A Study of Dynamic Nanoscale Corrosion Initiation Events by HS-AFM

A Study of Dynamic Nanoscale Corrosion Initiation Events by HS-AFM
Stacy Moore, Robert Burrows, Loren Picco, Tomas L. Martin, Scott J. Greenwell, Tom Scott and Oliver D. Payton
Published as a Faraday Discussions article in its first form as an Accepted Manuscript: Faraday Discussions, 2018, DOI: 10.1039/C8FD00017D

Atomic force microscopes (AFMs) are capable of high-resolution mapping of structures and the measurement of mechanical properties at nanometre scales within gaseous, liquid and vacuum environments. The contact mode high-speed AFM (HS-AFM) developed at Bristol Nano Dynamics Ltd. operates at speeds orders of magnitude faster than conventional AFMs, and is capable of capturing multiple frames per second. This allows for direct observation of dynamic events in real-time, with nanometre lateral resolution and subatomic height resolution. HS-AFM is a valuable tool for the imaging of nanoscale corrosion initiation events, such as metastable pitting, grain boundary (GB) dissolution and short crack formation during stress corrosion cracking (SCC). Within this study HS-AFM was combined with SEM and FIB milling to produce a multifaceted picture of localised corrosion events occurring on thermally sensitised AISI 304 stainless steel in an aqueous solution of 1% sodium chloride (NaCl). HS-AFM measurements were performed in situ by imaging within a custom built liquid cell with parallel electrochemical control. The high resolution of the HS-AFM allowed for measurements to be performed at individual reaction sites, i.e. at specific GB carbide surfaces. Topographic maps of the sample surface allowed for accurate measurements of the dimensions of pits formed. Using these measurements it was possible to calculate, and subsequently model, the volumes of metal reacting with respect to time, and so the current densities and ionic fluxes at work. In this manner, the local electrochemistry at nanoscale reaction sites may be reconstructed.

Provided here is the raw data taken for HS-AFM measurements, potentiostat measurements and the model used in COMSOL.
HS-AFM: The .hsafm files containing the raw data collected to produce the HS-AFM figures shown within the final paper. Analysis requires software from Bristol Nano Dynamics Ltd.
Potentiostat: Raw data from the potentiostat showing potentiodynamic scans and galvanostatic scans for pitting experiments.
COMSOL: The model used to generate figures for the final paper.

Further details are found within the paper.

高速原子力显微镜（High-Speed Atomic Force Microscope, HS-AFM）动态纳米级腐蚀起始事件研究
Stacy Moore、Robert Burrows、Loren Picco、Tomas L. Martin、Scott J. Greenwell、Tom Scott 及 Oliver D. Payton
本文以《Faraday Discussions》期刊接收稿件形式首次发表：《Faraday Discussions》，2018年，DOI: 10.1039/C8FD00017D

原子力显微镜（Atomic Force Microscope, AFM）可在气体、液体与真空环境中实现结构的高分辨成像，并在纳米尺度下测量力学性能。布里斯托纳米动力学有限公司（Bristol Nano Dynamics Ltd.）开发的接触式高速原子力显微镜（HS-AFM），其成像速度较传统原子力显微镜快数个数量级，可实现每秒多帧的图像采集，从而能够以纳米级横向分辨率与亚原子级高度分辨率实时直接观测动态过程。高速原子力显微镜（HS-AFM）是研究纳米级腐蚀起始事件的有力工具，例如应力腐蚀开裂（Stress Corrosion Cracking, SCC）过程中的亚稳态点蚀、晶界（Grain Boundary, GB）溶解与短裂纹形成。本研究将高速原子力显微镜（HS-AFM）与扫描电子显微镜（Scanning Electron Microscope, SEM）、聚焦离子束（Focused Ion Beam, FIB）刻蚀技术相结合，对热敏化AISI 304不锈钢在1%氯化钠（Sodium Chloride, NaCl）水溶液中的局部腐蚀事件进行了多维度表征。实验通过定制化液体池结合并行电化学控制实现原位高速原子力显微镜（HS-AFM）测量。得益于高速原子力显微镜（HS-AFM）的高分辨率，可在单个反应位点，即特定晶界碳化物表面开展测量。样品表面的拓扑形貌图可精确测量所形成点蚀坑的尺寸。基于这些测量结果，可计算并随后建模金属随时间反应的体积，进而解析反应过程中的电流密度与离子通量。通过该方法，可重构纳米级反应位点处的局部电化学过程。

本次公开的原始数据包含高速原子力显微镜（HS-AFM）测量数据、恒电位仪测量数据以及COMSOL仿真所用模型。
高速原子力显微镜（HS-AFM）：后缀为.hsafm的文件包含了用于生成最终论文中高速原子力显微镜（HS-AFM）图像的原始采集数据，该数据分析需使用布里斯托纳米动力学有限公司（Bristol Nano Dynamics Ltd.）提供的专用软件。
恒电位仪：原始恒电位仪数据，包含点蚀实验所用的动电位扫描与恒电流扫描结果。
COMSOL：用于生成最终论文插图的仿真模型。
更多细节请参见原文。