Screening the Surface Structure-Dependent Action of a Benzotriazole Derivative on Copper Electrochemistry in a Triple-Phase Nanoscale Environment

Abstract

Copper (Cu) corrosion is a compelling problem in the automotive sector and in oil refinery and transport, where it is mainly caused by the action of acidic aqueous droplets dispersed in an oil phase. Corrosion inhibitors, such as benzotriazole (BTAH) and its derivatives, are widely used to limit such corrosion processes. The efficacy of corrosion inhibitors is expected to be dependent on the surface crystallography of metals exposed to the corrosion environment. Yet, studies of the effect of additives at the local level of the surface crystallographic structure of polycrystalline metals are challenging, particularly lacking for the triple-phase corrosion problem (metal/aqueous/oil). To address this issue, scanning electrochemical cell microscopy (SECCM), is used in an acidic nanodroplet meniscus|oil layer|polycrystalline Cu configuration to explore the grain-dependent influence of an oil soluble BTAH derivative (BTA-R) on Cu electrochemistry within the confines of a local aqueous nanoprobe. Electrochemical maps, collected in the voltammetric mode at an array of >1000 points across the Cu surface, reveal both cathodic (mainly the oxygen reduction reaction) and anodic (Cu electrooxidation) processes, of relevance to corrosion, as a function of the local crystallographic structure, deduced with co-located electron backscatter diffraction (EBSD). BTA-R is active on the whole spectrum of crystallographic orientations analyzed, but there is a complex grain-dependent action, distinct for oxygen reduction and Cu oxidation. The methodology pinpoints the surface structural motifs that facilitate corrosion-related processes and where BTA-R works most efficiently. Combined SECCM–EBSD provides a detailed screen of a spectrum of surface sites, and the results should inform future modeling studies, ultimately contributing to a better inhibitor design.

The New Era of High-Throughput Nanoelectrochemistry

“…Chronopotentiometry measurements were performed (Figure B) under O 2 or Ar atmosphere to highlight key electrochemical processes underpinning localized Cu corrosion across a wide range of surface structural facets and grain boundaries identified by colocated EBSD . In a follow-up study employing voltammetric mode SECCM, the efficiency of an oil-soluble derivative of the classic Cu corrosion inhibitor benzotriazole was quantified for both anodic (copper dissolution) and cathodic processes, presented against structural variations of the surface . Another model system explored by a similar approach was the dissolution of Ag and its local reaction kinetics.…”

The new era of high throughput nanoelectrochemistry

“…226 In a follow-up study employing voltammetric mode SECCM, the efficiency of an oil soluble derivative of the classic Cu corrosion inhibitor benzotriazole was quantified for both anodic (copper dissolution) and cathodic processes, presented against structural variations of the surface. 260 Another model system explored by a similar approach was the dissolution of Ag 261 and its local reaction kinetics. Voltammetric mapping and additional co-located AFM characterization allowed extensive analysis of the dissolution mechanism and the prominent role of surface grain boundaries.…”

Reflective microscopy for mechanistic insights in corrosion research

“…Nanoscale resolution imaging should be possible using the advanced optics equipment [13] that would place RM in the same category as the state-of-the-art electrochemical scanning probes [36] (for example scanning electrochemical cell microscopy (SECCM) [6]), widely used for characterization of polycrystalline metal electrodes. [37,38] We would like to emphasize that despite of extreme importance of investigation of the surface film conversion in corrosion field, these developments are still applied to a very limited number of systems and experimental conditions awaiting its wide-spread application.…”

“…In particular, emerging nanopipets methods (scanning ion conductance microscopy (SICM) and SECCM) offer a wealth of capabilities complementary to optical observations: [44] nanoscale measurements of corrosion currents and potentials, localized measurement of surface charges, localized inhibitor delivery via nanopipet injection etc., [6,45,46] all essential in corrosion research. For example, SECCM, already used to map corrosion relevant data on polycrystalline metal interfaces and alloying intermetallics, [37,38,47] does not provide in-situ information on evolution of surface films that can be easily observed if coupled with RM. [44] SECCM can also be used to deposit droplets of corrosive electrolyte and create thin water films on metal interfaces.…”