Abstract

The silane functionalized MnO₂ nanoparticles were incorporated in polythiophene (PT) to produce PT/silanes/MnO₂ nanocomposites. The surfaces of MnO₂ nanoparticles were modified with ethyltrimethoxysilane (ETMS), 3-glycidyloxypropyltrimethoxysilane (GPTMS), and 3-aminopropyltrimethoxysilane (APTMS) and characterized by X-ray diffraction (XRD) studies. The corrosion resistance of newly synthesized PT, PT-ETMS/MnO₂, PT-GPTMS/MnO₂, and PT-APTMS/MnO₂ composite coatings of magnesium alloy (AZ91A) was evaluated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) studies, and scanning electrochemical microscopy (SECM) immersed in natural seawater for several days. The PT-APTMS/MnO₂ nanocomposite coatings showed an excellent resistance against corrosion with a charge transfer resistance of over 7517.85 kΩ cm², which were higher than that of the PT coating (548.25 kΩ cm²) after 80 days immersion in seawater. The coating with MnO₂ nanoparticles modified by APTMS, GPTMS, and ETMS groups showed no significant penetration by corrosive ions during 80 days’ immersion due to the strong chemical bonding between amino/epoxide/ethyl groups on MnO₂ and the sulfur of PT. Decreased current was detected at the scratch of investigated nanocomposite coatings by SECM analysis. The affinity between PT and silanes/MnO₂ nanoparticles is enhanced due to their interfacial interactions, which improves the dispersion of silane functionalized MnO₂ nanoparticles in PT to produce uniform coatings. Scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) and XRD technique of synthesized nanocomposite coatings confirmed the presence of corrosion products which block the dissolution of Mg alloy. Excellent mechanical properties are shown by the investigated coatings.

• Highlights

• Newly synthesized polythiophene (PT), PT-ETMS/MnO₂, PT-GPTMS/MnO₂, and PT-APTMS/MnO₂ composite coatings on magnesium alloy (AZ91A) was evaluated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) studies, and scanning electrochemical microscopy (SECM) immersed in natural seawater for several days.

• The addition of MnO₂ in the polymer resulted in the reduction of porosity of the coatings significantly.

• The silane functionalized MnO₂ nanoparticles loaded nanocomposite coatings demonstrated excellent resistance against corrosion than that of the MnO₂-free PT coating after 80 days of immersion.

• The corrosion resistance of the coatings was considerably improved due to enhanced interfacial interactions between silane functionalized MnO₂ nanoparticles and PT by chemical bonding.

• The coating with MnO₂ nanoparticles modified by amino (APTMS), epoxide (GPTMS), and ethyl (ETMS) groups showed no significant penetration by corrosive ions during 80 days’ immersion due to the strong chemical bonding between amino/epoxide/ethyl groups on MnO₂ and a sulfur heterocycles of PT without changing the original crosslinking structure of PT.

• Interfacial interaction between phases also plays a key role in the affinity between MnO₂ and PT, which determines the dispersion of MnO₂ in coatings and uniform morphology of composite coatings.

摘要

将硅烷官能化的MnO ₂纳米颗粒掺入聚噻吩（PT）中，以生产PT /硅烷/ MnO ₂纳米复合材料。MnO ₂纳米颗粒的表面用乙基三甲氧基硅烷（ETMS），3-环氧丙氧基丙基三甲氧基硅烷（GPTMS）和3-氨基丙基三甲氧基硅烷（APTMS）改性，并通过X射线衍射（XRD）研究进行了表征。新合成的PT，PT-ETMS / MnO ₂，PT-GPTMS / MnO ₂和PT-APTMS / MnO ₂的耐腐蚀性通过电化学阻抗谱（EIS），电势极化（PDP）研究和浸没在天然海水中几天的扫描电化学显微镜（SECM）对镁合金（AZ91A）的复合涂层进行了评估。PT-APTMS / MnO ₂纳米复合涂层具有优异的耐腐蚀性能，其电荷转移电阻超过7517.85kΩcm ²，比在海水中浸泡80天后的PT涂层（548.25kΩcm ²）高。该涂层具有的MnO ₂由APTMS，GPTMS改性的纳米粒子，和ETMS组显示由腐蚀性离子期间80天浸入无显著渗透由于上的MnO氨基/环氧/乙酸乙酯基团之间的强的化学结合₂和PT的硫。通过SECM分析，在研究的纳米复合涂层的划痕处检测到电流减小。PT和硅烷/ MnO ₂纳米颗粒之间的界面相互作用增强了它们之间的亲和力，从而改善了硅烷官能化的MnO ₂纳米颗粒在PT中的分散性，从而产生了均匀的涂层。合成纳米复合涂层的扫描电子显微镜/能量色散X射线分析（SEM / EDX）和XRD技术证实了腐蚀产物的存在，这些腐蚀产物阻碍了Mg合金的溶解。所研究的涂层显示出优异的机械性能。

• 强调

• 通过电化学阻抗谱（EIS），电势极化（PDP）对镁合金（AZ91A）上的新合成聚噻吩（PT），PT-ETMS / MnO ₂，PT-GPTMS / MnO ₂和PT-APTMS / MnO ₂复合涂层进行了评估）研究，并将扫描电化学显微镜（SECM）浸入天然海水中数天。

• 聚合物中添加MnO ₂导致涂层孔隙率明显降低。

• 浸渍80天后，硅烷官能化的MnO ₂纳米颗粒负载的纳米复合涂层比无MnO _2的PT涂层具有优异的耐腐蚀性。

• 由于硅烷官能化的MnO ₂纳米颗粒与PT之间通过化学键合增强了界面相互作用，因此涂层的耐蚀性得到了显着改善。

• 氨基（APTMS），环氧化物（GPTMS）和乙基（ETMS）改性的MnO ₂纳米颗粒涂层由于在溶液中氨基/环氧化物/乙基之间的强化学键合，在浸泡80天后没有显示出腐蚀性离子的显着渗透。 MnO ₂和PT的硫杂环不改变PT的原始交联结构。

• 相之间的界面相互作用在MnO ₂和PT之间的亲和力中也起着关键作用，这决定了MnO ₂在涂层中的分散性和复合涂层的均匀形态。