Abstract
For the first time fracture mechanical properties of scales from wet corrosion were considered with respect to the initiation steps of flow induced localized corrosion (FILC) of steel under conditions of scale forming corrosion processes. Fracture mechanical data for iron carbonate scales from carbon dioxide corrosion, assessed by first principle considerations, were compared with own experimental data in a failure mode diagram which correlates the tendency of scale spalling with scale thickness related critical strains. Inhibitors influence the fracture mechanical properties of corrosion product scales by reducing their thickness, porosity and intrinsic growth stresses. The destruction and spalling of iron carbonate scales is primarily the effect of intrinsic stresses. Extrinsic stresses like wall shear stresses in flowing media are generally too small to contribute much to the local destruction of scales. FILC is initiated at sites of local spalling if critical flow intensities prevent re-formation of protective scales.
