Check Powder thickness with Powder Comb before curing to help ensure correctly cured film thickness the first time through the line. Avoid stripping and re-coating which can cause problems with adhesion and coating integrity.
1. Push the Powder Comb perpendicularly into the dry powder so that the two stand-offs (end tabs) on both sides of the teeth rest firmly on the substrate.
2. Drag the Powder Comb along the surface of the coated part for at least 1 centimeter.
3. Remove the Powder Comb from the surface and examine the marks left in the powder.The powder thickness is between the highest numbered tooth which made a mark and has powder clinging to it, and the next highest tooth which left no mark and has no powder clinging to it.
Example: The 75 and 150 micron teeth both make lines and have powder clinging to them but the 225 mil tooth does not. The uncured powder thickness is determined to be between 150 and 225 microns. (see above image)
Note - Most powders cure to approximately 50% of their dry thickness. Marks left by the gage may affect the characteristics of the cured film.
Model 1 (mils)
Model 2 (mils)
Model 3 (mils)
Model 4 (μm)
Model 5 (μm)
Model 6 (μm)
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Stated accuracy of Td is ±3C for Td from -40 to 80C.
The following charts illustrate the maximum error of Td with respect to Ta and RH.
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.
The PosiPatch can be reused multiple times 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. The below tables compare the per-test costs of various options, using competitive prices found online.
If performing 10 tests, and reusing the PosiPatch:
Annotate images using drawing tools—ideal for identifying a specific location or area within an image
Unequal pulling force during testing caused by uneven adhesive bond lines and coating surfaces can result in random, unexplainable readings. To obtain more repeatable and meaningful adhesion measurements, it is imperative that the pulling force applied to the test dolly is uniformly distributed over the surface being tested.
Both the PosiTest AT-M manual and PosiTest AT-A automatic models compensate for misalignment. The self-aligning, quick-coupling actuator and spherical articulating dolly head enable uniform distribution of the pulling force over the surface being tested, preventing a one-sided pull-off.
Two grades of Testex™ Press-O-Film™ replica tape, “Coarse” and "X-Coarse", are available to span the primary range of surface profiles for the coatings and linings industry –– 20 to 115 µm / 0.8 to 4.5 mils.
An unfortunate characteristic of replica tape is that conventional spring micrometer measurements are most accurate near the middle of each grade's range and least accurate at the outer ends of each grade's range. That is why two other grades, Coarse Minus (< 20 µm / 0.8 mils) and X-Coarse Plus (> 115 µm / 4.5 mils), are used to check and, if necessary, adjust measurements at the upper and lower ends of the primary range.
Inside the primary range, Coarse and X-Coarse tape share a 38 - 64 μm (1.5 - 2.5 mils) "overlap" region. Measurements with conventional micrometers require a complicated and time consuming procedure of averaging one reading using Coarse grade and one reading using X-Coarse grade to achieve reasonable accuracy.
With a single measurement, the PosiTector RTR produces a more accurate peak-to-valley height measurement HL from Coarse or X-Coarse tapes that has been adjusted for their non-linearity. There is no need to average two or more replicas from different grades of tape AND there is no need to subtract the 50.8 μm / 2 mils of incompressible polyester film. The advantages are a reduction in measurement uncertainty, inspector workload, likelihood of error, and the number of replicas needed by inspectors to assure accuracy.
The PosiTector RTR can also display a height value (H) that is comparable to what conventional analog spring micrometers would display after the 50.8 μm / 2 mils of incompressible polyester film has been subtracted.
Eddy current techniques are used to nondestructively measure the thickness of nonconductive coatings on nonferrous metal substrates. A coil of fine wire conducting a high-frequency alternating current (above 1 MHz) is used to set up an alternating magnetic field at the surface of the instrument's probe. When the probe is brought near a conductive surface, the alternating magnetic field will set up eddy currents on the surface. The substrate characteristics and the distance of the probe from the substrate (the coating thickness) affect the magnitude of the eddy currents. The eddy currents create their own opposing electromagnetic field that can be sensed by the exciting coil or by a second, adjacent coil.
Magnetic film gages are used to non-destructively measure the thickness of a nonmagnetic coating on ferrous substrates. Most coatings on steel and iron are measured this way. Magnetic gages use one of two principles of operation: magnetic pull-off or magnetic/electromagnetic induction.
Magnetic pull-off gages use a permanent magnet, a calibrated spring, and a graduated scale. The attraction between the magnet and magnetic steel pulls the two together. As the coating thickness separating the two increases, it becomes easier to pull the magnet away. Coating thickness is determined by measuring this pull-off force. Thinner coatings will have stronger magnetic attraction while thicker films will have comparatively less magnetic attraction. Testing with magnetic gages is sensitive to surface roughness, curvature, substrate thickness, and the make up of the metal alloy.
Magnetic induction instruments use a permanent magnet as the source of the magnetic field. A Hall-effect generator or magneto-resistor is used to sense the magnetic flux density at a pole of the magnet. Electromagnetic induction instruments use an alternating magnetic field. A soft, ferromagnetic rod wound with a coil of fine wire is used to produce a magnetic field. A second coil of wire is used to detect changes in magnetic flux.
These electronic instruments measure the change in magnetic flux density at the surface of a magnetic probe as it nears a steel surface. The magnitude of the flux density at the probe surface is directly related to the distance from the steel substrate. By measuring flux density the coating thickness can be determined.
PosiTector users can capture and save an image copy of the current gage display by simultaneously pressing both the (-) and (+) buttons. 100 screen captures are stored in memory and can be accessed within the PosiSoft USB Drive.
Statistics mode continually displays/updates average, standard deviation, min/max thickness and number of readings while measuring.
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