Inclusion of 5-Mercapto-1-Phenyl-Tetrazole into β-Cyclodextrin for Entrapment in Silane Coatings: An Improvement in Bronze Corrosion Protection

Abstract

The corrosion protection of coatings can be reinforced by the addition of entrapped corrosion inhibitors. β-cyclodextrin (β-CD) can form inclusion complexes with small inhibiting organic molecules that, when entrapped in coatings, allow the inhibitor release and adsorption at corrosion initiation sites. In this paper, several Nuclear Magnetic Resonance (NMR)-based experiments (e.g., Complexation-Induced Shifts (CIS), NMR titration, Diffusion-Ordered Spectroscopy (DOSY)) were performed to study the stability and geometry of a complex formed by β-cyclodextrin with 5-mercapto-1-phenyl-tetrazole (MPT). The complex was also detected by Electrospray Ionization (ESI) mass spectrometry and characterized by Fourier Transform Infrared (FTIR) spectra. Its influence on the protectiveness of a silane coating against bronze corrosion was evaluated in plain (AR) and concentrated (ARX10) synthetic acid rain, under different exposure conditions. In particular, the time evolution of the polarization resistance values during 20 days in ARX10 and the polarization curves recorded at the end of the immersions evidenced a higher protectiveness of the coating with the β-CD–MPT complex in comparison to that containing only MPT or only β-CD. The cyclic AR spray test carried out on coated bronze coupons with cross-cut scratches evidenced the absence of underfilm corrosion starting from the scratches only in the complex-containing coating.

β-Cyclodextrin Inclusion Complex Containing Litsea cubeba Essential Oil: Preparation, Optimization, Physicochemical, and Antifungal Characterization

“…β-cyclodextrin (β-CD), belongs to the family member of cyclic oligosaccharides [17], which has a central hydrophobic inner cavity and an outward hydrophilic surface, and it has strong complexing capacity towards small molecules [18]. β-CD commonly served as a microcapsule coating material [19].…”

Ultrasonic Sensors-Assisted Corrosion Studies on Surface Coated AlSi9Cu3 Alloy Die Castings

“…The acrylic paint ED coatings exhibited higher resistance in AC and lowered resistance in DC; on the other hand, other coatings exhibited lower resistance in AC and higher resistance in DC. In future work, advanced digital-driven transformation technologies (Industry X.0), including artificial intelligence approaches, shall be deployed for overcoming the challenges faced due to corrosion and related issues [25][26][27][28][29][30][31][32][33][34][35][36], thereby improving the quality of the coating longevity. The salt spray test results confirm that 3-coat polyester with epoxy primer coated sample exhibits an oxide film on the surface that temporarily resist the local corrosion attack.…”

Application of polymer corrosion inhibitors in metal corrosion control: a review

“…Incorporation of an encapsulated corrosion inhibitor in β-CD allows the inhibitor to be released and adsorbed at the corrosion initiation site. Monticelli et al (2019) investigated the effect of complexes formed by β-CD and 5-mercapto-1-phenyltetrazolium (MPT) on the corrosion protection properties of silane coatings on bronze in normal and concentrated synthetic acid rain. The temporal evolution of the polarization resistance values in concentrated synthetic acid rain for 20 days and the polarization curves recorded at the end of the immersion showed that the coatings containing the β-CD-MPT complex provided higher protection compared to coatings containing only MPT or only β-CD.…”