Electrochemical insights: octadecanethiol self-assembled monolayers on leaded brass for enhanced anti-corrosion protection in non-complexing media—unraveling the impact of halide ions

This paper presents a comprehensive study of the electrochemical and anticorrosion properties of leaded α,β'-brass (CuZn39Pb3), both in its bare form and coated with an octadecanethiol self-assembled monolayer (ODT SAM). The study was conducted in a non-complexing ClO₄^– solution at pH3, with and without halide ions. The results demonstrate that CuZn39Pb3 exhibits good resistance to dissolution compared to lead-free diphasic brass (Cu40Zn). It is observed that the exposure time to the corrosive solution and the concentration of different halide species strongly influence the dissolution of CuZn39Pb3. The formation of ODT SAMs on CuZn39Pb3 was characterized using various techniques, and optimal conditions to obtain a compact monolayer were determined. The data show that ODT SAMs effectively suppress the selective dissolution of CuZn39Pb3 alloy. Both Tafel polarization curves and electrochemical impedance spectroscopy (EIS) results are in good agreement and demonstrate the high ability of ODT SAMs to protect the alloy against corrosion, even in the presence of halide species. Under our conditions, the ODT film primarily acts as a cathodic inhibitor and behaves as a mixed inhibitor type. Notably, F‾ ions have a minimal effect on the dezincification of the CuZn39Pb3 alloy. Inductively coupled plasma spectroscopy (ICPS) and scanning electron microscopy (SEM) results confirm the high efficiency of ODT-SAMs in preventing the corrosion of the CuZn39Pb3 alloy. This is attributed to the formation of a compact ODT layer network, which stabilizes the alloy surface and impedes the infiltration of corrosive species and water to the substrate surface.