Epoxy's adhesion to metal is affected by surface treatment

Effects of Surface Treatment

On Epoxy Adhesion to Metals

by Brian Knight—GBI Technical Advisor

Above: Surface treatment can make all the difference in epoxy adhesion to metal. Photo by Manny Becerra on Unsplash 

We have performed tens of thousands of adhesion tests over the years and many of these tests were done on metal surfaces. Below is a summary of tests done on a variety of metal surfaces and done with a variety of surface preparations. As you look at the chart, notice the surface preparation that gives the highest number.

All the tests shown below were performed using a PATTI (pneumatic adhesive tensile test instrument) meter. We chose this test method as our default adhesion test method about 14 years ago because it yields consistent results, is relatively easy to perform, and is economical. The results shown below show the tensile strength of a glue joint. Not all joints are stressed in tension, so consider the data to be comparative, not a specification.

Most of the tests were done with WEST SYSTEM® 105 Resin/205 Fast Hardener or 105Resin/206 Slow Hardener. Most were allowed a two-week room temperature cure before the test was performed.

Effects of Surface Treatment on Epoxy Adhesion to Metals

Metal Cleaning Preparation Tensile adhesion (PSI)
sand 80-grit wet sand 1503
sand 80-grit 1065
2024 T3
sand 80-grit wet sand 1330
sand 80-grit 1126
Steel sand 80-grit 1320
sand 80-grit wet sand 1352
Lead (pure) sand 80-grit wet sand 2753
Cast Iron sandblast 3214
sand 80-grit wet sand 3970
Steel 316
sand 80-grit 957
sand 80-grit 974