Adoption of scanning probe electrochemical microscopy techniques for rebar corrosion study: Fundamental principle, current limitations, novel testing system and framework, and experimental case study

Reinforcing bar (rebar) corrosion is governed by highly localized electrochemical processes that are not adequately captured by conventional bulk techniques such as open circuit potential, polarization, and electrochemical impedance spectroscopy. This study evaluates the applicability of advanced scanning probe electrochemical microscopy (SPEM) techniques—including scanning electrochemical microscopy, scanning Kelvin probe, scanning vibrating electrode technique, and scanning droplet cell—for resolving microscale corrosion phenomena in rebar systems. A comprehensive review of their fundamental principles and cross-disciplinary applications is conducted to identify current limitations preventing their adoption in rebar corrosion studies, particularly challenges associated with corrugated geometries and embedded conditions in cementitious media. The criteria for transferability of SPEM techniques to rebar-concrete systems were defined, highlighting current challenges and recommended solutions, to support transitioning SPEM from proof-of-concept studies to reliable tools for reinforced concrete applications. Addressing some of these transferability challenges, this work develops a novel testing system and methodological framework that enables localized electrochemical characterization on ribbed and embedded rebar surfaces, as well as compares localized corrosion activity from SPEM techniques with bulk properties from traditional electrochemical measurements. These proof-of-concept case studies demonstrate that SPEM techniques can resolve spatial variations in electrochemical activity, distinguish active and passive regions, and provide mechanistic insights into corrosion initiation that are not detectable using conventional methods. Overall, this work lays the groundwork for further innovation in corrosion science and structural engineering by bridging advanced electrochemical characterization with real-world civil engineering challenges.