Epoxy/alumina composite coating on welded steel 316L with excellent wear and anticorrosion properties

Robust corrosion guard, mechanical and UV aging properties of metal complex/epoxy hybrid composite coating for C-steel applications

Incorporation of novel-prepared metal–organic complexes as crosslinking accelerators for multifunctional epoxy was on top of interest by coating formulators. The present work investigated the loading of mixed ligand metal complexes (Zr(IV) and Cu(II)) of metformin (MF) and 2.2′bipyridine (Bipy) against the free ligands as crosslinking modifiers via some epoxy coating formulations to assess their superb performances on the C-steel surface. Zr(IV) and Cu(II) demonstrated the minor energy gap (∆E) values at 0.190 au compared to free MF and Bipy according to the calculated energy values, and this behavior reflected their enhanced properties via epoxy coating applications. EIS measurements using high saline formation water as a corrosive medium were performed and offered that PA-DGEBA/MC-Cu coated film showed the superior resistance values (R_ct = 940 and R_c = 930 kΩ cm²). The accelerated corrosion salt spray experiment clarified that PA-DGEBA/MC-Cu coating achieved the least corrosion rate at 0.00049 mm/y and exhibited the highest protection efficiency of 99.84%. SEM/EDX combination survey affirmed the protective performance of the checked coatings. AFM microanalysis confirmed that surface-treated Cu(II) coating displayed the smoothest film surface with complete curing. Mechanical durability properties were evaluated and the obtained results illustrated that pull-off adhesion for PA-DGEBA/MC-Cu coated film fulfilled the highest adhesion strength at 6.3 MPa, the best bend character at 77, and the maximum impact resistance at 59.7 J. UV immovability trial was performed at 10 irradiance and 80 h duration. PA-DGEBA/MC-Cu coated film displayed the highest resistance to UV irradiance with blistering (#8 size and few frequencies) in addition to offering a minor gloss variation and matt properties.

Synthesis of TiO2 nanogel composite for highly efficient self-healing epoxy coating

INTRODUCTION

Organic coatings are the most effective and facile methods of protecting steel against corrosion, which shields it from direct contact with oxygen and moisture. However, they are inherently defective and susceptible to damage, which allows the penetration of the corrosive media into the underlying substrates. Self-healing coatings were developed to address this shortcoming.

OBJECTIVE

The current research aims to develop a coating with superior self-healing ability via embedment of titanium dioxide (TiO₂) nanogel composite (NC) in a commercial epoxy.

METHODS

The TiO₂ NC was prepared by efficient dispersion of TiO₂ nanoparticles in copolymer gel of acrylamide (AAm) and 2-acrylamido-2-methyl propane sulfonic acid (AMPS) with the help of 3-(trimethoxysilyl) propyl methacrylate (MPS). The chemical structure, morphology, and thermal properties of the modified and functionalized nanoparticles were assessed by infrared spectroscopy, electron microscopy, X-ray diffraction, and thermogravimetric analysis, respectively. In addition, TiO₂ nanoparticles, nano-TiO₂ functionalized monomer (NTFM), and NTFM/AAm/AMPS in different weight percentages were incorporated into epoxy resin to prepare a self-healing coating.

RESULTS

The results confirmed the successful fabrication of the NC. In addition, the incorporation of 1 wt% NTFM/AAm/AMPS led to homogenous dispersion, enhanced anti-corrosive and self-healing performance with the healing efficiencies of 100% and 98%, which were determined by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods, respectively.

CONCLUSION

The prepared NC was sensitive towards salt concentration, pH, which aids the quick reaction of the TiO₂ NC to corrosive ions, once the cracks occur. In addition, this is a unique feature compared to the other self-healing mechanisms, especially, the encapsulation of healing agents, which can be effective as long as the healing agent is present.