Coating Thickness Measurement on Concrete & Masonry Substrates
200 ultrasonic coating thickness gage
is ideal for non-destructively measuring the dry film thickness
of coatings on concrete and masonry substrates.
Masonry substrates include stone, brick,
tile, cast concrete, pre-cast concrete, concrete block,
asbestos-cement board, renderings and plasterboard.
Masonry substrates are often porous with varying degrees
of surface roughness. While useful in promoting adhesion,
such porosity and roughness increases the difficulty
in attaining repeatable thickness measurements.
Masonry coatings are used for a multitude of purposes including cosmetic appearance, durability, abrasion resistance, as well as protection from elements such as moisture, salt, chemical and ultra-violet light. Common coatings for concrete include latex paints, acrylics, lacquers, urethanes, epoxies, and polyester resins.
Primer layers are used as adhesion promoters, while overcoat layers serve as protection from surrounding elements. The ability of the PosiTector 200 to discern individual layers of coating is dependent upon the acoustic properties of adjacent layers, individual layer thickness, as well as the coating process itself.
The primary purpose for measuring coating thickness on concrete is to control coating costs while ensuring adequate protective coverage. Commercial contracts often require an independent inspection of the work upon completion.
A non destructive test method eliminates the need to repair the coating after inspection, saving time for both the inspector and the contractor.
Traditionally a destructive test method is
used to determine coating thickness on masonry substrates
such as concrete. Coatings used on concrete range from hard
to soft, smooth to textured, and cover a wide thickness range.
The surface of concrete can be quite rough, which can create
significant variations in thickness measurements.
The ultrasonic PosiTector 200 C
(standard or advanced) gage is ideal for measuring most coating
on concrete applications. With a coating thickness measurement
range of 50 to 3800 µm (2 to 150 mils), this gage is recommended
for customers desiring a single non-destructive measurement
solution for most applications. The PosiTector 200 C requires
little or no calibration adjustment for most applications.
Figure 1 provides a cross-sectional view of a representative
125 to 375 µm (5 to 15 mil) coating on large aggregate concrete
that is ideal for the PosiTector 200 C.
Figure 1: Coating on rough, large aggregate concrete
The ultrasonic PosiTector 200 B
gage is ideal for measuring coating thickness from 13 to 1000
µm (.5 to 40 mils). While not specifically designed for measuring
on concrete, after a simple calibration adjustment the 'B'
probe may demonstrate improved repeatability when measuring
hard, thin coatings over smooth surfaces. Figure 2 represents
an application where the PosiTector 200 B
may be preferred.
Figure 2: Thin coating on smooth, cement
If the concrete surface is smooth but uneven,
or rough and porous, one would expect the measurement values
to vary accordingly. When examined under magnification, locations
where the coating has flowed into pores or crevices may appear
as outliers when measurements are taken. For example in Figure
3, the bump in the substrate at "A" results in a significantly
different thickness than nearby point "B". It is up to the
user to compare results to the specification or expected thickness
when analyzing results. Some results may need to be omitted
when making calculations.
Figure 3: Thick soft coating on concrete
For an application such as Figure 4, that has both a rough substrate and a rough coating surface, it may be necessary to take several readings within individual small areas, calculate average readings, and then compare these values. These averages can then be compared against the specification. Destructive testing on the sample shown in Figure 4 identified a 1 to 3 mm (40 to 115 mil) variation within a Ľ” diameter area.
Figure 4: Coating on rough lightweight concrete
How to Measure
Ultrasonic testing measurement works by sending an ultrasonic vibration into a coating using a probe (i.e. a transducer) with the assistance of a couplant applied to the surface. A 4 oz bottle of a common water-based glycol gel is included with every instrument. Alternatively, a drop of water can serve as couplant on smooth, horizontal surfaces.
Figure 5: Taking
After the drop of couplant has been applied
to the surface of the coated part, the probe is placed flat
on the surface. Pressing down initiates a measurement (see
Fig. 5). Lifting the probe when a double beep is heard holds the last measurement
on the LCD. A second reading may be taken at the same spot
by continuing to hold the probe down on the surface. When
finished, wipe the probe and the surface clean with a tissue
or soft cloth.
Graphics Mode (PosiTector 200 Advanced Models Only)
The right hand side of the PosiTector 200's screen can be used to display a graphical representation of the ultrasonic pulse as it passes through the coating system. This powerful tool enables the user to better understand what the gage "sees" below the surface of the coating.
Figures 6 & 7:
Left: PosiTector 200 C3 with Graphics
Right: PosiTector 200 C3 with Memory Mode ON
thickness gage is ideal for coating thickness measurement
over a variety of non-metal substrates.
Two models are ideal for masonry coatings:
1. The PosiTector 200 C1 is the economical
and most common solution for measuring the TOTAL coating system
2. The PosiTector 200 C3 is capable of measuring
both TOTAL coating thickness AND up to 3 individual layer
thicknesses in a multi-layer system. It also features a graphic
readout for detailed analysis of the coating system.
Each PosiTector 200 comes complete
with probe, protective rubber holster
with belt clip, couplant, 3 AAA batteries, instructions, nylon
carrying case with shoulder strap, Certificate of Calibration
traceable to NIST, two (2) year warranty.
Size: 146 x 64 x 31 mm (5.75" x 2.5" x 1.2")
Weight: 165 G (5.8 oz.) without batteries
Conforms to ASTM D6132 and ISO 2808
For current pricing or to order these instruments, please contact us by e-mail at firstname.lastname@example.org, by telephone at +1(315) 393-4450 or by fax at +1(315) 393-8471. If you require additional technical information or have questions relating to your particular application, we encourage you to take advantage of our years of experience in recommending the best gage for your needs.