Applied stress on corrosion behavior of hot-dip galvanized steel in NaCl-NaHSO3 solutions

In this study, the stress corrosion behavior of hot-dip galvanized (HDG) steel was investigated in NaCl-NaHSO 3 solutions simulating marine-industrial atmosphere using a custom-designed constant-load apparatus. By comparing loaded specimens with unloaded controls, the work aimed to elucidate the influence of sustained mechanical loading on the corrosion evolution of HDG coatings. Surface characterization via scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) was employed to examine zinc coating degradation and identify corrosion product composition, while electrochemical techniques were used to quantify corrosion kinetics. The results indicate that bisulfite ions (HSO 3 - ) significantly increased solution corrosivity through acidification (i.e., H + release). Simultaneously, the nature of the corrosion products shifted from the relatively protective Zn 5 Cl 2 (OH) 8 to ZnSO 4 , which are porous, hygroscopic, and offer minimal barrier protection, thereby accelerating underlying Zn corrosion. Furthermore, the stress concentration at the bottom of pitting holes promoted crack initiation and ultimately led to Zn-coating failure. Critically, tensile stress and aggressive bisulfite ions synergistically altered the local thermodynamic and kinetic driving forces for anodic dissolution, while the applied stress level modulated the dominant factor of zinc corrosion.