeping the kit reliable
- Rinse components with fresh water after testing and reuse.
- Check test strips for expiration date before use; replace if exceeded.
- Keep beaker, syringe, and needle clean; rinse with deionized water if needed.
- Dispose of used (blunt) needles safely (note risk of injury).
- Store everything in the transport case when the kit is not in use.
Quick access to the right set (incl. Bresle Sampler & Test Strips)
The scope of delivery includes pH test strips, iron test strips, chloride test strips, Bresle samplers, syringes, needles, beakers, and a transport case.
FAQ (Field Oriented)
1) Which standard covers the sampling?
Sampling is carried out using the Bresle method in accordance with ISO 8502-6 (as described in the manual).
2) Why do I have to wear gloves?
Because the tests are very sensitive: even the slightest contamination can affect the sample or the surface.
3) How quickly must I measure after sampling?
Test immediately after transferring the solution to the beaker to avoid falsifications due to standing time/environment (best practice from the manual workflow).
4) What does "ppm" mean for chloride – and how do I compare area values?
ppm describes the concentration in the solution. For a surface estimation, the manual provides conversions (µg/cm² or mg/m²) as guide values.
5) What measuring ranges can the kit cover?
pH 0–14; Iron via scale steps up to 500 mg/l Fe²⁺; Chloride in the range of 30–600 ppm (depending on test strip/titrator).
Conclusion
With the Elcometer 138/2, you get a clearly structured Bresle workflow to quickly check invisible contaminants (pH, chloride, iron, salts) before coating. If you work cleanly (sealing, venting, no loss of solution, adhering to reaction times), you will receive reliable guide values for approval or post-cleaning – and significantly reduce the risk of expensive complaints.
