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To improve corrosion resistance and enhance biocompatibility of magnesium alloy, cathodic plasma electrolysis (CPE), a liquid phase plasma technique, was used to fabricate zirconia (ZrO2) coatings onto WE43 magnesium alloy substrate. Surface morphology and phase composition of the coatings on magnesium alloy substrates were investigated by scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. The potentiodynamic polarization test in simulated body fluid (SBF) indicated that corrosion resistance of magnesium alloy was significantly improved by this CPE treatment. The results of cytocompatibility including osteoblasts adhesion and viability suggested that surface modification of magnesium alloy with ZrO2 coating fo'rmed via CPE technique is beneficial for cell proliferation and differentiation. The approach presented here should be an attractive way for surface modification of magnesium-based implants to improve anticorrosion and bone osseointegration. [ABSTRACT FROM AUTHOR]

A shape memory alloy with medical applications was analyzed by corrosion point of view in Fusayama artificial solution after few thousand experimental cycles. Scanning electrons microscope, EDAX and potentiostat equipments were used to characterize the material surface and its behavior during and after an electric polarization. Pitting corrosion type was observed on the surface with accentuated aspects based on the fatigue process. Dimensional characterization of the pitting holes was realized using 2D and 3D imaging software possibilities and chemical modifications were analyzed in and near the corrosion marks. [ABSTRACT FROM AUTHOR]

This paper is aimed at investigating the corrosion behavior of Pure and Zinc-graphite particles with percentage of 1, 3, and 5%, respectively. The composites were fabricated by powder metallurgy method. Corrosion tests were performed according to ASTM standard. Corrosion rate was calculated and it is found that in all cases the corrosion rate was decreasing with the increase in exposure time. Meanwhile, the microstructure of composites was imaged and analyzed using optical microscope and scanning electronmicroscope. It is observed that the best corrosion resistance was zinc with 1%Graphite while Zinc with 3%and 5%Graphite composites did not enhance the corrosion resistance comparing to pure Zinc. [ABSTRACT FROM AUTHOR]

Highlights: [•] Delayed and immediate crevice corrosions are investigated. [•] The crevice corrosion morphologies are studied by SEM. [•] The relocation of active dissolution region is observed. [•] The mechanisms of crevice corrosion are discussed in detail. [ABSTRACT FROM AUTHOR]

A thin film of Zn-Ni-FeO on steel substrates was prepared by electrodeposition technique using Zn-Ni alloy plating solution with nano-sized FeO particles. The cathodic polarization and cyclic voltammetry techniques were used to explain deposition process. The corrosion behavior of deposits was evaluated by polarization and impedance studies. Scanning electron microscope (SEM) images were used to study the surface morphology of coating. The grain size and amount of FeO particles present in composite coating were measured by X-ray diffraction pattern (XRD) and energy dispersive X-ray diffraction spectrometer (EDS), respectively. [ABSTRACT FROM AUTHOR]

Abstract: The influence of the quantity of the Mg2Sn phase on the corrosion behavior of different solution temperature treated Mg–7Sn magnesium alloy has been investigated by electrochemical measurements, scanning electron microscope (SEM) observation, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. With the increase of solution temperature, the quantity of Mg2Sn phase decreased and the tin concentration of matrix increased. The dissolved tin in Mg matrix took part in the film formation and the constituent of film was magnesium oxide and stannic oxide. The corrosion mode and corrosion rate were associated with the quantity of Mg2Sn phases and tin concentration of the matrix. If most of tin was present as Mg2Sn, the corrosion mode was pitting corrosion and it accelerated the corrosion rate. If most of tin was dissolved in matrix, the corrosion mode was filiform corrosion and it decreased the corrosion rate. The experiment evidences demonstrated that the corrosion resistance can be improved by increasing the tin concentration of matrix and the lowest corrosion rate was observed for sample solution treated at 540°C. [Copyright &y& Elsevier]

The 300 series stainless steels generally exhibit good corrosion resistance in common use. However, a premature fracture event caused by hydrogen embrittlement was encountered on 300 series stainless steels which was used as belt hanging chips in a tin plating process for the chip lead frame. The cause of the fracture was carefully studied. A metallurgical microscope and photoelectric direct reading spectrometer were used to examine the metallographic structures and chemical compositions of the matrix material. A scanning electron microscope and energy disperse spectroscope were also applied to analyze the micro morphologies and micro-area composition of the fracture. Meanwhile, the chemistry and hydrogen content of the process media were inspected by ion chromatography and hydrogen analyzer. In addition, the finite element method was employed to simulate the effect on the belt from the service conditions. The analysis results revealed that the unqualified material selection, the aggressive media, and the inappropriate technological parameters were the main causes of the failure. Furthermore, the mechanisms of hydrogen embrittlement were discussed, and countermeasures and suggestions were put forward. [ABSTRACT FROM AUTHOR]

Abstract: The effect of concentration on the corrosion behavior of Mg-based alloy AZ91D was investigated in ethylene glycol–water solutions using electrochemical techniques i.e. potentiodynamic polarization, electrochemical impedance measurements (EIS) and surface examination via scanning electron microscope (SEM) technique. This can provide a basis for developing new coolants for magnesium alloy engine blocks. Corrosion behavior of AZ91D alloy by coolant is important in the automotive industry. It was found that the corrosion rate of AZ91D alloy decreased with increasing concentration of ethylene glycol. For AZ91D alloy in chloride >0.05M or fluoride <0.05M containing 30% ethylene glycol solution, they are more corrosive than the blank (30% ethylene glycol–70% water). However, at concentrations <0.05 for chloride or >0.05M for fluoride containing ethylene glycol solution, some inhibition effect has been observed. The corrosion of AZ91D alloy in the blank can be effectively inhibited by addition of 0.05mM paracetamol that reacts with AZ91D alloy and forms a protective film on the surface at this concentration as confirmed by surface examination. [Copyright &y& Elsevier]

Abstract: The inhibition effect of glycine (Gly) towards the corrosion of low alloy steel ASTM A213 grade T22 boiler steel was studied in aerated stagnant 0.50M HCl solutions in the temperature range 20–60°C using potentiodynamic polarization (Tafel polarization and linear polarization) and impedance techniques, complemented with scanning electron microscope (SEM) and energy dispersive X-ray (EDX). Electrochemical frequency modulation (EFM), a non-destructive corrosion measurement technique that can directly give values of corrosion current without prior knowledge of Tafel constants, is also presented here. Experimental corrosion rates determined by the Tafel extrapolation method are compared with corrosion rates obtained by electrochemical, namely EFM technique, and chemical (i.e., non-electrochemical) method for steel in HCl. The chemical method of confirmation of the corrosion rates involved determination of the dissolved cation, using ICP-AES (inductively coupled plasma atomic emission spectrometry) method of analysis. Corrosion rates (in mm y−1) obtained from the electrochemical (Tafel extrapolation and EFM) and the chemical method, ICP, are in a good agreement. Polarization studies have shown that Gly is a good “green”, mixed-type inhibitor with cathodic predominance. The inhibition process was attributed to the formation of an adsorbed film on the metal surface that protects the metal against corrosive agents. Scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) examinations of the electrode surface confirmed the existence of such an adsorbed film. The inhibition efficiency increases with increase in Gly concentration, while it decreases with solution temperature. Temkin isotherm is successfully applied to describe the adsorption process. Thermodynamic functions for the adsorption process were determined. [Copyright &y& Elsevier]

Abstract: Electroless nickel plating on Mg–8Li alloy was studied, and an appropriate molybdate pretreatment was proposed. The pretreatment layer acted as an effective barrier and catalytic layer for the subsequent Ni–P plating. The coating was characterized by its structure, morphology, micro-hardness and corrosion resistance. Scanning Electronic Microscope (SEM) observation showed that the Ni–P coating was compact, uniform. The presence of molybdate pretreatment layer could reduce the potential difference between the Ni–P coating and the substrate, and enhanced the corrosion resistance of the alloy to certain extent. The electrochemical measurements showed that the sample with Ni–P film exhibited lower corrosion current density and more positive corrosion potential than the substrate. The hydrogen evolution tests further proved that the Ni–P coating provided good protection to the substrate. [Copyright &y& Elsevier]

Abstract  The influence of KCl(s) on the oxidation of Sanicro 28 (35Fe27Cr31Ni) austenitic stainless steel at 600 °C in 5% O2 + 40% H2O and in 5% O2 was investigated. The samples were coated with 0.1 mg/cm2 KCl(s) prior to exposure. The exposure time was 1, 24, 72 and 168 h. Uncoated samples were exposed for reference. The oxidized samples were analyzed by SEM/energy-dispersive X-ray (EDX), X-ray diffraction (XRD), and AES. The amount of chloride and chromate on the samples was analyzed quantitatively by ion chromatography after exposure. KCl(s) is very corrosive towards Sanicro 28. Corrosion is initiated by the formation of potassium chromate through the reaction of KCl(s) with the protective oxide, chloride leaving the sample in the form of HCl. Chromate formation is a sink for chromium in the oxide and leads to a deterioration of its protective properties. In the 5% O2 + 40% H2O environment, there is a stoichiometric relationship between the chromate formed and the chloride consumed. In dry O2 chromate formation is relatively slow, leaving more unreacted KCl(s) on the surface than in 5% O2 + 40% H2O. Once the protective, chromium-rich oxide has been depleted in chromium by chromate formation, the alloy becomes susceptible to direct attack by the remaining KCl(s). [ABSTRACT FROM AUTHOR]

Abstract: High-intensity pulsed ion beam (HIPIB) treatment is a new technology for surface modification of materials. In this paper, the surface of 316L stainless steel was irradiated by high-intensity pulsed ion beams at ion current density of 100, 200 and 300A/cm2 with 1, 5 and 10 shots. The surface morphology and the phase structure in the near surface region of original and treated samples were analyzed with scanning electron microscope (SEM) and X-ray diffraction (XRD). Electron probe microanalysis (EPMA) was used to study the distribution of elements on the irradiated surfaces. It is found that the HIPIB irradiation can smooth the surface of the targets, and a preferred orientation presents in the surface layer of the treated samples. Otherwise, selective ablation of impurities occurs during the interaction between HIPIB and the targets. The influence of HIPIB irradiation on the electrochemical corrosion resistance of 316L stainless steel in 0.5mol/L H2SO4 was investigated. The polarization curves show that under the cooperation of the smooth surface and the grain refinement with the selective ablation of impurities, the corrosion resistance of the irradiated samples was improved significantly. [Copyright &y& Elsevier]

Abstract: The electrochemical polishing of porous austenitic stainless steel (PASS), AISI 316L, in the phosphoric-sulfuric mixed acid with volume-ratio of 1:1, 2:1 and 3:1 at temperature ranging from 60 to 80 °C was studied. Electrochemical polishing of PASS was performed in the potential located in the limiting-current plateau of its anodic polarization curve using a rotating cylinder electrode (RCE). The results show that the electrochemical polishing of PASS is strongly affected by the volume ratio of the mixed acid and the polishing temperature, yet very little by the potentiostatic polishing charge. An optimal brightening and leveling surface of PASS could be achieved by polishing in 2:1 v/v mixed acid at 70 °C. Whereas, polishing in 1:1 and 2:1 v/v ratios at and above 75 °C would result in formation of enlarged pores on the PASS surface due to high dissolution rate within the pores. Pores with rounded edges in the surface morphology of PASS was shown when polishing in 3:1 v/v mixed acid at temperature ranging from 60 to 80 °C. The effects of temperature, acid volume-ratio as well as potentiostatic polishing charge on polishing behavior were discussed based on the results of electrochemical test and the polished surface morphology using scanning electron microscope (SEM). [Copyright &y& Elsevier]

Abstract: Two types of cellular metals were investigated: a closed-cell aluminium foam with a cell size of about 3.5mm and densities ranging from 0.25 to 0.40g/cm3 and hollow sphere structures made of a stainless steel (316L) with sphere sizes of 2 and 4mm and a density of about 0.3g/cm3. Fatigue and fatigue crack propagation tests were performed on these materials using an electro-dynamic resonance fatigue testing machine. The crack extension was monitored by a potential drop technique. Additionally, investigations were carried out inside the scanning electron microscope (SEM) using an in situ loading device. All tests were accompanied by local deformation measurements and fracture surface analyses. From the fatigue crack propagation tests it is evident that these materials show a relatively high Paris-Exponent m in the range of 6 to 25 compared to common ductile solid metals. Additional tests were performed to estimate the influence of crack closure, crack bridging and micro cracking on the da/dN versus ΔK curve for these materials. The in situ fatigue tests and the fracture surface analyses revealed a difference in the fatigue crack propagation mechanisms between the closed-cell foam and the hollow sphere structure: in the closed-cell foam a contiguous fatigue crack can be found, where in the case of the hollow sphere structure the fatigue crack propagation is concentrated in the vicinities of the sintering necks. [Copyright &y& Elsevier]

The effects of SiC particle size and alloy elements such as Si, Cu and Ti on the response to aging treatment and wear resistance in Al-5Mg-X(Si,Cu,Ti)/SiCp composites fabricated by pressureless infiltration method have been investigated by hardness tester, scanning electron microscope (SEM), X-ray diffractometer (XRD), differential scanning calorimetry (DSC) and wear tester. The Al-5Mg-0.3Si-0.1Cu-0.1Ti/SiCP composites had better wear resistance property among Al-5Mg-X(Si,Cu)/SiCP composites. The wear resistance property of all the composites was enhanced after aging at 170°C for 8 hrs due to precipitates of β'(Mg2Si) phase. The wear resistance property of the composite as-fabricated with 50 μm size of SiC particle is superior to that of the composite as-fabricated with 100 μm SiC size of particle. In Al-5%Mg alloy aged at 170°C for 8 hrs, the frictional seizure appeared more than abrading speed of 1.90 m/s, but in Al-5Mg-(Si,Cu,Ti)/SiCP composites aged at 170°C for 8 hrs, the frictional seizure was not found at abrading speed ranging from 0.5 m/s to 4.3 m/s. [ABSTRACT FROM AUTHOR]

A facile method was utilized for the construction of the bioinspired superhydrophobic Mg–Li alloy surfaces with peonylike micronanoscale hierarchical structures. The resultant materials were characterized by scanning electron microscope, x-ray photoelectron spectroscopy, and water contact angle measurements. The obtained Mg–Li alloy surfaces presented the dramatically improved corrosion resistance and long-term stable superhydrophobic properties with a static water contact angle of about 160° and a small sliding angle of less than 5°, which may extend the practical application of Mg–Li alloys in industrial and high-technology fields. [ABSTRACT FROM AUTHOR]