To improve the corrosion resistance of GO/PANI/BTA/EP coating on the surface of 6061 aluminum alloy and explore its corrosion inhibition mechanism,graphene oxide (GO)/polyaniline (PANI) nanoparticles were prepared by in-situ copolymerization method. The corrosion inhibitor benzotriazole (BTA) was adsorbed on the surface of GO/PANI nanoparticles through physical adsorption, resulting in GO/PANI/BTA.The infrared spectrum shows that a layer of BTA has been successfully loaded onto the surface of GO/PANI. The adsorption rate of the loaded BTA on the surface of GO/PANI can reach 18.36%, and the release rate after 5 hours can reach over 90%, providing effective protection for aluminum alloys. The polarization curve and immersion experiment results show that the epoxy coating (GO/PANI/BTA/EP) with 1% GO/PANI/BTA added has excellent corrosion resistance. The self corrosion potential of 1% GO/PANI/BTA/EP is -0.267 V, which is 0.247 V higher than that of GO/PANI/EP; The self corrosion current density is 9.795×10-9A∙cm-2, higher than GO/PANI/EP (self corrosion current density of 7.638×10-7A∙cm-2) is two orders of magnitude lower. The 1% GO/PANI/BTA/EP composite coating has excellent corrosion resistance, and its corrosion inhibition mechanism comes from the organic combination of graphene oxide shielding, polyaniline passivation, and BTA corrosion inhibition, achieving a synergistic effect.
首先,在GO表面接枝氨基。①通过超声振动将1.0 g GO和1.08 g间苯二胺分散在250 mL蒸馏水中。②将0.70 g NaNO2加入上述混合物中,在冰水混合物中反应,用去离子水洗涤和过滤。③在真空冷冻干燥机中干燥获得GO-NH2。
然后,通过原位共聚将PANI接枝到GO-NH2表面。①将0.4 g GO-NH2和3 mL苯胺加入250 mL蒸馏水中。②将7.2 g过硫酸铵缓慢加入到上述溶液中,并将混合物在0 ℃下磁力搅拌4~5 h,直到获得深绿色产物。③用去离子水和乙醇反复洗涤数次,在80 ℃烘箱中干燥5~6 h,得到GO/PANI。
最后,将BTA负载于GO/PANI表面。①向烧瓶中加入8 g BTA和200 mL蒸馏水,加热至40 ℃,得到4%BTA水溶液。②在连续搅拌下将6 g GO/PANI加入烧瓶中,并通过真空泵施加真空24 h,以获得GO/PANI/BTA固体。③过滤固体,用乙醇反复洗涤,并在60 ℃的真空烘箱中干燥6 h,得到GO/PANI/BTA。
当涂层受损时,GO/PANI表面负载的BTA溶于水,通过间隙通道迁移至6061铝合金基体表面,与Al3+形成配合物[BTA-Al-BTA] n,沉积在涂层受损区域,防止腐蚀介质进一步扩散。同时,BTA在涂层未损伤区域的基材上形成一层薄薄的保护膜,防止腐蚀破坏[31]。配合物[BTA-Al-BTA] n 的分子结构如图9所示,其形成机理如式(1)(2)所示。由式(2)可以看出,配合物[BTA-Al-BTA] n 在形成过程中会产生H+,这些H+会吸附在配合物表面或结合形成气相氢分子[32]。除形成配合物[BTA-Al-BTA] n 外,BTA还可通过式(3)所示机制与Al发生反应,形成Al-BTA的强保护层,阻断水扩散的通道。
HuangG L, XueM L, ZiY Z. Review on the corrosion and protection mechanism of metal materials[J]. World Nonferrous Metals, 2018(6): 217-218.
[2]
ZhangD Q, GaoL X, ZhouG D. Research, development and prospect of corrosion inhibitors athome and abroad[J]. Corrosion and Protection, 2009, 30: 604-610.
[3]
ZouX, XiangQ, HaoJ, et al. Scalable modulation of reduced graphene oxide properties via regulatinggraphite oxide precursors[J]. Journal of Alloys and Compounds, 2019, 791: 423-430.
LiXiao-lin, KongGang, CheChun-shan,et al. Research progress of modified graphene oxide in metal anti-corrosion coatings[J]. Electroplating and Coating, 2021, 40(12): 929-936.
[6]
MohammadkhaniR, RamezanzadehM, SaadatmandiS, et al. Designing a dual-functional epoxy composite system with self-healing/barrier anti-corrosion performance using graphene oxide nano-scale platforms decorated with zinc doped-conductive polypyrrole nanoparticles with great environmental stability and non-toxicity[J].Chemical Engineering Journal, 2020,382: 122819.
[7]
HaoY S, ZhaoY F, LiB, et al. Self-healing effect of graphene@PANI loaded with benzotriazole for carbon steel [J]. Corrosion Science, 2020, 163: 108246.
[8]
KasaeianM, GhasemiE, RamezanzadehB, et al. Construction of a highly effective self-repair corrosion-resistant epoxy composite through impregnation of 1H-Benzimidazole corrosion inhibitor modified graphene oxide nanosheets (GO-BIM)[J]. Corrosion Science, 2018, 145: 119-134.
[9]
GarciaH M, JimenezM A, CasalB, et al. Preparation and electrochemical study of cerium-silica sol-gel thin films[J]. Journal of Alloys and Compounds, 2004, 380(1/2): 219-224.
ZhouY, ZuoY, LinB. The compounded inhibition of sodium molybdate and benzotriazole on pitting corrosion of Q235 steel in NaCl+NaHCO3 solution[J]. Materials Chemistry and Physics, 2017, 192: 86-93.
[12]
HuangY, LiuT, MaL, et al. Saline-responsive triple-action self-healing coating for intelligent corrosion control[J]. Materials & Design, 2022, 214: 110381.
ZhaoYi-fan. Preparation and anti-corrosion mechanism of polyaniline nano self-healing coatings[D]. Shenyang: School of Materials Science and Engineering, Shenyang University of Chemical Technology, 2019
BiJin-ye. Preparation and anti-corrosion performance of polyaniline/epoxy coatings loaded with benzotriazole[D]. Guangzhou: School of Machanical & Automotive Engineering, South China University of Technology, 2022
[17]
CaiK, ZuoS, LuoS, et al. Preparation of polyaniline/graphene composites with excellent anti-corrosionproperties and their application in waterborne polyurethane anticorrosive coatings[J]. RSC Advances, 2016(98): 95965-95972.
LiHong-ling. The effect of KH-151 silane modified nano ZrO2 on the protective performance of epoxy resin coatings on aluminum alloy surfaces [J]. Corrosion and Protection, 2023, 44(9): 83-89.
[23]
LiuX, ZhangD, HouP, et al. Preparation and characterization of polyelectrolyte-modified attapulgite as nanocontainers for protection of carbon steel[J]. Journal of the Electrochemical Society, 2018, 165(13): 907-915.
[24]
GaoZ, FengW, ChangJ, et al. Chemically grafted graphene-polyaniline composite for application in supercapacitor[J]. Electrochimica Acta, 2014, 133(7): 325-334.
[25]
ChatterjeeS, LayekR K, NandiA K. Changing the morphology of polyaniline from a nanotube to a flat rectangular nanopipe by polymerizing in the presence of amino-functionalized reduced graphene oxide and its resulting increase in photocurrent[J]. Carbon, 2013, 52: 509-519.
[26]
KotalM, BhowmickA K. Multifunctional hybrid materials based on carbon nanotube chemically bonded to reduced graphene oxide[J]. Journal of Physical Chemistry C, 2013, 117(48): 25865-25875.
[27]
CruzS R, RomeroG J, AnguloS J L, et al. Comparative study of polyaniline cast films prepared from enzymatically and chemically synthesized polyaniline[J]. Polymer, 2004, 45(14): 4711-4717.
[28]
PolingG W. Reflection infra-red studies of films formed by benzotriazole on Cu[J]. Corrosion Science,1970, 10(5): 359-370.
[29]
ChenY, JiangY Y, YeZ Y, et al. Adsorption dynamics of benzotriazole on copper in chloride solution[J]. Corrosion, 2013, 69(9): 886-892.
[30]
ZhangB, HeC, ChengW, et al. Synergistic corrosion inhibition of environment-friendly inhibitors on the corrosion of carbon steel in soft water[J]. Corrosion Science, 2015, 94(5): 6-20.
[31]
OkaforP C, ZhengY. Synergistic inhibition behaviour of methylbenzyl quaternary imidazoline derivative and iodide ions on mild steel in HSO solutions[J]. Corrosion Science, 2009, 51(4): 850-859.
[32]
RamezanzadehB, NiroumandradS, AhmadiA, et al. Enhancement of barrier and corrosion protection performance of an epoxy coating through wet transfer of amino functionalized graphene oxide[J]. Corrosion Science, 2016, 103: 283-304.
[33]
GuptaG, BirbilisN, CookA B, et al. Polyaniline-lignosulfonate/epoxy coating for corrosion protection of AA2024-T3[J]. Corrosion Science, 2013, 67: 256-267.
[34]
FahlmanM, JastyS, EpsteinA J. Corrosion protection of iron/steel by emeraldine base polyaniline: an X-ray photoelectron spectroscopy study[J]. Synthetic Metals, 1997, 85(1): 1323-1326.
[35]
ChenZ, HuangL, ZhangG, et al. Benzotriazole as a volatile corrosion inhibitor during the early stage of copper corrosion under adsorbed thin electrolyte layers[J]. Corrosion Science, 2012, 65: 214-222.
[36]
GattinoniC, MichaelidesA. Understanding corrosion inhibition with van der Waals DFT methods: the case of benzotriazole[J]. Faraday Discussions, 2015, 180: 439-458.