A Variable Radius Roll Adhesion Test (VaRRAT) Suitable for Measuring The Adhesion of Paint to Metal

By Damien Jinks, Hugh Brown, David Buxton

Early trials and analysis of a new adhesion test are discussed. The test is designed for measuring the adhesion of paint to deformable steel sheets as used in building, automotive, and other cladding applications, and does not require detailed knowledge of the paint mechanical properties.

A stiff overlay, such as an epoxy resin, is applied to the coating, and the steel substrate is peeled away using a roll of well-defined radius to which the steel substrate is constrained. The propagation of a crack within the paint or at some interface in the paint/metal system depends mostly on the mechanical properties and thickness of the overlay and the radius of the constraining roll.

The test is shown to discriminate better than existing practical adhesion tests be-tween paints of expected differing adhesion/cohesion, but also presents some inconsistencies that require further work to resolve.