Checkline AT-A User Manual

PosiTest Pull-Off Adhesion Tester

INSTRUCTION MANUAL v. 3.0

Simple. Durable. Accurate.

PosiTest AT

(manual)

PosiTest AT-A

(automatic)

Introduction

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 on a digital LCD and represents the
coating's strength of adhesion to the substrate.

In accordance with ASTM D4541, D7234, ISO 4624 and others, the PosiTest
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

.

Basic steps for testing coating adhesion with a PosiTest Adhesion Tester:

1. Dolly & Coating Preparation

The dolly and the coating are cleaned and abraded. (see pg. 4)

2. Adhesive & Dolly Application

The adhesive is prepared and applied to the dolly. The dolly is then adhered to
the coated surface and the adhesive is allowed to cure. (see pg.4)

3. Test Area Separation - Optional step

The test area of the coating is separated from the area surrounding the dolly by
cutting or drilling. (see pg. 5)

4. Pull-off Test

a) PosiTest AT (manual) (see pg. 6)
b) PosiTest AT-A (automatic) (see pg. 8)

5. Analysis of Test Results

The dolly and the coating are examined and evaluated to determine the nature
of the coating failure. (see pg. 10)

6. Store Pull-Off Test Results - Optional step

The PosiTest’s internal memory stores maximum pull pressure, pull rate, test
duration and dolly size for up to 200 pulls. (see pg. 10)

Page 3

Throughout this manual, the symbol indicates more information about

the particular topic or feature is available on our website.

Go to: www.defelsko.com/manuals

NOTE:

Step 1: Dolly & Coating Preparation

Step 1: Dolly & Coating Preparation

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 Preparation

1. Lightly roughen the coating using the included abrasive pad.

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.

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.

Step 2: Adhesive & Dolly Application

Step 2: Adhesive & Dolly Application

Adhesive Selection

The adhesive included in the PosiTest Adhesion Tester kit has been selected due
to its versatility. This adhesive has minimal impact on a variety of coatings and has
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. Quick curing one-part cyanoacrylates (super glues) may be sufficient for
painted surfaces, but two-part epoxies are preferred for porous or rough coatings.

Dolly Application

1. Mix the adhesive per manufacturer’s instructions and apply a uniform film of

adhesive on the base of the dolly (approximately 2-4 mils or 50-100 microns
for best results)

2. Attach the dolly to the prepared coating test area.

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.

Page 4

NOTE:

NOTE:

NOTE:

Page 5

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 with

included cotton swabs.

5. Allow to cure per the adhesive manufacturer's instructions

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.

Step 3: Test Area Separation

Step 3: Test Area Separation

Drilling Template

Cutting Instructions

1. Cut through the coating around the edges of the dolly with the included cutting

tool, removing any excess adhesive.

2. Clear away any debris from the cutting process.

-Cutting may induce coating surface flaws such as microcracking that
may alter test results.

-For coatings with strong lateral bonding it is recommended to cut
completely through the coating down to the substrate.

The decision of when to cut around a dolly is dependent on the standard,
specification or contractual agreement to which the test is to comply. The primary
purpose for cutting through the coating is to isolate a specific diameter test area.
When the decision to cut into the coating has been made, it is recommended to cut
all the way through to the substrate. As a minimum, it is suggested to carefully cut
away excess adhesive from the dolly application process. This typically prevents a
larger area of coating from being pulled away from the substrate, resulting in a
higher pull-off pressure.

When testing very thick coatings, an optional drilling template may be preferred.

NOTE:

NOTE: