National Physical Laboratory

Coating Adhesion and Fracture Assessment

Delamination of different coatings in flexure testDelamination of different coatings 
in flexure test 

Surface performance is critical to almost every engineering material, and the ability to apply a durable coating (functional and/or decorative) is a key requirement. The integrity of such coatings is a major performance requirement as the cost of failure may be significant. Quality assurance of coated structures at the time of manufacture is critical to ensure that sub-standard components, with a reduced lifetime, are not put into service

NPL, in collaboration with TWI, has investigated techniques for the non-destructive evaluation (NDE) of coatings. The project has concentrated on a range of functional engineering coatings as well as paints. These have been evaluated using over 10 different NDE methods including thermography, C-scan ultrasonics and laser shearography.

The main conclusion is that there is not one technique that can be universally applied to all possible coating types, a major factor being the thickness of the coating.

Flash thermography has proved particularly useful in detecting areas of delamination on vapour deposited chromium nitride (5 microns) on steel, whilst terahertz pulsed imaging has been able to detect suspect areas on painted marine structures.


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Last Updated: 25 Mar 2010
Created: 28 May 2009


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