Electrochemical Corrosion Behavior of Carbon Fiber Reinforced Plastic and 30CrMo Bolted Joints in a Salt Spray Environment

ABSTRACT The electrochemical corrosion behavior of CFRP/30CrMo bolted joints under corrosive conditions was investigated based on the salt spray corrosion tests for the structural joints made of dissimilar materials. Electrochemical tests and surface morphology observations were performed on individually corroded CFRP and 30CrMo specimens to characterize their respective corrosion potential, current density, and surface morphology. Mechanical performance tests were conducted on CFRP/30CrMo single‐lap bolted joints to evaluate the structural response under varying salt spray exposure durations. After testing individual materials, CFRP and 30CrMo showed reduced corrosion resistance, with potentials shifting from 0.2 V to −0.15 V and −0.55 V to −0.85 V, and current densities rising from 10 ⁻⁷ to 10 ⁻⁵ A/cm ² and 10 ⁻⁶ to 10 ⁻⁴ A/cm ² , respectively, indicating intensified corrosion. Microstructural analysis revealed an increased amount and thickness of irregular granular deposits on 30CrMo and the emergence of a small number of pits on CFRP. Mechanical performance tests showed that, with increasing corrosion time, the joint's maximum strength dropped by about 6%, and its elastic modulus declined by approximately 48%. These findings contribute to a deeper understanding of galvanic corrosion mechanisms in hybrid joints and offer valuable guidance for the design and long‐term reliability assessment of CFRP/metal structures in marine or similarly aggressive environments.