Effects of marine salt corrosion on hygrothermal properties of porous building envelope materials: A review

Marine salt corrosion poses a significant threat to coastal buildings. While the corrosion resistance of structural components is relatively well understood, the degradation of hygrothermal properties in envelope materials—such as plaster mortar, aerated concrete, and stone—remains overlooked, negatively impacting thermal performance and durability. To address this gap, this study provides a comprehensive review that highlights the processes of salt deposition and diffusion, their effects on porosity, hygric, and thermal-optical properties, as well as recent advancements in mitigation strategies. The review reveals five key findings: (1) Wind is a crucial factor influencing the generation and deposition of salt on building facades; however, the impact of building type and urban layout on these processes is often overlooked, representing a fundamental boundary issue; (2) The absence of standardized experimental protocols for assessing changes in hygrothermal properties following salt ingress—characterized by inconsistent salt concentrations and cycle counts—impedes meaningful comparative analyses; (3) The impact of marine salt erosion on the hygrothermal parameters of building materials is often neglected, preventing the establishment of a comprehensive hygrothermal parameter database; (4) There is a lack of a systematic prevention system for salt spray corrosion in outer protective structures, with mitigation strategies for critical junctions (such as windowsills and curtain wall connectors); (5) A comprehensive model that evaluates the entire salt spray process—from generation and deposition to migration and parameter impacts—remains undeveloped, hindering the creation of accurate assessment and mitigation strategies. Specific recommendations based on these findings have been provided. Further research is essential to bridge these gaps and enhance the resilience of buildings against marine salt corrosion.