Galvanic Corrosion Behavior of H59 Brass Coupled with Electrogalvanized and Hot-Dip Galvanized Bolts in a Salt Spray Environment

Neutral salt spray tests were conducted on assemblies comprising H59 brass and either electrogalvanized or hot-dip galvanized bolts. The polarization curves, electrochemical impedance spectroscopy (EIS), corrosion morphology, elemental distribution, and corrosion product composition of the H59 brass were systematically characterized. The results demonstrated that upon coupling with galvanized bolts, the formation of a protective Cu2O film on the H59 brass is significantly weakened, leading to accelerated corrosion. After coupling with electrogalvanized bolts, the icorr reached a maximum value of 0.21 mA/cm2. A corrosion layer predominantly composed of ZnO formed on the sample surface with a thickness of approximately 13 μm, and no penetration or enrichment of Cl was observed in the matrix. More seriously, when the brass was assembled with hot-dip galvanized bolts, the icorr never dropped below 0.2 mA/cm2. A porous and complex Zn-Cu-O-Cl mixed corrosion layer developed on its surface. This loose structure allows Cl− to reach a depth of 55 μm into the matrix and continue causing corrosion. The mechanisms underlying the different corrosion behaviors of H59 brass caused by different galvanizing bolt processes require further investigation.