How to Test Sealers for Adhesion

By Chris Sullivan – ChemSystems, Inc.

Question:

How do I know if the sealer on my stamped concrete patio is still working, or if it's beginning to lose adhesion and needs to be stripped and replaced?

Answer:

There are two common ASTM field tests for determining sealer adhesion in the field, known as "tape tests." The specific application and performance criteria for these tests are described in ASTM D3359, "Standard Test Method for Testing Adhesion by Tape Test," available at ASTM International.

The first of the two tests is the X-cut test and is primarily intended for use with coatings on metal substrates. The test better suited for the thin-build sealers and coatings often used on decorative concrete is the cross-hatch test. It provides the best results on coatings less than 5 mils (125 microns) thick. The test consists of a cross hatch, or "#" pattern, cut into the sealer or coating with a sharp razor blade or scalpel. A cutting guide or special cross-hatch cutter should be used if testing per ASTM specifications. For a simple field test to determine adhesion, hand cutting will suffice. After making the cross-hatch incision, apply pressure-sensitive tape or clear plastic packing tape over it and then rub over the tape until it is well adhered to the sealer or coating. Next, remove the tape and assess the results per ATSM D3359 guidelines. If the sealer is well adhered, the cross-hatch pattern should be clean with very little or no sealer removed by the tape. If the sealer is exhibiting adhesion failure, the cross-hatch cuts will have rough edges and sealer may be present on the tape. If the coating can be easily removed at the cut marks, this is another indication that the sealer is compromised and may no longer be well adhered to the substrate.

Cross-hatch test for sealer adhesion being performed on stamped concrete.