ADVANCED MATERIALS & PROCESSES | JULY 2026 20 original material and ensure adequate adhesion of subsequent treatments. Following surface preparation, a rust converter was applied as an anti- corrosive treatment, acting as a shop- primer, and subsequently covered with successive layers of final decorative synthetic enamel (Fig. 6). Therefore, the intervention cannot be understood as a simple corrosion protection process, but rather as an integrated approach involving material compatibility, structural integrity, and preservation of the original wrought iron. MICROSTRUCTURE AND MECHANICAL BEHAVIOR Metallographic observations revealed a heterogeneous microstructure typical of wrought iron, characterized by elongated slag inclusions distributed along the working direction of the material (Figs. 7 and 8). These inclusions generate a fibrous structure; a distinctive feature of iron produced through historical processes such as bloomery and subsequent puddling[4]. The inclusions were identified primarily as fayalite (Fe₂SiO₄) and wüstite (FeO), reflecting the physicochemical conditions of historical ironmaking. Because the melting point of FeO is higher than 1200°C, silica (SiO₂) was added to promote slag fluidity during processing. This results in a composite-like structure in which metallic iron is interspersed with slag phases. Despite its heterogeneity, this material has historically behaved as a “noble” material due to its toughness, damage tolerance, and long-term performance under service conditions[5]. Mechanical testing showed relatively low strength but significant ductility, consistent with the fibrous microstructure (Fig. 9). Charpy impact tests indicated an energy absorption capacity compatible with a material capable of accommodating defor- mation without brittle fracture (Table 2). These characteristics are directly related to the observed performance of the bridge, particularly its ability to withstand mechanical stresses and environmental exposure over long periods. In addition to their influence on mechanical behavior, elongated slag inclusions also play a role in corrosion response. The heterogeneous microstructure promotes localized electrochemical differences at the microscale. The orientation of these inclusions is not random. Historical forging pro- cesses imparted a preferential direction aligned with the working direction of the material. This anisotropic structure Fig. 7 — Metallography revealed a heterogeneous microstructure typical of wrought iron. Fig. 8 — The material is characterized by elongated slag inclusions distributed along the working direction. Fig. 9 — Mechanical testing showed relatively low strength but significant ductility, consistent with the fibrous microstructure. Fig. 6 — A rust converter was applied as an anticorrosive treatment and covered with successive layers of final decorative synthetic enamel.
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