Experimentally verified thermodynamic framework for corrosion

Abstract

Utilizing the foundational principles of thermodynamics, this study characterizes material degradation resulting from corrosion, substantiating the outcomes through experimental verification. The proposed methodology establishes a unified corrosion model, effectively correlating entropy generation with measurable parameters, including potential difference, corrosion current, and temperature. The Degradation Entropy Generation (DEG) theorem is applied to establish a linear relationship between entropy generation and the degradation rate through a constant material property known as the degradation coefficient (B). Material degradation, quantified by assessing the material loss, is systematically examined with a focus on low-carbon steel (LCS 1018) and Al6061-T6. Corrosion experiments were conducted using a three-electrode electrochemical corrosion cell immersed in a 3.5 wt% NaCl aqueous solution. The degradation parameter, B, for both materials was assessed through multiple accelerated corrosion tests, where various magnitudes of potentials were applied to specimens with differing exposed areas. The presented results unveil a consistent degradation coefficient of (30±2)×10−9 m3K/J for LCS 1018 and (25±2)×10−9 m3K/J for Al6061-T6. To ascertain the generalizability of these findings under diverse environmental conditions, additional experiments are conducted on LCS 1018, exposing it to varying environmental parameters such as different percentages of NaCl solution, acidic conditions, and elevated solution temperatures. Remarkably, the degradation coefficient remains constant across all tested corrosive environments, attesting to its independence. This study offers a novel approach to understanding material degradation through a thermodynamic lens and demonstrates the applicability of the proposed corrosion model in diverse and challenging operational conditions.