Galvanic corrosion between zinc and carbon steel investigated by local electrochemical impedance spectroscopy

The study of galvanic coupling between two metals is still a relevant topic, particularly in aerospace and automotive industries. The development of local electrochemical techniques leads to a better understanding of the phenomena occurring at the interfacial zone. Galvanic coupling between carbon steel and zinc was investigated by local electrochemical impedance spectroscopy (LEIS) in a 0.06 g L−1 NaCl solution. Voltammetry and conventional electrochemical impedance experiments were also performed to better analyze the local impedance data. Local measurements carried out at a fixed frequency showed that zinc dissolution was more significant at the steel/zinc interface. A particular shape of the local impedance diagram was observed above the zinc surface with the presence of a large inductive loop in the low-frequency range. Numerical simulations, performed by using finite element method, allowed the local experimental diagrams obtained over the zinc sample to be validated taking into account the radial contribution of the current between both materials in galvanic coupling.

► The galvanic coupling of zinc–steel was highlighted by EIS and LEIS.
► LEIS showed the contribution of the radial component of the current.
► The current distribution was stronger at the metals interface.
► Simulation was in accordance with LEIS diagrams in galvanic corrosion.