Proposed algorithm for life time prediction for small diameter low carbon steel pipelines under different scaling-flow simulation conditions

Internal corrosion is considered a serious treat for small diameter pipeline integrity due to the difficult to monitor the state of a structure when is under operation conditions. Electrochemical techniques based on time domain techniques such as potentidynamic polarization in laboratory conditions can estimate the corrosion rate under simulated operation conditions of metallic structures, whereas the technique based on frequency domain technique such as EIS (Electrochemical Impedance Spectroscopy) characterizes the interfacial process with time. In this work two electrochemical cells simulating different flow conditions are used to characterize the dissolution rate of carbon steel exposed scaling-cooling water solutions in presence and absence of 1,2-hydroxyphosphonoacetic acid (HPA) used as corrosion inhibitor. The corrosion rate magnitude can lead to the estimation of a finite dissolution time for the wall thickness of the metallic structure; however most of the lifetime calculation does not link the pressure with the corrosion rate. We propose as a first approach basis life prediction algorithm calculation based on the mechanical-dissolution rate of the pipe by using laboratory scale results. The time evolution damage by corrosion is modeled by a random walk, where corrosion rate, pressure of the pipe, inhibitor and fluid conditions are considered.