Getting a grip on tensile adhesion testing
Posted by Tom Swan on Mar 25th 2020
a grip on tensile adhesion testing
These testing options work for several different PSI ranges.
You have a coated surface, and need to know the level of the bonding between the coatings and the substrate. You may have to do tensile adhesion testing, and you have several choices of test units. The final chapter in our Coating Inspectors Handbook explores this form of testing and which tester types have the highest level of pull.
There are 5 categories of adhesion testers defined by ASTM D4541. All five categories have different features which can cause the testers to measure the same coating system differently. That's all the more reason to be careful as you shop for the right meter. Operator knowledge may also affect how well any of these tests work.
Here are the specifics of each type and an appropriate tester to go along with them. These are based on ASTM D4541, "Standard Method for Pull-Off Strength of Coatings using Portable Adhesion Testers" which uses the terms Methods B-F (Method A or Type 1 was previously used but retired.):
The benefits of this tester is its portability and relatively easy means of use and you don't need power to use it. It is also one of the least expensive adhesion testers on the market.
On the Down side the accuracy is horrible (±40), the repeatability and the results depend on the operator using the unit, and it is only designed for 1 size of dolly.
"Each Type of tester can produce a wildly different result. That's all the more reason to be careful to choose the correct model."
Pricewise and performance wise this one is in the middle on both.
P.A.T.T.I. makes several models and has a new model suitable for field use. Units range rom $999 to about $5,000. Units come with one piston so others may need to be purchased if you need to pull dollies over a wider range.
For most situations this is the first choice for and adhesion tester. The automatic unit is $2,595.00 and is good for lab or field use.
The DFD adhesion tester have a self-aligning head to ensure perpendicular pulls. While they have excellent features, they are manual and suffer from inconsistencies due to operators. Also, they are very expensive but do fill a niche in the market. It is the only commercial tester I am aware of that can be adapted to ASTM C-633, “Standard Test Method for Adhesion or Cohesion Strength of Thermal Spray Coatings”
Don’t get lost in the numbers. It can be more important how the coating fails than the pull rate that the different units measure, We will leave that topic for a future blog.
Browse our store or read our Coating Inspectors Handbook to learn more about the right tensile adhesion test for you.
https://www.astm.org/Standards/D4541.htm http://www.m-testco.com/files/pages/The%20Coating%20Inspectors%20HandbookR5.pdf html http://www.m-testco.com/paint-application/inspection/adhesion-testing/hate-adhesion-tester/hate--test-kit--analog-p-670.html