Life prediction estimation of an underground pipeline using alternate current impedance and reliability analysis

In the present work, life prediction of a buried pipeline was estimated based on corrosion rates. From alternating current (AC) impedance measurements and by using a transmission line model, polarization resistance values of a buried structure were calculated with different coating defects exposed in different electrolyte conditions. A modification to the classic Stern-Geary equation was the basis to estimate corrosion rates that were used to calculate reliability functions for this metallic structure. By means of reliability functions, the expected life of an underground pipe under simulated field conditions was estimated. Using a mechanical model and assuming that corrosion is the control process in the failure initiation, and considering the random variability in the model and process at the interface metal-electrolyte, life prediction of a buried structure in laboratory conditions was determined.