Moving Beyond Cross Hatch: The Stood-Up Drop® Technique as a New Route to Assess Coating Adhesion

Correlating the dewetting angle with ISO2409:2020 test results

The humble contact angle measurement is an essential part of any coatings specialist’s toolbox, used to quantify wettability, (re)coatability, defect occurrence, cleanliness, and more. For decades, a considerable effort has been invested in determining the relationship between contact angle and coating adhesion. Observations reveal that this approach works well for some systems but not at all for others. Because of this, contact angle measurements are often supported – or replaced – by destructive methods the most well-known of which being cross hatch/crosscut (tape), and pull-off (dolly) tests. While destructive tests are commonplace across many industries, like automotive, aerospace, electronics, marine, packaging, etc., their use is not ideal due to issues with subjectivity, expertise required, quantification of results, and the time to measure (typically 24 – 48 hours, depending on curing time of the coating).

In this work, we demonstrate the importance of choosing the most suitable type of contact angle when assessing adhesion. Specifically, the new KRÜSS Stood-up Drop® method, which captures dewetting behavior, is shown to quickly generate results that reliably predict adhesion performance of a coating on different substrates.