DeFelsko PosiTest AT v.1.0 - Manual

PosiTest ® Pull-Off Adhesion Tester
Instruction Manual v1.0
Introduction
The portable, hand-operated PosiTest Pull-Off Adhesion Tester
measures the force required to pull a specified test diameter of
coating away from its substrate using hydraulic pressure. The
pressure is displayed in both MPa and PSI on a precision dial
indicator and can be related to the coating’s strength of adhesion
to the substrate.
In accordance with ASTM D4541-95 and ISO 4624, the PosiTest
Pull-Off Adhesion Tester evaluates the adhesion (pull-off
strength) of a coating by determining the greatest tensile pull off
force that it can bear before detaching. Breaking points,
demonstrated by fractured surfaces, occur along the weakest
plane within the system consisting of the dolly, adhesive, coating
layers and substrate.
There are a few basic steps for testing coating adhesion with a
PosiTest Adhesion Tester:
1. Dolly & Coating Preparation
o The dolly and the coating are cleaned and abraded.
2. Adhesive & Dolly Application
o The adhesive is prepared and applied to the dolly. The
dolly is then adhered to the coated surface and
adhesive is allowed to cure.
3. Test Area Separation
o The test area of the coating is separated from the area
surrounding the dolly by cutting or drilling. Drilling
(50mm or 20mm dollies) must be done before dolly is
adhered to the surface – cutting with hole-saw (20mm
dollies only) should be done after dolly is adhered and
adhesive is cured.
4. Pull-off Test
o After connecting actuator’s quick-coupling to the dolly,
pressure is pumped into the system and the dolly pulls
the coating(s) away.
5. Analysis of Test Results
o The dolly and the coating are examined and evaluated
to determine the nature of the coating failure.
Dolly Preparation
1. To remove oxidation and contaminants, place the included
abrasive pad on a flat surface and rub the base of the dolly
across the pad 4-5 times.
2. As required, remove residue left from the abrading process
using a dry cloth or paper towel.
Coating Surface Preparation
1. Lightly roughen the coating using the included abrasive pad
Note: As coating abrasion may introduce flaws, it should only
be used when necessary to remove surface contaminants,
or when the bond strength between the adhesive and the
coating is insufficient for pull testing.
2. To promote the bond between the dolly and the coating,
degrease the area of the coating to be tested using alcohol
or acetone to remove any oil, moisture or dust.
Note: Ensure that any alternative abrasion techniques,
degreasers or adhesives do not alter the properties of the
coating. Test by applying a small amount of degreaser or
adhesive to a sample area and observing effects.
Adhesive Selection
The adhesive included in the PosiTest Adhesion Tester kit has
been chosen as the recommended adhesive due to its versatility.
This adhesive has minimal impact on a variety of coatings and a
tensile strength exceeding the maximum performance
capabilities of the pressure system under ideal conditions. Other
adhesives may be preferred based on requirements such as
cure time, coating type, working temperature and pull off
strength, e.g., quick curing one-part cyanoacrylates (superglues)
may be sufficient for painted surfaces, but two-part epoxies are
preferred for porous or rough coatings.
Araldite ® Adhesive* Preparation
Using a wooden stir stick (included), mix equal parts of the
2011/A and 2011/B adhesive on one of the included cardboard
mixing palettes until the compound appears homogenous.
Adhering Dollies to Coating
1. Apply a uniform film of adhesive on the base of the dolly
(approximately 2-4 mils thick for best results)
2. Attach the dolly to the prepared coating test area.
Note: If the coated surface to be tested is overhead or vertical,
a means to hold the dolly in place during the cure time may
be required, i.e. removable tape.
3. Gently push down on the dolly to squeeze out excess
adhesive. Do not twist or slide the dolly back and forth on
the coating as air bubbles may be generated.
4. Carefully remove excess adhesive from around the edges of
the dolly.
5. Allow to cure per the adhesive manufacturer’s instructions
Note: Many adhesives cure faster and provide a stronger bond
when cured with heat. Similarly, cold environments may
cause a longer cure time and weaker bond strength.
Final Dolly Preparation
Cutting Instructions:
1. Cut through the coating around the edges of the dolly with
the 20 mm cutting tool, removing any excess adhesive.
2. Clear away any debris from the cutting process.
Note: Cutting may induce coating surface flaws such as
microcracking that may alter test results.
Note: For coatings with strong lateral bonding it is
recommended to cut completely through the coating down to
the substrate.
Drilling Instructions:
1. Place template on the coating to be tested. With a hand-drill
(using a 5/32” / 4.0 mm drill bit) drill the first positioning hole
into the coating through the hole marked No.1. While drilling,
always hold template firmly against the coating. After drilling,
remove the template and remove debris from surface.
2. Reposition the template and insert one of the two attached
pins through the template hole marked No.1 and into the
first drilled positioning hole.
3. Drill the second positioning hole into the coating through the
template hole marked No.2. After drilling, remove the
template and remove debris from surface.