In situ grown gluconate-containing CaAl-LDH/organic coating for steel corrosion protection

abstract

This study reports the development of anticorrosive bilayer coatings consisting of in situ grown layered double hydroxides (LDH) covered with a polyurethane layer on a steel substrate. This design aims at providing corrosion protection via the controlled release of gluconate from LDH near the substrate, while at the same time contributing to the improvement of the polyurethane layer coating adhesion. The CaAl-LDH thin film was initially grown directly on AISI 1080/1010 carbon steel and modified with environmentally friendly gluconate molecules through an ion-exchange reaction. The effect of polyurethane treatments on the LDHs thin film was systematically explored: gluconate is either intercalated in LDHs or dispersed in polyurethane coatings, and the two systems are studied to understand the role of inhibitors in bilayer coating systems at defined conditions. The structural characteristics of the developed coatings were evaluated by scanning electrochemical microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (ATR-FTIR), and glow discharge optical microscopy (GDOES). The findings of electrochemical impedance spectroscopy (EIS) measurements on coated carbon steel substrates in NaCl solution demonstrated the significance of the bilayer film design for long-term corrosion protection, by combining active corrosion protection provided by the LDH conversion film with the passive barrier effect against electrolyte species rendered by the organic polyurethane layer. Additionally, improving the polyurethane coating's wet adhesion to the substrate when applied onto CaAl-LDH opens new directions toward the co-development of surface treatments with organic coatings.

keywords

MESOPOROUS SILICA NANOCONTAINERS; CONVERSION FILMS; ZINC PHOSPHATE; EPOXY COATINGS; CARBON-STEEL; MILD-STEEL; PERFORMANCE; INHIBITION

subject category

Chemistry; Materials Science

authors

Iqbal, MA; Neves, C; Starykevich, M; Martins, R; Ferreira, MGS; Tedim, J

Groups

G3 - Electrochemical Materials, Interfaces and Coatings

Projects

Towards a new generation of sustainable nano-based additives for maritime anti-corrosion smart coatings: a multidisciplinary framework within the Atlantic (NANOGREEN)

Eco-friendly corrosion protective coatings based on smart nanotechnology platforms for a circular economy (COAT4LIFE)

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

acknowledgements

The present work was carried out in the framework of the NANOGREEN project (CIRCNA/BRB/0291/2019) funded by national funds (OE) through FCT (Fundacao para a Ciencia e a Tecnologia, I.P.), as well as the COAT4LIFE project funded by the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 101007430. Roberto Martins is funded by national funds (OE), through FCT (grant 2021.00386.CEECIND). We also acknowledge the financial support to CICECO (UIDB/50011/2020,UIDP/50011/2020 & LA/P/0006/2020) and to CESAM (UIDP/50017/2020 + UIDB/50017/2020 + LA/P/0094/2020) and by FCT/MCTES through national funds