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Q. What is a soluble salt tester?

A.   A soluble salt tester measures the quantity of soluble salts on a substrate, prior to painting. To do so, deionized water is placed against the substrate, allowing any soluble salts to dissolve into it. If soluble salts are present, they will increase the conductivity of the water, allowing electrical current to pass through easier. The greater the soluble salt contamination on the surface, the higher the conductivity of the water. This increase can be measured, and after some calculation (automatically performed by the PosiTector SST in accordance with ISO 8502-9), the concentration of soluble salts on the substrate can be established.

Q. Why is salt contamination measurement important?

A. The presence of soluble salts has been shown to have a significant negative effect on coating performance and leads to premature coating failure. Salts remaining beneath a protective coating create an osmotic force that draws water from the atmosphere through the paint layer. The pressure created by this water underneath the coating overcomes the adhesive bond between the coating and substrate, resulting in corrosion, osmotic blistering and eventual coating failure. It is therefore critical to ensure that a substrate is free from soluble salt contamination before painting.

Q. What is measured?

A. The PosiTector SST includes a certified and traceable conductivity probe specifically designed for ISO 8502-6,9. Included with each probe is a Long Form Certificate of Calibration. The following parameters are measured by the PosiTector SST:

  • Conductivity (µS/cm)
  • Sampling Temperature (C° or F°) normalized to 25°C
  • Test duration

Using the measured conductivity value and the sample test volume (set within the gage menu), the surface density of the salts (mg/m2 or µg/cm2) is automatically calculated in accordance with ISO 8502-9, saving the gage operator time and eliminating the chance of a calculation error.

Q. What are some typical applications?

A. The PosiTector SST is ideal for:

(a) testing substrates for the presence of soluble salts in accordance with ISO 8502-6,9 (the Bresle Method)

(b) testing blast media in accordance with ASTM 4940 and ISO 11127-6 (determination of water-soluble contaminates in abrasives by conductivity measurement)

(c) testing the conductivity of water within the range of 0-500 µS/cm

Q. What are the available options?

A. The PosiTector SST Soluble Salt Tester probe can be used with either the Standard or Advanced PosiTector gage body. In addition to the model feature differences, you have the choice among a variety of Bresle Method patch options.

Bresle Method Patch Options
Select from three Bresle Method patch options to suit your needs or use any commercially available patch.


DeFelsko Adhesive Patch

Latex Adhesive Patch



Q. Why choose one patch over another?

A. The PosiPatch is an improved version of commercially available Bresle Patches and is ideal for most users. It attaches to the substrate using a magnetic ring instead of adhesive for faster set-up and to eliminate cleanup. It contains an air-permeable membrane that automatically removes air from the patch while water is injected, simplifying the test. It also features a dull dispensing tip designed to mate with the port in the PosiPatch, instead of the sharp needles required for conventional patches. Finally, it is reusable, reducing the per-test cost.

For users who prefer the familiarity of conventional patches, or who are measuring on non-magnetic surfaces, the DeFelsko Patch is ideal. It is similar to conventional patches, and is intended for customers who prefer an adhesive patch. It features a low-tack adhesive, making it easy to remove with minimal residue. It is latex-free, and therefore significantly less expensive than conventional patches.

For users who require a patch with latex construction (which can expand to a 15 ml sample size), we offer the DeFelsko Latex Patch. It also features a low-tack adhesive that leaves minimal residue. Additionally, it features an easy-to-remove tab on the paper backing.


Q. Which Bresle Method Patch option is the most cost effective?

A. When the PosiPatch is reused, it offers the lowest per-test costs of any commercially available Bresle Method Patch. If performing a single test, Bresle Method DeFelsko Patch has one of the lowest per-test costs in the industry. The below tables compare the per-test costs of various options, using competitive prices found online.

If performing 10 tests, and reusing the PosiPatch:


Q. How is the PosiPatch reusable?

A. The innovative PosiPatch uses a magnetic ring to hold it against the surface, so no adhesive is required. This means that the PosiPatch isn’t destroyed when removed from the surface, unlike conventional patches. After rinsing with deionized water, the PosiPatch can be used again. Dispose of the PosiPatch after it becomes worn - typically after many tests.

While a reused patch may be slightly contaminated with salts from previous tests, in our experience this effect is minimal. This effect would cause a high or pessimistic reading. In many cases, it is only important to ensure that salt contamination levels are below a certain threshold or specification, so a slightly higher reading is no issue. In the event a reused patch yields a measurement that exceeds specifications, repeat the test with a new PosiPatch in an adjacent location, to determine whether the high reading was caused by the reused patch.


Q. How many times can the PosiPatch be reused?

A. One of the many innovative features of the PosiPatch is its ability to be reused multiple times by rinsing with DI water between tests. The PosiPatch can be used repeatedly until water begins to leak through the air‐permeable membrane or the seal against the substrate.

In our tests on freshly blasted steel with a typical 50‐100 micron (2‐ 4 mil) profile, PosiPatches were reused dozens of times with no noticeable wear or leakage. Patch life will vary depending on use‐ if dragged along the substrate, lifespan will be reduced.

We believe that 10 uses is a very conservative estimate of lifespan and still yields the lowest per‐test cost of any commercially available Bresle Method Patch.


Q. Can I purchase a new PosiTector SST probe for my existing PosiTector gage body?

A. Yes. PosiTector SST probes are compatible with all PosiTector Standard gage bodies with a color display, and PosiTector Advanced gage bodies with serial numbers greater than 730,000. You can simply update their existing PosiTector gage body by following step-by-step instructions at


Q. I already have a soluble salt testing kit but would like to try the innovative PosiPatch. Must I buy an entire kit?

A. No. For users who currently own a soluble salt testing kit but would like to use the PosiPatch, we offer the PosiPatch Starter kit. It includes everything needed to use the PosiPatch with a DeFelsko or competitive soluble salt testing kit. The PosiPatch Starter Kit includes two syringes, two dispensing tips, five PosiPatch patches and a magnetic ring.


Q. Does the DeFelsko Bresle Method PosiPatch solution work on curved surfaces?

A. Yes. The Bresle Method PosiPatch is ideal for measuring on flat surfaces and curved surfaces with a diameter greater than 100 cm (40 inches). Our Bresle Method DeFelsko Patches are available for measuring on smaller diameter surfaces.


Q. I really like the PosiPatch, but what if I occasionally have to measure on small radiuses?

A. Easy. Get a PosiPatch test kit and a package of Bresle Method adhesive patches – either the DeFelsko patch or the Latex patch. Each comes with a needle that attaches to our syringe. This economical solution gives you the greatest flexibility to test on any surface!


Q. Is the new PosiTector SST compatible with PosiSoft solutions?

A. Yes. The PosiTector SST is compatible with the new PosiSoft Desktop v4, and the PosiTector App for Apple and Android. It is not compatible with legacy desktop versions or the PosiTector SmartLink.


Q. How are PosiTector SST probes calibrated at DeFelsko?

A. Each PosiTector SST is calibrated against known conductivity standards traceable to a National Metrology Lab. A Long Form Certificate of Calibration containing actual measured values is included with every probe.


Q. What is the cost to recertify the PosiTector SST Soluble Salt Tester?

A. The cost to recertify the PosiTector SST is $95 and includes a Long Form Certificate of Calibration. Turn-around time is usually one day.


Q. How long is the warranty on the PosiTector SST probe?

A. DeFelsko Corporation’s standard 2 year warranty applies to both the PosiTector body and probe.


Q. Does the DeFelsko Bresle Method PosiPatch solution work on curved surfaces?

A. Yes. The Bresle Method PosiPatch is ideal for measuring on flat surfaces and curved surfaces using a Standard or Flexible magnetic ring.

The Standard Magnetic Ring is included in all PosiPatch Kits and is the first choice for flat surfaces and curved surfaces with diameters greater than 1 m (40 in.).


The Flexible Magnetic Ring is intended for pipes and other tight diameters, it allows the PosiPatch to form a tight, leak-free seal on inside and outside diameters greater than 10 cm (4 in.)


Minimum ID is 12 cm (4.5 in.)


Q. How is the PosiTector SST conductivity probe different than the conventional conductivity meters included with most other test kits?

A. The PosiTector SST conductivity probe is specifically designed for ISO 8502-6,9 and has a number of features not found in conventional conductivity meters including . . .

  • An onscreen user interface to walk users through the Bresle test method, simplifying the task
  • Tracking and reporting of test duration (the total time of contact between the solvent and substrate) as required by ISO 8502-6
  • Automatic calculation of surface density with adjustments for different patch volumes – works with ANY Bresle-type patch
  • Free software for viewing and reporting data
  • Long form certificate of calibration traceable to NIST included at no extra charge. A certificate also comes with the included conductivity standard (calibration solution).
  • Automatic 25°C temperature normalization
  • Sample temperature recording as required by ISO 8502-9
  • Purpose-built, 1 ml test cell is optimized for the range, resolution and test volume of the Bresle Method
  • Rugged, stainless steel electrodes – ideal for industrial environments
  • Two year warranty

Q. What information does the PosiTector SST save in its memory for each test?

A. The PosiTector SST saves all measured information for each test. All information is also reported in PosiSoft software.  

  • Date and time of test
  • Test duration (the total time of contact between the solvent and substrate)
  • Background sample conductivity (µS/cm)
  • Background sample temperature (°C or °F)
  • Final sample conductivity (µS/cm)
  • Final sample temperature (°C or °F)
  • Increase in conductivity between background and final sample (µS/cm)
  • Calculated surface density of soluble salts (mg NaCl/m2, mg CL/m2, µg NaCl/cm2, or µg Cl/cm2)


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