Abstract
The properties of steels and other alloys are often tailored to suit specific applications through the manipulation of microstructure (e.g., grain structure). Such microscopic heterogeneities are also known to modulate corrosion susceptibility/resistance, but the exact dependency remains unclear, largely due to the challenge of probing and correlating local electrochemistry and structure at complex (alloy) surfaces. Herein, high-resolution scanning electrochemical cell microscopy (SECCM) is employed to perform spatially-resolved potentiodynamic polarisation measurements, which, when correlated to co-located structural information from electron backscatter diffraction (EBSD), analytical scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM), reveal the relationship between anodic metal (iron) dissolution and the crystallographic orientation of low carbon steel in aqueous sulfuric acid (pH 2.3). Considering hundreds of individual measurements made on each of the low-index planes of body-centred cubic (bcc) low carbon steel, the rate of iron dissolution, and thus overall corrosion susceptibility, increases in the order (101) < (111) < (100). These results are rationalized by complementary density functional theory (DFT) calculations, where the experimental rate of iron dissolution correlates with the energy required to remove (and ionise) one iron atom at the surface of a lattice, calculated for each low-index orientation. Overall, this study further demonstrates how nanometre-resolved electrochemical techniques such as SECCM can be effectively utilised to vastly improve the understanding of structure–function in corrosion science, particularly when combined with complementary, co-located structural characterisation (EBSD, STEM etc.) and computational analysis (DFT).
Highlights
The microstructural features of steel and other alloys, such as grains of different crystal orientation, grain boundaries and microscale inclusions, play an important role in the formation of the local anodic and cathodic cells that drive corrosion processes [1]
We have shown that under such conditions, scanning electrochemical cell microscopy (SECCM) measurements provide highly relevant data for understanding electron-transfer kinetics relevant to corrosion phenomena, as highlighted by the clear grain contrast in activity seen in electrochemical movies (SI, Movie 1)
We have advanced the understanding of the dependence of anodic iron dissolution on the underlying crystallographic structure of low carbon steel in aqueous sulfuric acid
Summary
The microstructural features of steel and other alloys, such as grains of different crystal orientation, grain boundaries and (sub) microscale inclusions, play an important role in the formation of the local anodic and cathodic cells that drive corrosion processes. Many studies have attempted to resolve the relationship between surface structure and electrochemical activity with metals such as iron [2e5], 316 L stainless steel [6] and aluminium [7] Such studies report that the crystal orientation does influence corrosion behaviour, a consistent trend or explanation for this behaviour has not been forthcoming. This is largely attributed to the difficulty in probing local electrochemistry and structure in the same area at complex surfaces, meaning that in practice measurements are often limited to a few measurements on single grains [8]. We attempt to rationalise these observations by complementary density functional theory (DFT) calculations
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
