Interfacial delamination of a sandwich layer by aqueous corrosion

The mechanism of aqueous delamination of a methyl methacrylate -based adhesive layer, sandwiched between two steel plates, is investigated by a systematic series of critical tests. These tests include starving the specimen of oxygen, varying the aqueous environment from de-ionised water to water with a high concentration of salt, and varying the mechanical constraint imposed by the sandwich. Sandwich construction starves the delamination crack tip of oxygen, and delamination occurs by water attack of the interface. In contrast, an adhesive coating on a steel substrate undergoes cathodic delamination when oxygen is present at the crack tip and the delamination crack is filled with salt water.