Localised corrosion on reinforced concrete structures: Pitting factor analysis

Pitting corrosion has become one of the main causes of premature deterioration in reinforced concrete structures exposed to marine environments. This phenomenon is particularly critical for structural reliability, as it leads to a more severe reduction in the cross-sectional area of reinforcing bars compared with uniform corrosion. Over the past four decades, numerous studies have focused on evaluating the pitting factor ( R pit ), a parameter that relates the uniform corrosion depth ( P x ) to the maximum pit depth ( P pit ). However, the values reported in the literature exhibit considerable variability. In this experimental study, pitting-induced damage was investigated in reinforced concrete specimens immersed in seawater for 320 days. Detailed pit characterisation was conducted on 72 reinforcing bars using three-dimensional (3D) scanning. The results, complemented by the analysis of an additional dataset of 368 values compiled from the literature, show that R pit cannot be regarded as a constant parameter, as it mainly depends on the extent of corrosion, exhibiting lower values at more advanced stages of degradation. The method used to induce corrosion also influenced R pit , although this effect became negligible at higher degradation levels. For chloride-induced corrosion, where chlorides were not incorporated during concrete mixing, the experimental results revealed a robust power-law relationship between P x and R pit . Based on these findings, an empirical equation describing this relationship is proposed, represented by the 95th percentile curve of the experimental data. • Detailed pit characterization was conducted using three-dimensional (3D) scanning. • A linear relationship was identified between each pit area and its maximum depth. • Pitting factor R pit is not a constant value; it decreases as corrosion progresses. • Corrosion induction method influences R pit , which is lower when chlorides are cast-in. • Results show a strong power-law correlation between average corrosion depth and R pit