Smart Coating Embedded with pH-Responsive Nanocapsules Containing a Corrosion Inhibiting Agent

Area of Science:

• Materials Science
• Corrosion Engineering
• Nanotechnology

Background:

• Aluminum alloy 3003 is susceptible to corrosion, necessitating effective protective coatings.
• Traditional corrosion inhibitors can have limited longevity and controlled release mechanisms.

Purpose of the Study:

• To develop and evaluate an epoxy coating incorporating nanocapsules of Triethanolamine (TEA) for enhanced, long-term corrosion protection of aluminum alloy 3003.
• To investigate the mechanism of corrosion inhibition and the release behavior of TEA from nanocapsules within the epoxy matrix.

Main Methods:

• Encapsulation of Triethanolamine (TEA) via free-radical polymerization.
• Embedding TEA nanocapsules (450 nm average size) into an epoxy coating at 10 wt %.
• Corrosion evaluation using Electrochemical Impedance Spectroscopy (EIS), Scanning Vibrating Electrode Technique (SVET), optical microscopy, Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray Spectroscopy (EDS).
• Nuclear Magnetic Resonance (NMR) spectroscopy to confirm TEA release.

Main Results:

• The epoxy coating with 10 wt % TEA nanocapsules achieved over 85% inhibition efficiency in early-stage mild corrosion.
• TEA release was triggered by local pH changes, forming an inhibiting layer and enabling spontaneous surface repassivation.
• SVET showed significantly lower current density on coated surfaces compared to controls.
• SEM and EDS confirmed reduced staining and suppressed oxidation on protected aluminum surfaces after 60 days.
• NMR spectra confirmed sustained TEA release throughout the testing period.

Conclusions:

• Encapsulated TEA in epoxy coatings provides effective and long-term corrosion protection for aluminum alloy 3003.
• The localized pH change-triggered release mechanism ensures efficient and sustained inhibition.
• This nanotechnology approach offers a promising strategy for advanced anti-corrosion coatings.