To modify the corrosion protection provided by conversion coated Zn-Al-CO3 layered double hydroxides (LDHs) on electrogalvanized steel sheets (EG steels), methods to intercalate NO3 − during post treatment were explored and the effect of intercalation on corrosion resistance was evaluated. EG steels were immersed in a Na2Al2O4 based solution to form a Zn-Al-CO3 LDH conversion coating layer, and were then immersed in a NaNO3 methanol solvent to intercalate NO3 −. After 2 h of immersion, it was found that NO3 − had completely exchanged with the originally intercalated CO3 2− anions in the conversion coated Zn-Al-CO3 LDHs. Corrosion resistance measurements of the EG steel surfaces protected by the NO3 − intercalated in the LDH layer were performed by a simple immersion test and a droplet test. When the samples were immersed in a large amount of 0.1 M NaCl, the corrosion resistance of the NO3 − intercalated LDH layer was inferior to that of the control sample. In contrast, the samples that were exposed to a 100 μl droplet of 0.1 M NaCl displayed improved corrosion resistance. The difference in these results was attributed to the solubility of the LDH layer and the resulting effect on the release process of NO3 − from the LDH layer.
|Journal||Journal of the Electrochemical Society|
|State||Published - 2018|
Bibliographical noteFunding Information:
The authors thank Prof. Belinda Hurley and Prof. Gerald S. Frankel for their discussion of this work and help with grammatical editing. We also wish to acknowledge financial support received from JFE Steel Corporation, Japan.
© The Author(s) 2018.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry