A FAST AND POTENTIALLY NON-DESTRUCTIVE DIAGNOSTIC TOOL FOR ENVIRONMENTALLY AFFECTED METAL STRUCTURES

A variety of structures is exposed to aggressive environmental conditions that induce damaging processes like corrosion and hydrogen assisted cracking. This latter phenomenon affects, among others, metal components of novel and traditional infrastructures in the strategic energy sector, like wind turbine towers and pipelines for gas transportation. A progressive degradation of the bulk material properties is provoked by the absorption of hydrogen through the metal walls. The most pronounced effect is toughness reduction, increasing the risk of failure under operating conditions due to brittle fracture or bursting. The residual lifetime of environmentally affected structures can be estimated by predictive models of the ongoing electro-chemical reactions and of their progressive diffusion, supported by the continuous monitoring of the evolving material characteristics. The current mechanical status is usually evaluated in laboratory, on specimens cut and worked out from the structure and subjected to standardized tests. However, the often observed correlation between phenomena like hydrogen embrittlement and the variation of parameters like the material overall strength, suggests the use of alternative, potentially non-destructive methodologies based on indentation tests carried out on site, on the external surface of the component. This fast and cheap diagnostic tool may be eventually integrated by through thickness investigations of small material portions extracted from the most critical sections only.