Superior synergistic corrosion inhibition of brass in NaCl solution by 2-mercaptobenzothiazole and TiO2 nanoparticles compared with SiO2

Abstract 2-Mercaptobenzothiazole (MBT) combined with nanoparticles exhibits a synergistic corrosion inhibition effect for brass in 3.5% NaCl solution. The corrosion behavior was evaluated using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization techniques. The inhibition efficiency increased with MBT concentration (0–20 ppm), reaching 97.4% at 20 ppm. The addition of 10 ppm nanoparticles further enhanced the inhibition performance. In particular, TiO 2 nanoparticles improved the efficiency to 98.2%, showing superior performance compared with SiO 2 nanoparticles (94%). The adsorption studies showed that the Langmuir isotherm model (R² = 0.9941) was adopted by MBT, with ΔG° ads = (− 12.66 kJ mol −1 ) and K ads = 2.98 L mol −1 , indicating spontaneous adsorption dominated by physical with weak chemical interaction. Density Functional Theory (DFT) calculations at the B3LYP/LANL2DZ level were performed to study the electronic properties and adsorption behavior of MBT and its nanoparticle-modified systems. The results show that nanoparticle incorporation enhances the reactivity and adsorption characteristics of MBT. The MBT–TiO 2 system exhibits the most negative adsorption energy, smaller energy gap, and higher charge transfer ability (ΔN max ), indicating strong interaction with partial chemisorption character, while the MBT–SiO 2 system shows weaker adsorption despite higher electrophilicity. This improvement is attributed to the synergistic interaction between MBT and the incorporated nanoparticles, which enhanced the adsorption strength of inhibitor molecules onto the brass surface and promoted the formation of a highly compact protective layer through effective filling of surface pores and structural imperfections. The originality of this work is demonstrated by the fact that the electronic nature of the nanoparticles, rather than the physical barrier effect, dominates the compactness, interfacial stability and electrochemical performance of the MBT-based protective films.