Tafel-Piontelli model for the calculation of corrosion rate of metals in acidic condition. Validation tests in strong acids

摘要

Corrosion of metals in acidic environment is a concern in industrial applications, in particular in chemical and petrochemical industry. Material selection and corrosion rate prediction are mainly based on engineering practice and expertise, rather than on a robust theoretical approach, even if corrosion is nowadays a mature science. In this work, a mechanistic model for the calculation of corrosion rate of active metals in acidic condition is discussed and preliminary validation tests in strong acids are presented. The model, entitled to Julius Tafel and Roberto Piontelli, is derived from their own laws on corrosion kinetics of anodic (metal dissolution) and cathodic (hydrogen evolution) processes. The model calculates the corrosion rate of active metals, as carbon steel, in acidic condition. Preliminary validation tests were carried out on carbon steel specimens in strong acids (sulfuric and hydrochloric) at different pH (from 1 to 3) and temperature (20°C, 40°C). Potentiodynamic cathodic polarization curves were aimed to the extrapolation of the Tafel curve parameters (exchange current density and Tafel slope of hydrogen evolution reaction); corrosion rate was evaluated by mass loss rate.