STATISTICAL MODELING OF MILD-STEEL CORROSION UNDER MARINE ENVIRONMENTAL CONDITIONS AT A MAJOR SEAPORT

Abstract

Background: Marine environments expose metals to chloride and sulfate deposition, moisture, and changing atmospheric conditions that may accelerate corrosion. Understanding these relationships is essential for developing effective corrosion monitoring and maintenance strategies for marine infrastructure. Objective: This study aimed to assess marine atmospheric corrosivity at West Wharf, investigate associations between environmental exposure variables and mild-steel corrosion, and develop statistical models to characterize accumulated corrosion. Methods: Mild-steel coupons were exposed at West Wharf, and corrosion was quantified using the weight-loss method. Chloride and sulfate deposition rates and time of wetness (TOW) were measured during the observation period. Descriptive statistics, Pearson correlation analysis, polynomial regression, and multivariable regression modeling were used to examine environmental associations and characterize corrosion patterns. Model adequacy was evaluated using goodness-of-fit measures, the Durbin–Watson test, and heteroscedasticity diagnostics. Results: The mean chloride deposition rate, sulfate deposition rate, and TOW were 76.44 ± 19.62 mg/m²·d, 151.33 ± 30.78 mg/m²·d, and 1754.27 ± 1423.19 h, respectively. Mild-steel corrosion exhibited positive correlations with chloride deposition (r = 0.39) and TOW (r = 0.24), whereas the correlation with sulfate deposition was weak (r = 0.06). The polynomial regression model explained 93.9% of the observed variation in corrosion (R² = 0.939, p = 0.001), with statistically significant linear (p = 0.017), quadratic (p = 0.032), and cubic (p = 0.040) terms. The multivariable model explained 91.0% of the variation. Chloride deposition was positively associated with corrosion (β = 0.45, p = 0.043), whereas sulfate deposition showed a negative adjusted association (β = −1.42, p = 0.001). The lagged term was also statistically significant (β = 0.01, p = 0.007). Conclusion: Mild-steel corrosion at West Wharf was associated with variations in marine environmental exposure, with chloride deposition showing a positive relationship with corrosion. The fitted models may help characterize site-specific corrosion patterns and inform monitoring and maintenance planning. Further validation using independent observations and additional exposure periods is needed to establish their predictive reliability and generalizability.