Mechanistic understanding of anodic stabilization in functionally designed low Ir multi-cationic oxide anodes for cathodic protection

Abstract

The present study investigates a series of non-stoichiometric multi-cationic oxide coated TM1-xIrxO/Ti (TM = Ni, Co, Sb and Ta

Ir = 0–25 wt.%) anodes for impressed current cathodic protection (ICCP) in 0.5 M Na2SO4 solution. The coatings were rationally designed by selecting multiple cations based on their functional roles, and the influence of Ir loading on their structural characteristics, electrochemical behaviour and anodic stability was systematically evaluated. Among the investigated compositions, the equimolar 20 wt.% Ir coating exhibited the extended accelerated lifetime (∼112 h) and the minimum specific consumption rate (4.22 × 10−7 g/Ah), while further increasing the Ir loading did not improve the anodic performance. The optimum composition exhibited a partially disordered oxide framework. Surface analysis confirmed predominantly Ir4+ together with mixed-valence Ni2+/Ni3+ and Co2+/Co3+, and a higher proportion of defect-related surface oxygen. Based on the structural, surface chemical and electrochemical characteristics, an anodic stabilization and degradation mechanism for the TM1-xIrxO/Ti coatings in neutral sulfate electrolyte is proposed. The results demonstrate that compositions approaching equiatomic cation fractions promote anodic stability by optimizing the oxide structure and surface chemistry, and providing a practical strategy for developing durable low-Ir multicationic oxide (MCO) anodes for cathodic protection. © 2026 Elsevier Ltd.