Investigation of Corrosion Behavior of Mild Steel in Simulated Atmospheric Environments: A Review of Salinity Effects

Abstract

This review provides a systematic structural evaluation of the atmospheric corrosion mechanisms of low-carbon mild steel, focusing exclusively on the impacts of airborne marine salinity and localized chloride ion deposition. Structural steel elements located within maritime coastal environments undergo aggressive electrochemical deterioration driven by the high loading of windborne halide aerosols. This paper organizes and evaluates empirical data from standardized simulation configurations to isolate the chemical, thermodynamic, and microstructural consequences of chloride contamination on the structural iron matrix. Experimental data synthesis reveals that elevated chloride deposition rates up to 120 mg/m²/day shift uniform surface thinning to severe localized pitting, reaching a maximum measured pit depth of 0.85 mm. Under high salinity film concentrations of 3.5 wt.% NaCl, the thin-film solution conductivity increases drastically, pushing the electrochemical corrosion current density (I_corr) from a baseline of 1.2 µA/cm² up to 49.6 µA/cm². Long-term mineralogical phase analysis confirms that continuous marine chloride exposure alters the rust scale evolution, forcing the preferential crystallization of loose, unstable akaganeite (β-FeOOH) tunnel crystals until it reaches a dominant 68% share within 12 weeks. Consequently, high surface salt accumulation up to 100 mg/m² results in a dramatic increase in cumulative steel weight loss to 295 g/m², triggering extensive scale delamination and blistering. These quantitative outcomes provide crucial empirical benchmarks for selecting high-durability protective barriers and calculating accurate structural corrosion allowances within high-salinity marine boundary layers.