Plasma nitriding is a well‐established technique to improve hardness and tribological properties of austenitic stainless steel. It is proved that it is also possible to preserve the corrosion resistance after nitriding by controlling the process parameters such as time and temperature, obtaining the so‐called S phase. Herein, the corrosion behavior is evaluated for nitrided layers produced by three different plasma treatments: DC plasma nitriding, plasma immersion ion implantation (PIII), and low‐energy ion implantation (LEII), using different parameters in order to obtain the S‐phase in thickness from 1.2 to about 6 μm without nitride precipitation. The microstructure and chemical composition of the nitrided layers is characterized by means of X‐ray diffraction, secondary‐ion mass spectroscopy, and scanning electron microscopy–focused ion beam. The corrosion behavior is evaluated by means of the cyclic polarization tests in NaCl solution. The morphology of the corrosion attack is studied by optical microscopy and SEM‐FIB, revealing a change from crevice to pitting after the nitriding process. The inclusions are observed to be corrosion initiation sites. Due to this, the thickest nitrided layers (with high N concentration) show better corrosion behavior than the thinner ones.

It is undisputed that studying abroad provides several benefits for students, such as improving language knowledge, intercultural awareness, and developing adaptation capacity as well as knowing new ways of learning. Not only does the experience abroad make students grow personally, but in today’s globalized world it can also mean a real advantage for their future professional life [1]. Moreover, the students may have access to research facilities and technical expertise not available at their home university. On the other side, universities profit from their international students since they provide a cultural enrichment for the host university, increase its reputation and international alumni represent a strong potential for future international cooperation. However, additional efforts need to be done both by the students and the university staff in order to organize a study stay abroad and to lead the exchange to a successful experience. Several issues like mobility, teaching, evaluation or recognition of credits may not proceed as smoothly as they should and need further development. The European School of Materials (EUSMAT) at Saarland University has gained vast experience in developing and managing international programs. Recently, a program between Saarland University, the Friedrich-Alexander-University Erlangen-Nurnberg and the Universidad Nacional de Mar del Plata has also been established for the exchange of students in Materials Engineering between Germany and Argentina. This project is supported by the I.DEAR program of the German-Argentinean University Center. In this work we will focus on the benefits and challenges of international study programs based on the example of the cooperation between Argentina and Germany. Therefore, we will present the I.DEAR program by providing statistics of this cooperation and by contrasting the latter with experiences in other programs. The particularities of study systems and possibilities for exchanges between both countries will be discussed.

The objective of this research is to study the influence of microstructure and grinding on the corrosion resistance of ADI in salt water. Immersion and electrochemical tests were performed on samples austempered at two different temperatures and ground. The results indicate that the dissolution rate increases as the nodule count does, and it is also affected by the microstructure and by the surface changes introduced during grinding. A porous layer is formed on ADI-corroded surface due to the selective dissolution of ferrite, and a preferential dissolution of the matrix around graphite is noticeable. Ground surfaces are less corrosion resistant than polished ones.

Surface modification treatments, such as the plasma nitriding improve the tribological properties of AISI 420 stainless steel; however, the corrosion resistance is deteriorated. The DLC (Diamond-Like Carbon) coatings were not only having a low friction coefficient but also good wear and corrosion resistance. In this work, both the corrosion behavior and the adhesion of the DLC hard coating, deposited on nitrided and non-nitrided AISI 420 stainless steel substrates, were studied. The coatings were characterized by means of EDS and Raman. In addition, nitrided layer microstructure and the coatings were analyzed by SEM-FIB and XRD. Corrosion behavior was evaluated by the salt spray fog test and cyclic potentiodynamic polarization tests in NaCl solution. The adhesion was assessed using Rockwell indentation and scratch tests. The a-C:H film and nitrided layer thicknesses were about 2.5 μm and 11 μm respectively. The nitrided layer improved adhesion in both tests. The coated AISI 420 stainless steel proved to have excellent atmospheric corrosion resistance and a passive behavior over 1 V (versus SCE) in the electrochemical tests. The adhesion and the corrosion performance were improved when the coating was deposited after the plasma nitriding treatment.

Stainless steels are widely used in chemical, petrochemical and food-processing industries due to their good anticorrosion properties. However, they generally exhibit poor tribological properties which limit their applications in tribocorrosive conditions. Surface modifications, like diamond-like carbon (DLC) coatings, can be an optimal technological solution to overcome this problem. These films have attracted considerable attention because of their outstanding mechanical and tribological properties, but they have a major drawback that is their high internal stresses and low thermal stability. The internal stresses and film hardness depend on the ratio sp2/sp3, therefore, the film can be classified as hard or soft-DLC coatings depending on this ratio. In this work, different stainless steels (EN14301, EN14435 and EN12316) samples were DLC-coated by plasma assisted chemical vapor deposition. Hard and soft a-C:H:Si films (silicon containing amorphous hydrogenated carbon) were obtained. The films were characterized by wear and adhesion tests; the results show an increase of the practical adhesion at higher film thickness and this improvement would be more effective for harder substrates. Pin-on-disc tests showed that soft-DLC films tend to develop a better tribological behavior than hard-DLC films and it is not influenced by the film thickness or the type of stainless steel substrate. The influence on the tribological behavior of test parameters, such as slide velocity and load, varies with the coating type.

Precipitation hardening stainless steels are used in applications where wear and corrosion resistance are required. To improve the surface properties, thermochemical treatments in combination with hard coatings can be used. In this work, the corrosion behaviour of SiOxNy coatings deposited on nitrided and non-nitrided Corrax(R) PH stainless steel were evaluated comparing them with the behaviour of samples which were only nitrided (two different conditions of nitrogen percentage in the working gases were used).The microstructure was analyzed. Corrosion behaviour was evaluated by the Salt Spray Fog Test and cyclic potentiodynamic polarization in NaCl solution. Erosion-corrosion tests were conducted.The thickness of the coating was about 1.4 microns, and its hardness was 2300 HV. The film had better erosion and corrosion behaviour when it was deposited on the nitrided steel. This fact demonstrated that the nitrided layer results in a good interface that improves the adhesion and mechanical support. (C) 2015 The Authors. Published by Elsevier Ltd.

An electrical model able to decouple the electron pathway from microbial cell machinery impedance terms is introduced. In this context, capacitance characteristics of the biofilm are clearly resolved. In other words, the model allows separating, according to the advantage of frequency and spectroscopic response approach, the different terms controlling the performance of the microbial biofilm respiratory process and thus the directly related electricity production process. The model can be accurately fitted to voltammetry measurements obtained under steady-state conditions and also to biofilm discharge amperometric measurements. The implications of biological aspects of the electrochemical or redox capacitance are discussed theoretically in the context of current knowledge with regard to structure and physiological activity of microbial Geobacter biofilms.

Plasma assisted surface modification methods have been used to nitride stainless steels in order to enhance hardness and therefore the lifetime of industrial components. Nevertheless, the corrosion resistance is not always preserved since it is very sensitive to the process parameters, either in implantation or in thermochemical diffusion techniques. AISI 316L stainless steel was plasma nitrided using three different techniques: Low Energy Ion Implantation (LEII), Plasma Immersion Implantation (PI3) and conventional DC pulsed plasma nitriding (DCPN). For each method several parameters were tested and some of them were selected to achieve the so called S phase of about 3 µm thickness and no nitrides precipitation. The nitrided layer was characterized with OM and SEM. Hardness was assessed on the surface with Vickers indenter and 25 g load. XRD was performed to characterize the S phase and to detect other phases if present and electrochemical corrosion tests were carried out in 3.5% NaCl solution. Although the S phase thickness in the three groups of samples was comparable, hardness was not and neither was the corrosion resistance. The PI3 samples were the hardest with the best performance in corrosion experiments, resulting in a higher breakdown potential and lower currents.

Abstract UNS 31603 austenitic stainless steel was nitrided using different techniques, and pitting corrosion resistance was analysed in a chloride solution. All nitriding techniques, LEII, PI· and convectional DC nitriding produced a nitrided layer called S phase which is corrosion resistant. Pits morphology and layer structure was investigated using optical and electronic microscopy, SEM-FIB, EDS, and a 3D reconstruction of a pit was assessed using FIB tomography. It was concluded that pits are initiated in MnS inclusions and a channel was generated passing through the nitrided layer, connecting the steel with the electrolyte. Base alloy dissolution was observed beneath the nitrided layer.

The corrosion behavior of Cu-Al-Be shape memory alloys with different microstructures and Be content in a 3.5% NaCl solution was studied by weight loss, cyclic, anodic polarization and chronoamperometric measurements. The beryllium has a beneficial effect in beta alloys. A pitting potential of -100 mV/SCE was found by anodic polarization tests for all the studied alloys, corresponding to the formation of pits produced by severe dealuminization. Samples with precipitates were more susceptible to pit formation. The corrosion behavior is strongly affected by the alloy microstructural conditions, and the beta samples present higher pitting resistance and repassivation ability. (C) 2013 Elsevier Ltd. All rights reserved.

Austenitic stainless steels are the preferred materials for mechanical components in the food, oil and chemical industries due to their good corrosion resistance but they often suffer severe wear due to their poor tribological properties. Plasma surface engineering has been extended to stainless steel hardening, through the modification of the surface with ion nitriding or the application of hard coatings.

One of the most employed methods for CO2 corrosion control in oil and gas production and transportation industry is the use of carbon and low alloy steels in conjunction with corrosion inhibitors. The inhibitor performance can be influenced by the microstructure and chemical composition of the steel. In previous works, it was shown that 1% Cr addition to carbon steel decreased the protectiveness of a commercial imidazoline-based inhibitor. However, it was suspected that changing the flow rates may modify the inhibitor behaviour. In the present work, the performance of an imidazoline-based inhibitor was investigated on two carbon steels one with the other without 1% Cr, under different flow rates. Corrosion and corrosion inhibition experiments were carried out using a rotating cylinder electrode at different rotation speeds in a deoxygenated 5 wt.% NaCI CO2-saturated solution at 40 degrees C, pH 6 with and without inhibitor addition. Electrochemical measurements were taken during each experiment and sample surfaces were analyzed after each experiment. Inhibitor performance was found to be dependent on flow velocity and chemical composition of carbon steel. (C) 2012 Elsevier B.V. All rights reserved.

A study has been conducted to analyze the influence of 1% Cr additions, microstructure, and pre-corrosion on the performance of CO2 corrosion inhibitors for C-Mn steels. Two carbon steels with two different microstructures were tested in a deoxygenated 5 wt.% NaCl solution, saturated with CO2 at 40 degrees C, pH 6. An imidazoline-based inhibitor was added after different pre-corrosion periods. Its performance was studied by means of d.c. electrochemical measurements, SEM and EDS. The results demonstrated a detrimental effect of 1% Cr and pre-corrosion on the inhibitor efficiency. It was also proven that the impact of precorrosion depends on microstructure and chemical composition. (c) 2010 Elsevier B.V. All rights reserved.

The corrosion products formed on a multiphase Cu-11.40Al-0.55Be (wt.%) alloy in 3.5% NaCl at open circuit potential, and their evolution with immersion time were studied mainly by micro-Raman and in situ AFM measurements. The aluminium content of each phase affects the formation of the corrosion products on them. After 1 day of immersion, gamma 2 precipitates were more susceptible to dealuminization, while alpha' phase exhibited a high corrosion stability. The corrosion products evolved with immersion time, and CuCl(2) and a Cu(2)O/CuO double layer film were the stable products formed on all the phases after long times. (C) 2011 Elsevier B. V. All rights reserved.

The corrosion inhibition mechanism of the N-[2-[(2-aminoethyl)amino]ethyl]-9-octadecenamide on mild steel surface in CO2-saturated 5% NaCl solution has been studied. The inhibition efficiency decreases with increasing temperature. Adsorption of the inhibitor studied is found to follow the Frumkin adsorption isotherm. EIS results show that the mechanism of its corrosion inhibition at concentrations higher than critical micelle concentration is by forming a protective porous bi-layer. The activation energy, thermodynamic parameters and electrochemical results reveal a change in the adsorption mode of the inhibitor studied: the inhibitor could primarily be physically adsorbed at low concentrations, while chemisorption is favoured as concentration increases. (C) 2011 Elsevier Ltd. All rights reserved.

The corrosion behavior of mild steel in CO2-saturated 5% NaCl solution with N-[2-[(2-aminoethyl) amino] ethyl]-9-octadecenamide corrosion inhibitor at 25 °C has been studied by using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and Polarization Modulation Infrared Reflection Absorption Spectroscopy (PM-IRRAS) measurements. Both potentiodynamic polarization and EIS measurements reveal that this amido-amine precursor inhibits the carbon steel corrosion and the inhibition efficiency increases with increasing the inhibitor concentration. The corrosion inhibitor exhibits high corrosion efficiencies as a mixed-type inhibitor, with a predominant influence on the anode process. The organic inhibitor acts blocking surface sites at low concentrations and by modifying the adsorption mechanism forming a protective barrier against corrosive ions at high concentrations. EIS results show that the mechanism of its corrosion inhibition at concentrations higher than 0.82 × 10−5 M is by forming a protective bilayer with small pore sizes that hinders the passage of the reactive species. PM-IRRAS measurements demonstrate that the inhibitor is chemisorbed to surface steel. Therefore, its spectrum reveals that the inhibitor monolayer has an amorphous structure.

The influence of the microstructure on the corrosion behaviour of a shape memory Cu-11.40Al-0.55Be (wt.%) polycrystalline alloy in 3.5% NaCl has been studied by microscopical examinations, spectroscopical and X-ray diffraction measurements, and electrochemical tests. Chloride environment can produce a dealuminization attack, and the corrosion behaviour is affected by the alloy microstructural conditions. After long times of immersion, the single beta phase microstructure suffers localized corrosion in some regions but dealuminization is generalized on the whole surface. However, in the (beta + gamma(2)) microstructure, preferential dissolution of gamma(2) dendritic precipitates occurs, which seems to protect beta matrix from dealloying. (C) 2010 Elsevier B. V. All rights reserved.

In this work we report the results of a combined biochemical and electrochemical study aimed to analyze both the growth of biofilms of Pseudomonas fluorescens on copper samples and its possible role in the instability of the metal/electrolyte interface. DNA and RNA were quantified along the time for biofilms grown on copper and glass to estimate both the growth of the bacterial population and its metabolic state (through the RNA/DNA ratio). The expression and specific activity of catalase were also determined to gain insight into their possible role in corrosion acceleration. The electrochemical behavior of the biofilm/copper interface was monitored by Linear Polarization Resistance (Rp) and electrochemical impedance spectroscopy (EIS) along the experiments. Results showed a longer lag phase for biofilms developing on copper that included a period of high metabolic activity (as measured by the RNA/DNA ratio) without biomass growth. Biological activity introduced a new time constant at intermediate frequencies in EIS spectra whose capacitive behavior increased with the biofilm development. The increment in this biofilm-related signal was accompanied by a strong limitation to charge transfer through a diffusion controlled process probably due to oxygen exhaustion by cells respiration, while the resistance of the interface decreased presumably due to oxide dissolution by local acidification under the colonies. In addition, catalase activity was found to be high in mature copper-tolerant biofilms, which differentially express a catalase isoform not present in biofilms growing on glass.