How to measure salt contamination with the PosiTector SST Soluble Salt Tester by DeFelsko—the measure of quality.
Before the application of protective coatings, steel substrates must be thoroughly cleaned. The surface should then be tested to determine if there are excessive levels of salt contamination.
Soluble salts are not visible to the naked eye. If allowed to remain on the substrate in sufficient quantities, they can draw moisture through the coating causing premature coating failure from osmotic blistering or disbondment.
Put simply, the Bresle method involves placing a volume of water in a chamber against the surface. This water dissolves any soluble salts, raising the conductivity of the water. The measured increase in conductivity is related to the concentration of soluble salts on the surface.
The PosiTector SST guides users through the three simple steps required to take a conductivity measurement. It features a purpose-built test cell, optimized for the range, resolution, and test volume of the Bresle Method. A built-in temperature sensor compensates for accuracy and records the sample temperature for each measurement.
The PosiTector SST probe is factory calibrated and comes with a Long Form Certificate of Calibration traceable to NIST.
The PosiTector SST Soluble Salt Tester conductivity probe, when used in conjunction with either the Bresle Method PosiPatch, Bresle Method DeFelsko Adhesive Patch, or Latex Adhesive Patch simplifies the process of measuring soluble salt contamination. Like all DeFelsko products, each kit contains everything you need to start measuring.
Conventional Bresle Method patches consist of an adhesive foam ring with a plastic or latex sheet on one side. The DeFelsko Adhesive Patch is low cost, latex-free, and works on nearly any surface geometry.
It features a low-tack adhesive, which creates a tight seal while remaining easy to remove without leaving behind any foam residue. The DeFelsko Latex Adhesive Patch features tabs for easy removal and a TearGuard layer to prevent adhesive from being left on the surface.
The revolutionary DeFelsko PosiPatch further simplifies the Bresle method. It is functionally equivalent to traditional Bresle Patches, but requires no adhesive, as it is held against the surface by a rigid or flexible magnetic holding ring. It has a built-in port which allows fluid to be injected using a dull polypropylene dispensing tube, eliminating sharp needles from the test.
It features a patented air-permeable membrane, which automatically releases trapped air as water is injected, then agitates the water as it is withdrawn. It is also reusable, and a single PosiPatch can be used repeatedly until worn. Just rinse the test chamber with deionized water between uses.
To perform a Bresle Method test, first pour at least 4 milliliters of deionized water into a clean cup to prevent contamination of the water source.
Fill the syringe with deionized water from the cup. The PosiTector SST automatically displays the previous background measurement. Press the minus button to use it, or to take a new one, fill the Test Cell and once stabilized, press the plus button to save the new background measurement.
Draw water back into the syringe, removing all of the solution from the test cell. Invert the syringe and expel the air and excess solution until there are 3 milliliters of solution remaining in the syringe.
If using a traditional Bresle method patch, remove the backing and foam center from the patch, taking care not to touch the interior. Press it firmly onto the surface making sure most of the air escapes.
Using the syringe and a hypodermic needle, pierce the patch at the foam perimeter, allowing the needle to penetrate the center of the patch. Inject roughly half of the water into the patch. Then, use the needle to withdraw the air from the patch.
Remove the syringe from the patch and expel the air, then inject the rest of the water into the patch.
If using the PosiPatch, begin by placing it into the magnetic ring, ensuring the arrows align with the injection port. Take care not to touch the interior.
Place it onto the surface and inject the water into the patch using the injection port. The air within the patch automatically escapes through the air-permeable membrane.
Once the water is injected into either patch, press the plus Button to start the timer.
Use the syringe to repeatedly inject and withdraw the water, washing the surface. ISO 8502-6 recommends this process be repeated at least four times. The test time should be agreed upon between the interested parties. DeFelsko recommends a 2-minute test time.
After the desired amount of time has elapsed, withdraw the water from the test patch.
To complete the measurement, inject the water into the test cell of the PosiTector SST, allow the reading to stabilize, and press the plus button.
The PosiTector SST Soluble Salt Tester displays and saves all required information for each test including . . .
Press the plus button again to begin a new test. All results are stored in memory if a batch is open.
The patch can now be removed from the surface. The Bresle Method DeFelsko Patch peels off the surface easier and with less residue than conventional Bresle patches. It is disposed of after the test.
If using the reusable magnetic PosiPatch, remove it from the surface and rinse the test chamber with DI water. It is now ready for reuse.
Once a reading is saved into the PosiTector memory, PosiSoft Software can manage data and create professional reports.
The Bresle method has been used around the world for decades to measure salt contamination. Using these simple steps, inspectors can ensure that surfaces are free of excessive salt levels prior to painting.
The PosiTector SST Soluble Salt Tester makes the process of salt contamination measurement and reporting faster, simpler, and more accurate. The DeFelsko Adhesive Patch, Latex Patch, and innovative and reusable PosiPatch are ideal solutions for measuring salt contamination in accordance with ISO 8502-6/9—the Bresle method.
Visit DeFelsko.com/SST to learn more.