Environmentally friendly Zn–Al layered double hydroxide (LDH)-based sol–gel corrosion protection coatings on AA 2024-T3

  • R. SubasriEmail author
  • K. R. C. Soma Raju
  • D. S. Reddy
  • A. Jyothirmayi
  • Vijaykumar S. Ijeri
  • Om Prakash
  • Stephen P. Gaydos


Zn–Al layered double hydroxide (LDH) intercalated with various corrosion inhibitors namely vanadate (E1), 2-mercapto benzothiazole (E3), molybdate (E7), phytic acid (E8) and 8-hydroxyquinoline (E9) was dispersed in a hybrid sol–gel silica matrix sol. Bilayer coatings with configurations E3|E1, E7|E1, E8|E1 and E9|E1 were generated on aluminum alloy AA 2024-T3 substrates using the inhibitor intercalated LDH modified sols by dip coating technique followed by UV curing and thermal curing at 80°C for 1 h in air. Corrosion resistance of coatings deposited from matrix sol with and without inhibitor intercalated LDH was studied by electrochemical impedance spectroscopy, potentiodynamic polarization after exposure to 3.5% NaCl and salt spray tests, results of which were compared with those of uncoated and chromated substrates. A non-chromated primer was applied on the sol–gel coated substrates. Adhesion of the coatings to the substrate and to the primer was evaluated by peel-off tape test and found to be rank 5. The sol–gel coated substrates did not exhibit corrosion during salt spray tests. Electrochemical tests showed that all the sol–gel coated substrates exhibited superior corrosion resistance when compared to bare and chromated substrates. More specifically, coatings generated using the corrosion inhibitors phytic acid and 8-hydroxy quinoline intercalated Zn–Al LDH were seen to render maximum corrosion protection, exhibiting two orders of magnitude lower corrosion currents than bare substrates and one order lower corrosion current than chromated substrate, after 120-h exposure to 3.5% NaCl solution.


Layered double hydroxides Corrosion Inhibitors Sol–gel coatings Hexavalent chrome Corrosion protection AA2024-T3 



The authors would like to acknowledge the constant support provided by Director, ARCI throughout the course of this investigation and research funding from Boeing. Authors would like to thank A. Ramesh, J.V. Rao, B.S. Rao, G. Venkat Rao and K.S. Rao for the technical support and G.V.R. Reddy for the SEM data acquisition.


  1. 1.
    Burakowski, T, Wierzchon, W, Surface Engineering of Metals: Principles, Equipment Technologies. CRC Press, Boca Raton (1999)Google Scholar
  2. 2.
    Koch, GH, Brongers, MP, Thompson, NG, Virmani, YP, Payer, JH, “Corrosion Costs and Preventive Strategies in the United States”. FHWA-RD-01-156, U. S. Department of Transportation, Federal Highway Administration, Washington, DC (2001)Google Scholar
  3. 3.
    Kendig, MW, Davenport, A, Isaacs, HS, “The Mechanism of Corrosion Inhibition by Chromate Conversion Coatings from X-Ray Absorption Near Edge Spectroscopy (Xanes).” Corr. Sci., 34 41–49 (1993)CrossRefGoogle Scholar
  4. 4.
    Lytle, FW, Greegor, RB, Bibbins, GL, Blohowiak, KY, Smith, RE, Truss, GD, “An Investigation of the Structure and Chemistry of a Chromium-Conversion Surface Layer on Aluminum.” Corros. Sci., 37 349–369 (1995)CrossRefGoogle Scholar
  5. 5.
    Zhao, J, Xia, L, Sehgal, A, Lu, D, McCreery, RL, Frankel, G, “Effects of Chromate and Chromate Conversion Coatings on Corrosion Of Aluminum Alloy 2024 T3.” Surf. Coat. Technol., 140 51–57 (2001)CrossRefGoogle Scholar
  6. 6.
    Xia, L, Akiyama, E, Frankel, G, McCreery, RL, “Storage and Release of Soluble Hexavalent Chromium from Chromate Conversion Coatings Equilibrium Aspects of Cr+4 Concentration.” J. Electrochem. Soc., 147 2556–2562 (2000)CrossRefGoogle Scholar
  7. 7.
    Kulinich, SA, Akhtar, AS, “On Conversion Coating Treatments to Replace Chromating for Al Alloy: Recent Developments and Possible Future Directions.” Russ. J. Non-ferrous Metals., 53 176–203 (2012)CrossRefGoogle Scholar
  8. 8.
    Droniou, P, Fristad, WE, Liang, JL, “Nanoceramic-Based Conversion Coating: Ecological and Economic Benefits Position Process as a Viable Alternative to Phosphating Systems.” Met. Finish, 103 41–43 (2005)CrossRefGoogle Scholar
  9. 9.
    Wang, D, Bierwagen, GP, “Review: “Sol–Gel Coatings on Metals for Corrosion Protection.” Prog. Org. Coat., 64 327–338 (2008)CrossRefGoogle Scholar
  10. 10.
    Zheludkevich, ML, Salvado, IM, Ferreira, MGS, “Sol–Gel Coatings for Corrosion Protection of Metals.” J. Mater. Chem., 15 5099–5111 (2005)CrossRefGoogle Scholar
  11. 11.
    Duran, A, Castro, Y, Aparicio, M, Conder, A, Damborenea, JJ, “Protection and Surface Modification of Metals with Sol–Gel Coatings.” Int. Mater. Rev., 52 175–190 (2007)CrossRefGoogle Scholar
  12. 12.
    Conde, A, Durán, A, Damborenea, JJ, “Polymeric Sol–Gel Coatings as Protective Layers of Aluminium Alloys.” Prog. Org. Coat., 464 288–296 (2003)CrossRefGoogle Scholar
  13. 13.
    Rosero-Navarro, NC, Curioni, M, Bingham, R, Durán, A, Aparicio, M, Cottis, RA, Thompson, GE, “Electrochemical Techniques for Practical Evaluation of Corrosion Inhibitor Effectiveness. Performance of Cerium Nitrate as Corrosion Inhibitor for AA2024T3 Alloy.” Corros. Sci., 52 (10) 3356–3366 (2010)CrossRefGoogle Scholar
  14. 14.
    Pellice, S, Galliano, P, Castro, Y, Durán, A, “Hybrid Sol–Gel Coatings Produced from TEOS and γ-MPS.” J. Sol–Gel Sci. Technol., 28 81–86 (2003)CrossRefGoogle Scholar
  15. 15.
    Shchukin, DG, Zheludkevich, ML, Yasakau, K, Lamaka, S, Ferreira, MGS, Möhwald, H, “Layer-by-Layer Assembled Nanocontainers for Self-Healing Corrosion Protection.” Adv. Mater., 18 1672–1678 (2006)CrossRefGoogle Scholar
  16. 16.
    Skorb, EV, Fix, D, Andreeva, DV, Mohwald, H, Shchukin, DG, “Surface-Modified Mesoporous SiO2 Containers for Corrosion Protection.” Adv. Funct. Mater., 19 2373–2379 (2009)CrossRefGoogle Scholar
  17. 17.
    Tedim, J, Poznyak, SK, Kuznetsova, A, Raps, D, Hack, T, Zheludkevich, ML, Ferreira, MGS, “Enhancement of Active Corrosion Protection via Combination of Inhibitor-Loaded Nanocontainers.” ACS Appl. Mater. Interfaces, 2 1528–1535 (2010)CrossRefGoogle Scholar
  18. 18.
    Mishra, T, Mohanty, AK, Tiwari, SK, “Recent Development in Clay Based Functional Coating for Corrosion Protection.” Key Eng. Mater., 571 93–109 (2013)CrossRefGoogle Scholar
  19. 19.
    Lvov, YM, Shchukin, DG, Mohwald, H, Price, R, “Halloysite Clay Nanotubes for Controlled Release of Protective Agents.” ACS Nano, 2 814–820 (2008)CrossRefGoogle Scholar
  20. 20.
    Joshi, A, Abdullayev, E, Vasiliev, A, Volkova, O, Lvov, Y, “Interfacial Modification of Clay Nanotubes for the Sustained Release of Corrosion Inhibitors.” Langmuir, 29 7439–7448 (2013)CrossRefGoogle Scholar
  21. 21.
    Abdullayev, E, Price, R, Shchukin, D, Lvov, Y, “Halloysite Tubes as Nanocontainers for Anticorrosion Coating with Benzotriazole.” ACS Appl. Mater. Interfaces, 1 1437–1443 (2009)CrossRefGoogle Scholar
  22. 22.
    Lanzara, G, Yoon, Y, Liu, H, Peng, S, Lee, WI, “Carbon Nanotube Reservoirs for Self-Healing Materials.” Nanotechnology, 20 335704–335711 (2009)CrossRefGoogle Scholar
  23. 23.
    Jung, IK, Gurav, JL, Bangi, UKH, Baek, S, Park, HH, “Silica Xerogel Films Hybridized with Carbon Nanotubes by Single Step Sol–Gel Processing.” J. Non-Cryst. Solids, 358 550–556 (2012)CrossRefGoogle Scholar
  24. 24.
    Zheludkevich, ML, Poznyak, SK, Rodrigues, LM, Raps, D, Hack, T, Dick, LF, Nunes, T, Ferreira, MGS, “Active Protection Coatings with Layered Double Hydroxide Nanocontainers of Corrosion Inhibitor.” Corros. Sci., 52 602–611 (2010)CrossRefGoogle Scholar
  25. 25.
    Tedim, J, Zheludkevich, ML, Salak, AN, Lisenkov, A, Ferreira, MGS, “Nanostructured LDH-Container Layer with Active Protection Functionality.” J. Mater. Chem., 21 15464–15470 (2011)CrossRefGoogle Scholar
  26. 26.
    Stimpfling, T, Leroux, F, Hintze-Bruenning, H, “Organo-Modified Layered Double Hydroxide in Coating Formulation to Protect AA 2024 from Corrosion.” Colloids Surf. A, 458 147–154 (2014)CrossRefGoogle Scholar
  27. 27.
    Harvey, TG, “Cerium-Based Conversion Coatings on Aluminium Alloys: A Process Review.” Corros. Eng Sci Technol., 48 248–269 (2013)CrossRefGoogle Scholar
  28. 28.
    Salak, AN, Tedim, J, Kuznetsova, AI, Zheludkevich, ML, Ferreira, MGS, “Anion Exchange in Zn–Al Layered Double Hydroxides: In Situ X-Ray Diffraction Study.” Chem. Phys. Lett., 495 73–76 (2010)CrossRefGoogle Scholar
  29. 29.
    Dong, Y, Wang, F, Zhou, Q, “Protective Behaviours of 2-Mercaptobenzothiazole Intercalated Zn–Al-Layered Double Hydroxide Coating.” J. Coat. Technol. Res., 11 (5) 793–803 (2014)CrossRefGoogle Scholar
  30. 30.
    Zheludkevich, ML, Poznyak, SK, Rodrigues, LM, Raps, D, Hack, T, Dick, LF, Nunes, T, Ferreira, MGS, “Active Protection Coatings with Layered Double Hydroxide Nanocontainers of Corrosion Inhibitor.” Corros. Sci., 52 602–611 (2010)CrossRefGoogle Scholar
  31. 31.
    Wang, Y, Zhang, D, “Synthesis, Characterization and Controlled Release Anticorrosion Behavior of Benzoate Intercalated Zn–Al Layered Double Hydroxides.” Mater. Res. Bull., 46 1963–1968 (2011)CrossRefGoogle Scholar
  32. 32.
    Liu, J, Zhang, Y, Yu, M, Li, S, Xue, B, Yin, X, “Influence of Embedded ZnAlCe–NO3 Layered Double Hydroxides on the Anticorrosion Properties of Sol–Gel Coatings for Aluminum Alloy.” Progr. Org. Coat., 81 93–100 (2015)CrossRefGoogle Scholar
  33. 33.
    Shi, H, Han, EH, Liu, F, Kallip, S, “Protection of 2024-T3 Aluminium Alloy by Corrosion Resistant Phytic Acid Conversion Coating.” Appl. Surf. Sci., 280 325–331 (2013)CrossRefGoogle Scholar
  34. 34.
    Gao, HF, Zhang, ST, Liu, CL, Xu, JQ, Li, J, “Phytic Acid Conversion Coating on AZ31B Magnesium Alloy.” Surf. Eng., 28 387–392 (2012)CrossRefGoogle Scholar
  35. 35.
    Zhong, Y, Yingjun, Z, Jingwei, D, Qingsong, Y, Yawei, S, Yanqiu, W, Guozhe, M, “Effect of Phytic Acid on Corrosion Performance of Epoxy Coating on Rust Q235 Carbon Steel.” Corros. Sci. Prot. Technol., 27 183–187 (2015)Google Scholar
  36. 36.
    Chou, TP, Chandrasekaran, C, Cao, GZ, “Sol–Gel Derived Hybrid Coatings for Corrosion Protection.” J. Sol-Gel Sci. Technol., 26 321–327 (2003)CrossRefGoogle Scholar
  37. 37.
    Chou, TP, Chandrasekaran, C, Limmer, SJ, Nguyen, C, Cao, GZ, “Organic–Inorganic Sol–Gel Coating for Corrosion Protection of Stainless Steel.” J. Mater. Sci. Lett., 21 251–255 (2002)CrossRefGoogle Scholar
  38. 38.
    Chou, TP, Chandrasekaran, C, Limmer, SJ, Seraji, S, Wu, Y, Forbess, MJ, Nguyen, C, Cao, GZ, “Organic–Inorganic Hybrid Coatings for Corrosion Protection.” J. Non-Cryst. Solids, 290 153–162 (2001)CrossRefGoogle Scholar

Copyright information

© American Coatings Association 2019

Authors and Affiliations

  • R. Subasri
    • 1
    Email author
  • K. R. C. Soma Raju
    • 1
  • D. S. Reddy
    • 1
  • A. Jyothirmayi
    • 2
  • Vijaykumar S. Ijeri
    • 3
  • Om Prakash
    • 3
  • Stephen P. Gaydos
    • 4
  1. 1.Centre for Sol–Gel CoatingsInternational Advanced Research Centre for Powder Metallurgy and New Materials (ARCI)Balapur, HyderabadIndia
  2. 2.Centre for Materials Characterization and TestingInternational Advanced Research Centre for Powder Metallurgy and New Materials (ARCI)Balapur, HyderabadIndia
  3. 3.Boeing Research and Technology - India, MMT LabBangaloreIndia
  4. 4.Boeing Research and TechnologySt. LouisUSA

Personalised recommendations