Electrosysnthesis of poly(aniline-co-m-amino benzoic acid) for corrosion protection of steel

Conducting polymer (poly(aniline-co-m-amino benzoic acid)) has been deposited on steel surface by cyclic voltammetric technique. The copolymer film was characterized by FTIR, XPS and SEM techniques. The corrosion protection performance of copolymer film on steel was found out by impedance and tafel polarization methods in 1N HCl. The copolymer film was found to be highly corrosion resistant.     

Effect of chromium on the corrosion behavior of iron aluminides in thiosulfate-chloride solution

Aqueous corrosion characteristics of iron aluminides in thiosulfate-chloride solution were studied as a function of chromium addition. Four kinds of iron aluminides, namely, FA-61, FA-77, FA-72 and FA-78, were prepared by arc melting followed by thermomechanical treatment. The corrosion behavior in thiosulfate-chloride solution for the prepared alloys were investigated by electrochemical tests (potentiodynamic test, potentiostatic test and electrochemical impedance spectroscopy (EIS) measurement) and surface analyses. The results of the potentiodynamic test indicated that the breakdown potential increased with increasing Cr content. Cr additions were found to prevent passive film from undergoing pitting corrosion. In EIS measurement, the depression angle was inversely related to pitting resistance, and decreased with increasing chromium content. The SEM observations of the sample surfaces reveal the different forms of pit as a function of chromium content. The AES results give evidence that the thiosulfate ions are reduced on the metallic surface, which inhibits the repassivation process.     

Development and characterization of sol‐gel composite coatings on aluminum alloys for corrosion protection

For several years, Cr^IV compounds were used as effective and inexpensive corrosion inhibitors. Studies showed that these materials were toxic and carcinogenic. This has led to extensive research to develop alternative inhibitors. Organo‐silicate hybrid coatings appeared as an effective technique for forming protective layers on different metal alloys. A silane film was obtained by dip coating of the sample in sol solution prepared from the hydrolysis of 3‐glycidoxypropyltrimethoxysilane (GPTM), tetraethylorthosilicate (TEOS) with acid as catalyst and water as solvent instead of VOC (volatile organic compound). The sol solution was aged at ambient temperature to to enhance the effectiveness of the solution for the hydrolysis process. The sample was cured at 150 °C to ensure cross‐linking of the film. The experiments have shown that heat treatment leads to increased density and corrosion resistance of the films. Organic and inorganic inhibitors were added in different concentrations to improve the protection and self‐healing properties of the coating even after long‐time immersion in corrosive solution. The protection performance of the film was evaluated by electrochemical impedance spectroscopy (EIS) in 0.5 M NaCl solution (pH value 7). The surface morphologies of the treated samples were investigated using SEM.     

Effects of 5-(3-aminophenyl)-tetrazole on the inhibition of unalloyed iron corrosion in aerated 3.5% sodium chloride solutions as a corrosion inhibitor

The effects of 5-(3-aminophenyl)-tetrazole (APT) on the inhibition of unalloyed iron corrosion in aerated 3.5% NaCl solutions as a corrosion inhibitor have been studied using open circuit potential (OCP), cyclic potentiodynamic polarization (CPP), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) measurements. The inhibited iron surface was characterized by scanning electron spectroscopy (SEM) and energy dispersive X-ray (EDS) investigations. The OCP showed positive shifts of potential in the presence of APT and the increase of its concentration. CPP and CA measurements indicated that APT molecules decrease the pitting and uniform corrosions through decreasing the pitting and absolute currents, and corrosion rate as well as shifting the corrosion and pitting potentials of iron towards the noble values. EIS plots revealed that APT increases the surface and polarization resistances of iron. SEM/EDS investigations proved that the inhibition of iron corrosion in NaCl containing APT solutions is achieved by the adsorption of APT molecules onto iron to preclude the dissolution process by blocking the active sites on its surface.     

化学氧化合成N-乙基苯胺与苯胺共聚物的防腐性能

通过开路电位法详细研究了掺杂酸种类、掺杂状态和共聚单体摩尔比等对化学氧化合成的N-乙基苯胺与苯胺(EA/AN)共聚物的防腐性能的影响。结果表明,所有EA/AN共聚物的防腐性能均优于两种单体的均聚物,单体喂入摩尔比EA/AN为20/80的去掺杂态共聚物表现出最优防腐效果。盐酸掺杂共聚物的防腐性能优于其它酸掺杂共聚物的,去掺杂态共聚物又优于掺杂态共聚物。尤其是在强酸性腐蚀介质中,以该共聚物为底漆,环氧树脂为面漆的复合涂层钢板的开路电位在浸泡过程中出现了不降反升现象,涨幅达110 mV左右,较裸露钢板相应正移了约545 mV,较聚苯胺复合涂层涂覆的钢板相应正移了约90 mV,在长达半年的浸泡后,涂层不脱落、不起泡,也无锈点出现。     

反应溅射TiN纳米晶薄膜的结构特征和耐蚀性

利用直流反应溅射技术在不锈钢和硅基体上沉积了TiN纳米晶薄膜,采用场发射扫描电镜(FESEM)、X射线衍射(XRD)和电化学阻抗谱(EIS)技术研究了薄膜的表面形貌、相结构和耐蚀性与偏压的关系。结果表明,TiN薄膜的表面结构明显取决于所施加的偏压,适当提高偏压有利于获得细小、均匀、致密和光滑的膜层。XRD分析发现,TiN薄膜为面心立方结构,其择优取向为(111)面。实验显示,对应0V和-35V偏压的薄膜为欠化学计量比的,而偏压增加至-70V和-105V时的薄膜为化学计量比的TiN。EIS结果表明,较高偏压下的TiN薄膜几乎在整个频率范围内均表现为容抗特征,其阻抗模值明显高于低偏压下的膜层,这主要与较高偏压下的薄膜具有相对致密的微结构有关。较低偏压的TiN薄膜因结构缺陷较多其耐蚀性低于基体不锈钢。EIS所揭示的薄膜结构特征与FESEM观测结果一致。可见,减少穿膜针孔等结构缺陷有利于改善反应溅射TiN纳米晶薄膜耐蚀性。     

耐海水腐蚀铸铁保护膜的形成

研究表明，对普通灰铸铁加少量合金元素及变质剂，可使使其耐海水腐蚀率提高４倍；这是由于在腐蚀过程中，铸铁表面形成了一层复合保护膜，对该膜的形成过程进行了探讨，发现了一些有意义的新现象。     

An electrochemical,in vitro bioactivity,and quantum chemical approach to nanostructured copolymer coatings for orthopedic applications

Conducting polymers represent a promising platform toward coating materials for implant technologies in recent years. In this investigation, copolymers based on pyrrole (Py) and 3,4-ethylenedioxythiophene (EDOT) were electrodeposited on 316L SS with various feed ratio of Py/EDOT through cyclic voltammetric technique. The surface and chemical structure of the synthesized copolymers were analyzed by SEM, AFM, FT-IR, and ¹H NMR spectroscopic analysis. The influence of comonomer feed ratio on electrochemical corrosion behavior was investigated in stimulated body fluid. A significant lower corrosion current with nobler shift in corrosion potential and higher charge transfer resistance values of copolymer-coated 316L SS were obtained and the comparisons were made with uncoated as well as their homo polymers. Furthermore, in vitro cell culture studies were performed on MG63 osteoblast human cells to confirm the biocompatibility of copolymer coatings. Quantum chemical approach was employed to verify the obtained experimental outcomes. As a result of this investigation, it was concluded that the performance of coatings was strongly dependent to the monomer feed ratio and the copolymer synthesized with 50:50 feed ratio showed high corrosion protection efficiency with improved cell growth on MG63 osteoblast cell.     

氧化铈膜制备及其耐腐蚀性能

采用不同的制备溶液及制备参数在X80钢表面制备出不同的氧化铈膜,并对其耐腐蚀性能进行了研究.利用扫描电镜、能谱仪、XRD、拉曼光谱、接触角测试仪对不同的氧化铈膜腐蚀前后的表面形貌、元素、物相及亲水性进行了分析,利用电化学工作站对不同的氧化铈膜在3.5wt.％NaCl溶液中的开路电位、线性极化电阻、交流阻抗、极化曲线进行...     

含Zn-Al磷酸盐防腐蚀涂层的制备与腐蚀机理研究

为制备出具有更高耐蚀性、尤其是耐海洋气候腐蚀的Zn-Al基金属陶瓷涂层,以磷酸二氢铝作为粘结剂,氧化镁、氧化锌作为固化剂,锌、铝粉作为填料,聚四氟乙烯作为助剂,制备了一种含Zn-Al磷酸盐防腐蚀涂料,通过空气喷涂后热固化的方式在300M高强钢表面制备出含Zn-Al磷酸盐防腐蚀涂层,并对涂层进行了中性盐雾试验以及电化学试验,采用扫描电镜和能谱分析形貌及成分。结果表明:涂层中性盐雾腐蚀寿命达到1 000 h;涂层的自腐蚀电位低于基体,能为基体提供阴极保护;含Zn-Al磷酸盐防腐蚀涂层的腐蚀过程分为4个阶段,涂层的主要防护机制为金属粉的牺牲阳极作用和腐蚀产物的屏蔽效应。     

铜离子及电位对5083铝合金阴极保护行为的影响

目前有关船体防污涂料中的铜离子及阴极保护电位对铝合金船体的腐蚀电化学研究不够深入。通过极化试验、电化学阻抗谱(EIS)测试及外加恒电位阴极保护试验,并结合腐蚀形貌观察,研究了5083铝合金在有无Cu~(2+)的3.5%NaCl溶液中的极化及腐蚀特性,并结合不同电位下的阴极保护行为,探讨了其阴极保护电位范围。结果表明:防污剂中的Cu~(2+)沉积在铝合金基体表面会造成防腐蚀性能下降,降低铝合金舰船的阴极保护效果,应该避免Cu~(2+)的渗入;阴极保护电位过正,保护效果不佳,会造成铝合金表面发生点蚀,但若阴极保护电位过负,表面会发生析氢腐蚀,因此其合理的阴极保护电位范围为-1.00~-1.10 V(vs SCE)。     

Nanostructuration of self-assembled poly(styrene-b-isoprene-b-styrene) block copolymer thin films in a highly oriented pyrolytic graphite substrate

Highly oriented pyrolitic graphite (HOPG) is a useful substrate to visualize epitaxial formation due to its crystallographic structure. The morphology of a poly(styrene-b-isoprene-b-styrene) block copolymer thin film on a HOPG substrate was investigated by atomic force microscopy. Block copolymer domains generated a morphology with triangular regularity. This arrangement was induced by the HOPG substrate structure due to van der Waals attraction between the HOPG π-conjugated system and aromatic ring of polystyrene domains. However, increasing the film thickness, the substrate effect on the surface morphology decreased. As a consequence, film surfaces showed the coexistence of different structures such as highly aligned cylinders and perforated lamellae. When film thickness exceeded a threshold value, the substrate did not have effect in the surface arrangements and the surface showed a similar morphology to that existing in bulk.     

AM355不锈钢在酸性溶液中的腐蚀电化学行为

结合腐蚀形貌,通过极化曲线、交流阻抗谱(EIS)和莫特肖特基(MS)曲线的测定,分析了溶液pH值对AM355不锈钢腐蚀电化学行为的影响。结果表明:随溶液pH值的减小,腐蚀电位正移,腐蚀电流密度增大,致钝电位发生了正移,致钝电流密度、维钝电流密度增大。钝化膜由铬氧化物和铁氧化物组成,酸性增加使得铁氧化物施主浓度增大,钝化膜表面吸附氢离子电荷密度增加。钝化膜的厚度及其电阻随pH值的减小而减小,钝化膜更容易被破坏,酸性达到一定程度,钝化膜局部区域优先腐蚀。溶液pH值减小,AM355在溶液中保持自钝化性能降低,材料的腐蚀速率增加。     

植酸在镁合金表面处理中的应用研究

采用稀土铈盐在镁合金表面生成了化学转化膜,通过扫描电镜、能谱分析等手段研究了采用植酸对镁合金表面及其表面化学转化膜进行后处理的改性作用,讨论了植酸浸泡溶液与工艺参数对吸附膜增重的影响.研究表明,镁合金表面植酸浸泡吸附膜以及化学转化膜植酸浸泡处理后膜层的增重随植酸浓度的增加、温度的升高及时间的延长而增大,所得化学转化膜经植酸浸泡处理可改善膜层表面龟裂,提高镁合金及其表面转化膜的耐蚀性,代替对环境污染严重的铬酸盐处理技术;并对镁合金表面膜的微观形貌与元素组成进行了表征.     

三氟丙烯-醋酸乙烯酯共聚物及水解产物的表面性质

研究3,3,3-三氟丙烯结合量不同的三氟丙烯-醋酸乙烯酯共聚物的酸催化水解反应,并用红外光谱、凝胶色谱、氟离子选择电极电位分析法和差热分析等方法表征聚合物的结构、组成和性能随水解度不同引起的变化。结果表明:共聚物的酯基的水解度随水解时间的延长而增大,72h酯基的转化率可达99%,随着水解度的增大,共聚物的玻璃化转变温度Tg逐渐升高,表面能逐渐增大,明显地呈现表面活性剂性质,但共聚物的数均分子量(Mn)、重均分子量(Mw)及其分布指数(IPDI)变化不大。     

Anti-fouling properties of polylactic acid film modified by pegylated phosphorylcholine derivatives

Anti-fouling properties are important for both pharmaceutical and biomedical applications of polylactic acid (PLA). In this study, highly hydrated hydrophilic bilayers containing phosphatidylcholine (PC) and polyethylene glycol (PEG) were applied to PLA films to prevent the protein adsorption and blood platelet adhesion. The PLA films were coated with three PLA copolymers of PC and PEG, namely, a PLA-b-PEG block copolymer with a PC group on the end of a PEG chain (PC-PEG-PLA), a poly[2-methacryloyloxyethyl phosphatidylcholine (MPC)]-PLA graft copolymer (PMPC-g-PLA), and a PMPC-PLA graft copolymer with PEG serving as a spacer (PMPC-g-(PEG-b-PLA)). The influence of the copolymer structure on the anti-fouling properties of PLA film was then investigated. The results showed that the introduction of PC and PEG polar copolymers decreased the water-contact angle (WCA) and increased the equilibrated degree of hydration (H_eq) of the PLA surface significantly. The PMPC-g-(PEG-b-PLA) copolymer achieved the lowest WCA value and the highest H_eq value as it provided a higher density of PC on the outer surface. In addition, the strong hydration of the PEG and PC groups efficiently suppressed the bovine serum albumin (BSA) and fibrinogen (Fg) adsorption and subsequently inhibited platelet adhesion. The above results demonstrated that a good “anti-fouling” surface layer on the PLA substrate could be achieved by a combination of PEG and PC in copolymers.     

Chemical treatment of zinc surface and its corrosion inhibition studies

The surface treatment of zinc and its corrosion inhibition was studied using a product (BTSC) formed in the reaction between benzaldehyde and thiosemicarbozide. The corrosion behaviour of chemically treated zinc surface was investigated in aqueous chloride-sulphate medium using galvanostatic polarization technique. Zinc samples treated in BTSC solution exhibited good corrosion resistance. The measured electrochemical data indicated a basic modification of the cathode reaction during corrosion of treated zinc. The corrosion protection may be explained on the basis of adsorption and formation of BTSC film on zinc surface. The film was binding strongly to the metal surface through nitrogen and sulphur atoms of the product. The formation of film on the zinc surface was established by surface analysis techniques such as scanning electron microscopy (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR).     

电解液组成对AZ91D镁合金微弧氧化的影响

在含有NaAlO2、KF的电解质溶液中,采用恒电流方式对AZ91D镁合金进行微弧氧化获得陶瓷膜.研究了电解液组分及浓度对陶瓷氧化膜厚度及表面形貌的影响,同时,采用动电位极化曲线及电化学交流阻抗评价了陶瓷氧化膜的耐蚀性.研究发现:NaAlO2单独存在时即可产生火花放电现象,但得到的氧化膜较薄;氟化钾的加入可以显著增加氧化膜厚度,膜厚的增长速度与氟化钾的加入量呈线性关系.SEM表面形貌分析表明:电解质浓度较低时产生的氧化膜宏观上较粗糙、微观上颗粒结合紧密;高浓度时得到的氧化膜宏观上细致光滑,微观上存在明显的孔洞和放电隧道,呈熔融状态结合在一起.动电位极化曲线及电化学交流阻抗的测试一致表明,经微弧氧化处理后的镁合金耐蚀性显著提高.     

In vitro corrosion behaviour of Ti–Nb–Sn shape memory alloys in Ringer’s physiological solution

The nearly equiatomic Ni–Ti alloy (Nitinol) has been widely employed in the medical and dental fields owing to its shape memory or superelastic properties. The main concern about the use of this alloy derives form the fact that it contains a large amount of nickel (55% by mass), which is suspected responsible for allergic, toxic and carcinogenic reactions. In this work, the in vitro corrosion behavior of two Ti–Nb–Sn shape memory alloys, Ti–16Nb–5Sn and Ti–18Nb–4Sn (mass%) has been investigated and compared with that of Nitinol. The in vitro corrosion resistance was assessed in naturally aerated Ringer’s physiological solution at 37°C by corrosion potential and electrochemical impedance spectroscopy (EIS) measurements as a function of exposure time, and potentiodynamic polarization curves. Corrosion potential values indicated that both Ni–Ti and Ti–Nb–Sn alloys undergo spontaneous passivation due to spontaneously formed oxide film passivating the metallic surface, in the aggressive environment. It also indicated that the tendency for the formation of a spontaneous oxide is greater for the Ti–18Nb–5Sn alloy. Significantly low anodic current density values were obtained from the polarization curves, indicating a typical passive behaviour for all investigated alloys, but Nitinol exhibited breakdown of passivity at potentials above approximately 450 mV(SCE), suggesting lower corrosion protection characteristics of its oxide film compared to the Ti–Nb–Sn alloys. EIS studies showed high impedance values for all samples, increasing with exposure time, indicating an improvement in corrosion resistance of the spontaneous oxide film. The obtained EIS spectra were analyzed using an equivalent electrical circuit representing a duplex structure oxide film, composed by an outer and porous layer (low resistance), and an inner barrier layer (high resistance) mainly responsible for the alloys corrosion resistance. The resistance of passive film present on the metals’ surface increases with exposure time displaying the highest values to Ti–18Nb–4Sn alloy. All these electrochemical results suggest that Ti–Nb–Sn alloys are promising materials for biomedical applications.     

Study of the in vitro corrosion behavior and biocompatibility of Zr-2.5Nb and Zr-1.5Nb-1Ta (at%) crystalline alloys

The in vitro corrosion behavior and biocompatibility of two Zr alloys, Zr-2.5Nb, employed for the manufacture of CANDU reactor pressure tubes, and Zr-1.5Nb-1Ta (at%), for use as implant materials have been assessed and compared with those of Grade 2 Ti, which is known to be a highly compatible metallic biomaterial. The in vitro corrosion resistance was investigated by open circuit potential and electrochemical impedance spectroscopy (EIS) measurements, as a function of exposure time to an artificial physiological environment (Ringer’s solution). Open circuit potential values indicated that both the Zr alloys and Grade 2 Ti undergo spontaneous passivation due to spontaneously formed oxide film passivating the metallic surface, in the aggressive environment. It also indicated that the tendency for the formation of a spontaneous oxide is greater for the Zr-1.5Nb-1Ta alloy and that this oxide has better corrosion protection characteristics than the ones formed on Grade 2 Ti or on the Zr-2.5Nb alloy. EIS study showed high impedance values for all samples, increasing with exposure time, indicating an improvement in corrosion resistance of the spontaneous oxide film. The fit obtained suggests a single passive film presents on the metals surface, improving their resistance with exposure time, presenting the highest values to the Zr-1.5Nb-1Ta alloy. For the biocompatibility analysis human osteosarcoma cell line (Saos-2) and human primary bone marrow stromal cells (BMSC) were used. Biocompatibility tests showed that Saos-2 cells grow rapidly, independently of the surface, due to reduced dependency from matrix deposition and microenvironment recognition. BMSC instead display a reduced proliferation, possibly caused by a reduced crosstalk with the metal surface microenvironment. However, once the substrate has been colonized, BMSC seem to respond properly to osteoinduction stimuli, thus supporting a substantial equivalence in the biocompatibility among the Zr alloys and Grade 2 titanium. In summary, high in vitro corrosion resistance together with satisfactory biocompatibility make the Zr-2.5Nb and Zr-1.5Nb-1Ta crystalline alloys promising biomaterials for surgical implants.