Integrating Time-of-Wetness and Electrochemical Methods to Predict Atmospheric Galvanic Corrosion of Aluminum Alloys

Atmospheric galvanic corrosion of aluminum alloys continues to challenge accurate prediction and mitigation, particularly in mixed-material systems used in aerospace and marine environments. This includes systems exposed to dynamic atmospheric conditions where wet–dry cycling, chloride deposition, and microstructural heterogeneity govern degradation processes. Aluminum alloys, valued for their strength-to-weight ratio and passivity, are particularly susceptible to localized and galvanic attack when combined with dissimilar materials in aerospace, marine, and energy infrastructure.

Conventional salt-spray or cyclic corrosion tests fail to replicate the complex wet–dry cycling and localized electrochemical interactions that govern long-term atmospheric degradation. This study explores how to integrate a hybrid framework combining accelerated laboratory electrochemical techniques with time-of-wetness (TOW) to better predict the atmospheric galvanic behavior of 6061-T6 aluminum (UNS A96061) coupled with stainless steel (UNS S30400), copper (UNS C11000), and carbon-fiber reinforced polymer composites (CFR PMC).

Zero-resistance ammeter (ZRA) experiments were performed in a controlled-humidity chamber and a cyclic-corrosion test chamber under varying chloride concentrations to simulate different atmospheric exposures. The galvanic current data were correlated with modified Faraday-based equations incorporating measured TOW to estimate corrosion rates in g m⁻² day⁻¹. The aluminum–copper couple exhibited the highest current densities and corrosion rates (up to 12 g m⁻² day⁻¹) under high-chloride conditions, while aluminum–CFR PMC and aluminum–stainless-steel couples showed comparable but lower rates. The integrated approach successfully bridged the gap between accelerated tests and real atmospheric behavior by quantifying the effects of wet/dry cycles on galvanic kinetics.

The findings highlight the potential of TOW-based electrochemical modeling as a predictive tool for assessing material compatibility and optimizing design in dissimilar-metal assemblies. Future work includes more cyclic corrosion chamber testing and outdoor validation at various exposure sites to refine the correlation between laboratory and field data.