schilwerking

Schilwerking is a term used in Dutch-language coatings science and structural materials to describe a failure mode in which a thin outer shell or skin forms on a substrate and then separates, peels, or flakes off. It is a common phenomenon in layered systems such as paint films on metal or wood, ceramic glazes, protective coatings, and some composite laminates. The shell can be partially detached while still bonded at the edges, leading to edge curling, blistering, or spallation of the outer layer.

Typical causes include differential thermal expansion and moisture movement between layers, aging and degradation of the binder, ultraviolet exposure, contamination of the substrate, inadequate surface preparation, incompatibility between coating layers, and excessive coating thickness. The resulting mechanical and adhesive stresses drive delamination and shell formation, reducing protection as well as aesthetics.

Diagnosis relies on visual inspection and cross-sectional analysis, often supported by adhesion tests (for example pull-off tests) and, in non-destructive cases, ultrasonic or infrared techniques to locate subsurface delamination. Prevention and remediation focus on compatible materials and proper application: thorough surface preparation, selection of primers and topcoats with compatible mechanical properties, controlling environmental conditions during curing, and avoiding excessive film thickness. In existing installations, localized removal and re-coating may be required to reestablish bond integrity.

Etymology: "schil" means shell in Dutch, and "werking" indicates the process or mechanism. See also delamination, flaking, blistering, spalling.