Corrosion Performance and Protection of Centrifuged Hot-Dip Galvanized Coatings (CHDG) on St37 Steel Hooks in GFRC Façade Systems: A Case Study

St37 steel hooks are used to attach glass fiber-reinforced concrete (GFRC) panels to the surface of buildings. The corrosion products formed on the surface of the hooks cause tensile stresses in the surrounding concrete, resulting in cracking and potentially decreasing the load-carrying capacity of the hooks. It is, therefore, essential to protect these hooks from corrosion. Centrifugal hot-dip galvanizing (CHDG) is the preferred process, particularly for protecting small metal parts used in outdoor applications. This study is the first one aiming to investigate the protection effect of the CHDG coating on hooks used in the assembly of GFRC panels. GFRC panel hooks are often used in three different configurations during the assembly process. To evaluate this, the three most common hook assemblies were tested: unmounted (A), hooks embedded in GFRC (PD), and mounted with the hot-dip galvanized profile (KT). These were investigated for 96 hours at 23±2°C temperature and 50±5% relative humidity according to ASTM B117 standards, and the results are discussed. The cross-sectional morphologies of the St37 steel hook coated with CHDG before and after the salt spray test were examined using a scanning electron microscope (SEM) and energy-dispersive X-ray spectrometry (EDS). The test results show the absence of red rust in all the test specimens, indicating that the CHDG coating protects the tested hooks from corrosion. The formed ZnO layer allows the repair of coating defects and provides physical protection of the coatings against the penetration of aggressive ions.