Geometric characteristics of corrosion pits on high-strength steel wires in bridge cables under applied stress

In this study, the pitting corrosion depth of the high-strength steel wire surface divided by dense grids was obtained. The empirical threshold method was employed to make a decision on corrosion state for each grid. Connected corrosive grids were identified by traversing the grids and deemed individual corrosion pits. Then, the individual corrosion pits were characterised by corrosion pit area and volume, planar projection shape and three-dimensional morphology. By comparing the area and volume, it was found that the applied stress has an influence on the growth direction of the corrosion pit, i.e., it grows mainly along the depth direction compared to the growth under non-stressed conditions. For the planar projection shape, the aspect ratio b/a was selected as the shape indicator. For this purpose, different shape modes were found under different applied stress conditions. The skewness that describes the statistical distribution shape of the pitting corrosion depth was employed. In addition, the skewness of the statistical distribution of the pit corrosion depth for typical corrosion pits was determined to illustrate the relationship between skewness and corrosion pit morphology. It can be concluded that an applied high-level stress can affect corrosion pit morphology and it trends toward a needle-like type.