Smart containers can be produced with polyelectrolyte multilayers that can release inhibitors in response to environmental changes at the coating defects. In this study, mesoporous TiO 2 hollow spheres were adopted as carriers for the encapsulation of corrosion inhibitor. The inhibitor-loaded TiO 2 containers were modified by polyelectrolyte shells using layer-by-layer self-assembly technology. The release behaviour of the encapsulated inhibitor was investigated using UV-visible spectroscopy. Corrosion protection performance of the epoxy coating with polyelectrolyte-modified TiO 2 containers was studied using electrochemical impedance spectroscopy and scanning Kelvin probe (SKP) techniques. Epoxy coating with the polyelectrolyte-modified TiO 2 containers provided better barrier properties than that of the blank coating. Waterborne epoxy coating impregnated with the polyelectrolyte-modified TiO 2 containers presented a significant self-healing effect after immersion in 0.5 M NaCl solution from the SKP results.

In the present work, polyaniline (PANI) modified attapulgite (ATP) nanocomposite was synthesized and employed as reinforcements to enhance the corrosion resistance of the alkyd coating. The morphological and structural properties of the synthesized ATP/PANI were characterized by transmission scanning electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Electrochemical impedance spectroscopy (EIS) was employed to investigate the corrosion protection performance of the alkyd coatings, showing the improved corrosion resistance in the presence of the ATP/PANI nanocomposite. Scanning Kelvin probe (SKP) and Raman spectroscopy were performed to characterize the metal passivation inhibition ability of composite coatings. Compared with blank coating, the SKP results revealed a clear decrease in electrochemical activity at the scratch of ATP/PANI coating. Results from Raman spectrum indicated that the protective capability of the scratched coating can be recovered through the passivation of polyaniline to form stable oxide film (Fe 2 O 3 ) on metal surface.

In this work, the corrosion behavior of high-strength low alloy (HSLA) steel welded joints in natural seawater solution was investigated by electrochemical and immersion tests. The experimental results prove that the corrosion resistance of the weld metal (WM) was higher than that of the base metal (BM). The scanning Kelvin probe results show that the potential distribution of the BM zone is lower than the heat-affected zone (HAZ) and WM zone. The scanning vibrating electrode technique results demonstrate that the initial attack for the HSLA welded joint majorly took place in the BM zone after immersion in natural seawater. The corrosion morphology of the HSLA welded joint after immersion was observed by scanning electron microscope. The corrosion morphology of BM and HAZ regions tends to be uniform corrosion, whereas it is mainly pitting corrosion for the WM zone.

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