Pre-treatment of Carbon Steel with Hybrid Film Modified with Different Natural Inhibitors (Garlic and Cocoa)

One way to protect carbon steel from corrosion is through pre-treatment and corrosion inhibitors, such as the use of silane layers that can protect against corrosion. In this study, the corrosion resistance of the TEOS/GPTMS (Tetraethyl orthosilicate / 3-Glycidoxypropyltrimethoxysilane) hybrid film modified with garlic peel powder or cocoa shell powder on carbon steel was evaluated. By electrochemical impedance spectroscopy (EIS) it was observed that the incorporation of inhibitors promoted higher values of impedance modulus compared to the bare metal substrate or in absence of inhibitor, and the concentration of 1.77 g L−1 provided the best performance for both natural inhibitors. The Fourier transform infrared spectroscopy (FTIR) showed that the addition of inhibitors to the hybrid film promoted a better hydrolysis in the formation of the films. By the Scanning Electron Microscopy and Energy Dispersive Spectroscopy (SEM/EDS) it was noted that there was the formation of the hybrid film on the metal surface, and the insertion of the inhibitor to the silane film enabled the formation of grains that precipitate from the deposition of the inhibitor on the substrate surface. The Scanning Vibrating Electrode Technique (SVET) shows that the inhibitors improved corrosion resistance of the hybrid film, corroborating with the EIS analysis. The contact angle shows that the presence of the inhibitor in the silane film makes it less hydrophilic. The roughness profile shows that the hybrid film with cocoa has the highest roughness represented by a higher average value of Average Roughness (Rz).