2. Selecting the Dolly Diameter and Gauge - Pull-Off Adhesion Test

New and updated edition.

When testing coating adhesion using a pull-off adhesion tester, there are a range of dolly sizes and gauge types to choose from; and your pull off adhesion test application will affect the dolly (tensile stub) or gauge you choose.

There are a number of pull off adhesion gauge design types. These include:

- mechanical gauges such as the Elcometer 106 (ASTM D4541 Type II);

- hydraulic push off gauges such as the Elcometer 108 and 508 (ASTM D4541 Type III);

- and hydraulic pull off gauges, such as the manual Elcometer 506, and the automatic Elcometer 510 (ASTM D4541 Type V) – which are available with various dolly skirts for the different dolly sizes or substrate thicknesses.

When it comes to choosing a dolly or tensile pull stub, whilst a 20mm diameter dolly is most commonly used to test coating adhesion on most substrates, there are different sized dollies for different applications.

When the adhesive value of a coating is expected to be very high, use a smaller sized dolly, as the smaller the diameter, the higher the achievable tensile force.

So 50mm dollies, for example, are designed for testing coatings on concrete or if the adhesion is expected to be very low.

14.2 and 10mm dollies, on the other hand, are typically used for testing small areas, curved surfaces, or when the adhesive value of the coating is expected to be very high.

All pull-off adhesion testers follow the same principle. A properly prepared dolly, or pull stub, is glued to the prepared coating, and, once the glue has fully cured, the dolly is pulled off -perpendicularly (or 90 degrees) from the surface. The resultant tensile pull-off force, together with the dolly diameter, and the conditions of the dolly, are all recorded.

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STANDARDS:

Elcometer 106

AS 1580.408.5, ASTM D 4541, AS/NZS 1580.408.5, EN 13144, EN 24624, ISO 4624, ISO 16276-1, JIS K 5600-5-7, NF T30-062, NF T30-606

Elcometer 106/6

ASTM D 7234, BS 1881-207, DIN 1048-2, EN 1542, EN 12636

Elcometer 506

ASTM D4541, ASTM D7234, AS/NZS 1580.408.5, BS 1881-207, DIN 1048-2, EN 12636, EN 13144, EN 1542, EN 24624, ISO 16276-1, ISO 4624, NF T30-606, NF T30-062

Elcometer 510

ASTM C1583, ASTM D4541, ASTM D7234-12, AS/NZS 1580.408.5, BS 1881-207, DIN 1048-2, EN 1015-12, EN 12636, EN 13144, EN 1542, EN 24624, ISO 16276-1, ISO 4624, NF T30-606, NF T30-062