Micro-scale potentiodynamic polarisation curves of 316L stainless steel

This database comprises 5 Potentiodynamic Polarisation (PP) datasets. Each dataset consists of a pair of CSVs: 1 file containing the values of the applied potential scan rate (mV/s); and 1 having the corresponding current density j (µA/cm²) values.

This database was first deployed in the following scientific article, accepted for publication in Corrosion Science journal on 10 March 2023:
"Probing the randomness of the local current distributions of 316L stainless steel corrosion in NaCl solution".
Leonardo Bertolucci Coelho1,2,∗, Daniel Torres1, Miguel Bernal1, Gian Marco Paldino3, Gianluca Bontempi3, Jon Ustarroz 1,2
1 ChemSIN – Chemistry of Surfaces, Interfaces and Nanomaterials, Université libre de Bruxelles (ULB), Brussels, Belgium
2 Research Group Electrochemical and Surface Engineering (SURF), Vrije Universiteit Brussel, Brussels, Belgium
3 Machine Learning Group (MLG), Université libre de Bruxelles (ULB), Brussels, Belgium
*[e-mail]

955 PP curves were recorded on the same 316L sample using the Scanning Electrochemical Cell Microscopy (SECCM) in hopping-mode protocol. A total of 12 SECCM sessions were performed, comprising maps with up to 17x17 points (during up to 24 h of continuous measurement).
Five different combinations of [NaCl] and voltammetric scan rates were employed: 0.005 M NaCl – 100 mV/s, 0.01 M NaCl – 100 mV/s, 0.01 M NaCl – 50 mV/s, 0.05 M NaCl – 100 mV/s, 0.05 M NaCl – 50 mV/s. The number of data samples (j Vs E curves) is 287, 377, 119, 125 and 47 for each dataset. These quantities of curves were considered representative of each testing condition, as the underlying j distributions were continuous.
The datasets were sliced from 0.5 V Vs Ag/AgCl (considerably more positive than the OCP) upward to avoid the eventual and deleterious occurrence of negative currents. Positive j values were preferred for building histograms and obtaining defined log(j) numbers.
The SECCM experiments were designed to detect low corrosion currents, and the trade-off for such a high signal sensitivity was the I saturation level at 10 nA. In case of missing data points in the anodic sweep data (most often caused by oversaturation at high applied overpotentials), these were replaced by data interpolation (Python pandas interpolate() method, spline). This data-filling procedure was used for a small proportion of the data populations (0%, 0%, 1%, 1% and 11%, respectively, for the datasets with increasing testing aggressiveness). The final shapes of the j Vs E curves were validated against similar curves with unsaturated signals at the relevant E ranges.

本数据库包含5组动电位极化（Potentiodynamic Polarisation, PP）数据集。每组数据集均由一对逗号分隔值（Comma-Separated Values, CSV）文件组成：其一存储施加的电位扫描速率（单位：mV/s）数值，其二存储对应的电流密度j（单位：µA/cm²）数值。

本数据库首次刊载于2023年3月10日被《Corrosion Science》期刊接收的学术论文："Probing the randomness of the local current distributions of 316L stainless steel corrosion in NaCl solution"，其中文译名为《探究NaCl溶液中316L不锈钢腐蚀的局部电流分布随机性》。作者包括Leonardo Bertolucci Coelho1,2,∗、Daniel Torres1、Miguel Bernal1、Gian Marco Paldino3、Gianluca Bontempi3、Jon Ustarroz 1,2；所属机构如下：
1 布鲁塞尔自由大学（Université libre de Bruxelles, ULB）表面、界面与纳米材料化学研究室（ChemSIN），比利时布鲁塞尔
2 布鲁塞尔自由大学（Vrije Universiteit Brussel）电化学与表面工程研究组（SURF），比利时布鲁塞尔
3 布鲁塞尔自由大学（Université libre de Bruxelles, ULB）机器学习研究组（Machine Learning Group, MLG），比利时布鲁塞尔
*通讯邮箱：[e-mail]

研究采用跳跃模式扫描电化学细胞显微镜（Scanning Electrochemical Cell Microscopy, SECCM），在同一块316L不锈钢试样上记录了955条PP曲线。实验共开展12次SECCM测试，所得扫描图谱最多包含17×17个测点，单次连续测量时长可达24小时。

实验设置了5组不同的NaCl浓度与伏安扫描速率组合：0.005 M NaCl – 100 mV/s、0.01 M NaCl – 100 mV/s、0.01 M NaCl – 50 mV/s、0.05 M NaCl – 100 mV/s、0.05 M NaCl – 50 mV/s。各组数据集对应的j-E曲线样本量分别为287、377、119、125和47。由于各测试条件下的电流密度分布均为连续分布，上述样本量被认为可充分代表对应测试场景。

为避免出现有害的负电流，所有数据集均从相对于Ag/AgCl参比电极的0.5 V（远高于开路电位（Open Circuit Potential, OCP））开始，向上截取至阳极扫描区间。为构建直方图并获得明确的log(j)数值，实验优先采用正电流密度数据。

本SECCM实验旨在检测极低的腐蚀电流，而为实现高信号灵敏度，实验将电流饱和阈值设定为10 nA。若阳极扫描数据存在缺失测点（多数因高施加过电位下信号过饱和导致），则采用样条插值法（通过Python pandas的interpolate()函数实现）进行补全。按测试腐蚀性由弱到强排序的5组数据集，其缺失数据补全比例分别为0%、0%、1%、1%和11%。最终得到的j-E曲线形态，已通过在对应电位区间内未饱和信号的同类曲线完成验证。