resumo
2-mercaptobenzothiazole (MBT) and 1,2,3-benzotriazole (BTA) are very promising inhibitors for the corrosion protection of aluminum alloys. These inhibitors can be incorporated in protective coatings in the form of anions intercalated into interlayers of layered double hydroxides (LDHs). Capacity and performance of such LDH-nanocontainers depend on the arrangement of the anions in their interlayers. In this work, intercalation of MBT- and BTA(-) into Mg-Al-NO3 and Zn-Al-NO3 LDHs were studied in detail using X-ray diffraction (XRD) methods including in situ XRD. The nitrate-to-MBT(BTA) anion exchange is much faster than considered previously. Well-formed Mg-Al-MET, Zn-Al-MBT, Mg-Al-ETA LDHs were obtained after a 20-min exchange reaction at pH 11.5 at room temperature. It was demonstrated that Zn-Al-BTA LDH cannot be obtained under the same conditions due to the reaction between BTA and the Zn-Al hydroxide layers. Substitution of nitrates by organic anions occurs with the participation of hydroxide anions. Although no intermediate LDH phase intercalated with the combination of NO3- and OH- appears, formation of the LDH-MBT and LDH-BTA phases results also in appearance of an LDH phase intercalated with OH- at the final stage of the anion exchange. In the LDH interlayer, MBT- and BTA(-) form a double layer in which these species have a tilted orientation against the layer plane (herringbone like arrangement). Such an arrangement meets the LDH layer-interlayer electroneutrality and matches well with the observed values of the layer-interlayer distance. (C) 2015 Elsevier Inc. All rights reserved.
palavras-chave
ACTIVE CORROSION PROTECTION; HYDROTALCITE-LIKE MINERALS; POLYTYPE DIVERSITY; ALUMINUM-ALLOY; EXCHANGE; INHIBITION; ASSEMBLIES; COATINGS; MICRO; ZINC
categoria
Chemistry
autores
Serdechnova, M; Salak, AN; Barbosa, FS; Vieira, DEL; Tedim, J; Zheludkevich, ML; Ferreira, MGS
nossos autores
Andrei Salak
Investigador Principal
Daniel Eduardo Loureiro Vieira
Estudante de doutoramento
João Tedim
Professor associado
Maria Serdechnova
Bolseiro de pós-Doutoramento
Mário Guerreiro Silva Ferreira
Professor(a) Jubilado(a)
Mikhail Zheludkevich
Investigador Principal ConvidadoGrupos
G2 - Materiais Fotónicos, Eletrónicos e Magnéticos
G3 - Materiais Eletroquímicos, Interfaces e Revestimentos
Projectos
PROAIR - Active PROtection of multi-material assemblies for AIRcrafts (PROAIR)
FUNACOP - Nanomateriais para aplicação em revestimentos funcionais (FUNACOP)
MULTI-functional metallic SURFaces via active Layered Double Hydroxide treatments (MULTISURF)
agradecimentos
The authors thank Dr. T. Galvao for assistance in anion-exchange experiments. This work was partially supported by MULTISURF (Marie Sklodowska-Curie grant agreement No. 645676) and PROAIR (grant agreement No 612415) European projects. This work was also funded by ERDF Funds through Operational Competitiveness Program - COMPETE in the frame of the project FUNACOP - FCOMP-01-0124-FEDER- 38777. JT thanks Fundacao para a Ciencia e Tecnologia (Portugal) for researcher Grant IF/00347/2013.