Insight into the anti–corrosion performance of Artemisia argyi leaves extract as eco–friendly corrosion inhibitor for carbon steel in HCl medium

At present, an important goal in the field of corrosion is to develop effective and environment–friendly corrosion inhibitors. Newly developed corrosion inhibitors can be used to substitute conventional corrosion inhibitors, which are toxic and undegradable. Herein, Artemisia argyi leaves extract (ALE) as high–efficiency corrosion inhibitor of carbon steel in HCl solution was investigated. The functional groups of ALE were characterized by Fourier transform infrared spectroscopy (FTIR). Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curve (Tafel), scanning electron microscopy (SEM), quantum chemical (QC) calculations, and molecular dynamics simulation (MDS) were used to examine the inhibitory performance and mechanism of ALE. The findings indicate that ALE is a good mixed–type corrosion inhibitor. It can be used to slow down the corrosion of carbon steel in HCl, with a maximum inhibition efficiency of 96.4% at 298 K. In addition, the Langmuir adsorption model is used to explain the adsorption of this corrosion inhibitor on carbon steel surfaces. Furthermore, the corrosion inhibition mechanism of ALE can be proved by quantum calculation results and molecular dynamics simulations.     

Wear in total knee arthroplasty—just a question of polyethylene?: Metal ion release in total knee arthroplasty

Purpose

Biological reactions against wear particles are a common cause for revision in total knee arthroplasty. To date, wear has mainly been attributed to polyethylene. However, the implants have large metallic surfaces that also could potentially lead to metal wear products (metal ions and debris). The aim of this study was to determine the local release of cobalt, chromium, molybdenum and titanium in total knee arthroplasty during a standard knee wear test.

Methods

Four moderately conforming fixed-bearing implants were subjected to physiological loadings and motions for 5×10⁶ walking cycles in a knee wear simulator. Polyethylene wear was determined gravimetrically and the release of metallic wear products was measured using high resolution-inductively coupled plasma-mass spectrometry.

Results

A polyethylene wear rate of 7.28 ± 0.27 mg/10⁶ cycles was determined and the cumulative mass of released metals measured 1.63 ± 0.28 mg for cobalt, 0.47 ± 0.06 mg for chromium, 0.42 ± 0.06 mg for molybdenum and 1.28 ± 0.14 mg for titanium.

Conclusion

For other metallic implants such as metal-on-metal total hip arthroplasty, the metal wear products can interact with the immune system, potentially leading to immunotoxic effects. In this study about 12 % by weight of the wear products were metallic, and these particles and ions may become clinically relevant for patients sensitive to these materials in particular. Non-metallic materials (e.g. ceramics or suitable coatings) may be considered for an alternative treatment for those patients.     

In vitro biocompatibility of CoCrMo dental alloys fabricated by selective laser melting

Objective

Selective laser melting (SLM) is increasingly used for the fabrication of customized dental components made of metal alloys such as CoCrMo. The main aim of the present study is to elucidate the influence of the non-equilibrium microstructure obtained by SLM on corrosion susceptibility and extent of metal release (measure of biocompatibility).

Methods

A multi-analytical approach has been employed by combining microscopic and bulk compositional tools with electrochemical techniques and chemical analyses of metals in biologically relevant fluids for three differently SLM fabricated CoCrMo alloys and one cast CoCrMo alloy used for comparison.

Results

Rapid cooling and strong temperature gradients during laser melting resulted in the formation of a fine cellular structure with cell boundaries enriched in Mo (Co depleted), and suppression of carbide precipitation and formation of a martensitic ? (hcp) phase at the surface. These features were shown to decrease the corrosion and metal release susceptibility of the SLM alloys compared with the cast alloy. Unique textures formed in the pattern of the melting pools of the three different laser melted CoCrMo alloys predominantly explain observed small, though significant, differences. The susceptibility for corrosion and metal release increased with an increased number (area) of laser melt pool boundaries.

Significance

This study shows that integrative and interdisciplinary studies of microstructural characteristics, corrosion, and metal release are essential to assess and consider during the design and fabrication of CoCrMo dental components of optimal biocompatibility. The reason is that the extent of metal release from CoCrMo is dependent on fabrication procedures.     

芳烷基酚树脂在98%硫酸中腐蚀行为研究

用失重和表面腐蚀层厚度的测定以及借助于Ｘ光电子能谱（ＸＰＳ）、红外吸收光谱（ＦＴ—ＩＲ）、扫描电子显微镜（ＳＥＭ）等分析手段研究芳烷基酚树脂在浓硫酸中的腐蚀行为。探讨耐浓硫酸腐蚀机理模型。结果表明试样经一定时间浸泡后表面腐蚀层厚度对温度和作用时间没有依赖关系，该材料耐浓硫酸腐蚀。腐蚀机理为：浸泡过程中，试样表面形成了一层结构致密的耐腐蚀物质，阻止了硫酸分子进一步向试样内部扩散渗透，使试样内部免遭进一步破坏。     

Electrochemical impedance spectroscopy study of the adsorption behaviour of α-lactalbumin and β-casein at stainless steel

The electrocatalytic reduction of tert-butyl hydroperoxide and cumyl hydroperoxide at platinum and glassy carbon disc microelectrodes has been investigated in N,N-dimethylformamide and 1,2-dichloroethane in the presence of a small amount of iron (III) chloride in the solution. In the course of a negative scan, metallic iron was electrodeposited on the electrode, making possible the reduction of the hydroperoxide at the electrode surface. During the repetitions of the recordings, an unusual reproducibility of the reduction signal was observed. This reproducibility is due to an in situ reconstitution of the active surface of the electrode that allows the electrode reaction to take place, at each scan, on a clean non-contaminated new electrode surface.     

In vitro serum levels of metal ions released from orthopaedic implants

Metallic materials in orthopaedic implants must bear mechanical loads with resultant surface damage. In addition to mechanical load, the surface damage on the implants occurs due to electrochemical corrosion from the physiological environment in-vivo. This research investigates in vitro experimental test bodies (surface area: 4.71 cm²) of four different ISO (International Organization for Standardization) standardised, frequently used, artificial implant alloys (TiAl₆V₄, Ti, CoCr₂₉Mo, FeCrNiMoMnNbN). The test materials were immersed in inert polystyrene test tubes filled with 1 ml of serum (pH 7.4) by avoidance of any friction and mechanical load. Here, they were subject to electrochemical corrosion independently of mechanical influences when in contact with body liquids. It was found that up to 80% of the entire dissolution of each ion occurred within the first 24 h of immersion. Additionally, the dissolution of the metal ions depended on the proportional mix of the individual elements in respective alloys. Therefore, the highest percent of ion concentration was found for Co (CoCr₂₉Mo) followed by Fe (FeCrNiMoMnNbN) and Mo (FeCrNiMoMnNbN). The lowest percent of ion concentrations were evident for Ti (Ti), Cr (CoCr₂₉Mo) and Cr (FeCrNiMoMnNbN).None of the authors have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this article. The experiments performed in this in-vitro study comply with the current laws of Germany.     

Potential pharmacological treatments of prosthetic joint loosening

We are beginning to understand the biological events that lead to aseptic loosening of total joint prostheses. Particles of wear, mostly liberated from the articulating surfaces of implants, are phagocytosed by macrophages and induce the release of inflammatory mediators (such as interleukin-1, tumour necrosis factor, interleukin-6 and prostaglandin E₂) or cause cell death. These biological responses are thought to cause the bone loss that leads to prosthetic loosening. Drugs that suppress inflammatory mediators are successfully used to treat inflammatory diseases. Certain drugs can also reduce the corrosion of metal wear particles inside macrophages which enhances mediator release or cell death. Here we consider the prospect that these pharmacological treatments may enhance the long-term survival of implants.     

表面涂层技术对镍铬合金耐蚀性能的影响

目的在模拟口腔环境中,研究镍铬合金表面涂钛前后,对抗酸腐蚀能力的变化。方法采用溶胶-凝胶沉积金属钛的表面涂层法,应用ZF-3恒电位仪,测定镍铬合金表面涂钛前后,在不同pH值条件下的极化曲线。结果镍铬合金表面涂钛处理前,pH=7.0时,电极电位为-160mV,自腐蚀电流密度为0.262μA·cm-2;pH=5.6时,分别为-182mV及0.352μA·cm-2。随着pH值降低,电位和电流密度下降,材料容易被腐蚀。涂钛处理后,pH=7.0时,电极电位为-71mV,自腐蚀电流密度为0.152μA·cm-2;pH=5.6时,分别为-89mV及0.174μA·cm-2,表明涂钛后,材料的腐蚀速度降低。结论不论涂钛前或涂钛后,酸性环境同样使镍铬合金耐腐蚀能力下降;而在酸性环境,涂钛后镍铬合金耐蚀性能优于涂钛前,中性环境也如此。说明镍铬合金表面涂钛能提高金属的耐酸性能。     

Surface enhanced Raman scattering (SERS) of 1-hydroxybenzotriazole adsorbed on a copper electrode surface

The adsorption of 1-hydroxybenzotriazole (BTAOH) on the copper electrode was studied by surface-enhanced Raman scattering spectroscopy (SERS) as a function of electrode potential and pH value of the solution. A striking similarity between the SERS spectra of BTAOH and the respective spectra of benzotriazole (BTAH) was observed in spite of significant differences in the normal Raman spectra of these compounds. A hypothesis assuming transformation of the BTAOH molecule into BTAH at the copper surface has been verified by H/D isotopic exchange experiments. The unique sensitivity of the SERS spectrum to isotopic exchange found in acidic medium (pH 2) at considerably negative electrode potentials together with some differences between the SERS spectra of BTAOH and BTAH indicated that BTAOH is mainly adsorbed in its molecular form. However, the transformation from the adsorbed BTAOH molecule to the surface complex of BTA^? anion with Cu(I) was suggested for alkaline solutions and potentials more positive than ?0.2 V.     

茸毛链球菌对四种烤瓷合金腐蚀行为的影响

目的:研究口腔茸毛链球菌对4种烤瓷合金腐蚀性的影响,并探讨其影响是否因细菌作用环境不同而存在变化。方法:将受试合金与茸毛链球菌在固体或液体培养基中共同培养,以单纯培养基和空白组作为对照,10周后,用电化学方法对测试材料行动电位极化扫描,Corrview2腐蚀分析软件分析获得材料Icorr、Ecorr和Etp,并以场发射扫描电镜观察腐蚀后合金表面形貌。结果:电化学测试结果显示,细菌作用组(C组和D组)较无细菌作用组(B组)自腐蚀电位值偏负,且各合金液体培养基作用组(C组)较固体培养基组(D组)更负。SEM观察到合金表面孔蚀点。而无细菌作用的单纯培养基作用组(B组)较空白组(A组)自腐蚀电位值偏正。结论:口腔茸毛链球菌能够增加烤瓷合金的腐蚀倾向,使合金更易发生腐蚀;且口腔细菌在液体环境较固体环境对合金耐蚀性影响更大。