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Corrosion inhibitors represent one of the most commonly used methods for significantly reducing the corrosion rate of metals and alloys. Adsorption inhibitors have a wide range of applications in cooling water systems, deicing solutions for aircrafts, airports and ways, etching and degreasing solutions, oil pipelines, paints and coatings and metal processing solutions. Adsorption corrosion inhibitors of metals and alloys are generally organic compounds that contain structures with heteroatoms (N, P, S, As, O) in their molecules, having lone pair electrons or π electrons in aromatic rings or multiple bonds. They enable relatively strong interactions between the metal atoms and organic molecules, resulting in a protective layer of organic molecules adsorbed at the metal-corrosive solution interface. Most molecules of active substances from drugs contain similar structures, which is why many drugs have been already tested as corrosion inhibitors. One of the major disadvantages of using drugs for this purpose is their particularly high price. To overcome this impediment, the possibility of using expired drugs as corrosion inhibitors has been investigated since 2009. The present paper is an exhaustive compilation of the scientific published papers devoted to the use of expired drugs as corrosion inhibitors in various aggressive solutions. The inhibitory efficiencies of expired drugs are presented as a function of the studied metal or alloy and the nature of the aggressive solution, as well as the concentration of the inhibitor in such a solution. Research has especially been focused on mild and carbon steel and less on stainless steel, as well as on some metals such as copper, zinc, nickel, tin and aluminum and its alloys. The experimental methods used to assess the inhibitory efficiencies of expired drugs are briefly discussed. Also, the available information on the stability of the active substances in the drugs is presented, although most authors were not concerned with this aspect. Finally, several actions are revealed that must be undertaken by researchers so that the results obtained in the study of the anticorrosive action of expired drugs can be applied at the industrial level and not remain only an academic concern.

Here, potential metallic bipolar plate (BP) materials were manufactured by laser coating NiCr-based alloys with different Ti additions on low carbon steel substrates. The titanium content within the coating varied between 1.5 and 12.5 wt%. Our present study focussed on electrochemically testing the laser cladded samples in a milder solution. The electrolyte used for all of the electrochemical tests consisted of a 0.1 M Na 2 SO 4 solution (acidulated with H 2 SO 4 at pH = 5) with the addition of 0.1 ppm F - . The corrosion resistance properties of the laser-cladded samples was evaluated using an electrochemical protocol, which consisted of the open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) measurements, and potentiodynamic polarization, followed by potentiostatic polarization under simulated proton exchange membrane fuel cell (PEMFC) anodic and cathodic environments for 6 h each. After the samples were subjected to potentiostatic polarization, the EIS measurements and potentiodynamic polarization were repeated. The microstructure and chemical composition of the laser cladded samples were investigated by scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX) analysis.

Cost reduction in bipolar plates in proton exchange membrane water electrolyzers has previously been attempted by substituting bulk titanium with austenitic stainless steels protected with highly conductive and corrosion-resistant coatings. However, austenitic steels are more expensive than ferritic steels due to their high nickel content. Herein we report on the corrosion resistance of two high chromium ferritic stainless steels, AISI 442 and AISI 446, as an alternative material to manufacture bipolar plates. Electrochemical corrosion tests have shown that AISI 442 and AISI 446 have similar corrosion resistance, while AISI 446 reveals more noble corrosion potential and performs better during potentiostatic stress tests. The current density obtained during polarization at 2 V versus the standard hydrogen electrode (SHE) is 3.3 mA cm -2 , which is more than two times lower than on AISI 442. Additionally, surface morphology characterization demonstrates that in contrast to AISI 442, AISI 446 is not sensitive to intercrystalline or pitting corrosion. Moreover, EDX energy dispersion analysis of AISI 446 reveals no differences in the chemical composition of the surface layer compared to the base material, as a confirmation of its high corrosion resistance. The results of this work open up the perspective of replacing austenitic stainless steels with less expensive ferritic stainless steels for the production of components such as bipolar plates in proton exchange membrane water electrolyzers., Competing Interests: The authors declare no conflict of interest.

In this work, the corrosion behavior of NiCr(Ti) protective coatings deposited on mild steel substrates through laser cladding technology is studied as an alternative new material for metallic bipolar plates used in PEMFC applications. For electrochemical testing, a solution consisting of 0.5 M H 2 SO 4 + 2 ppm F - at room temperature is used as an electrolyte. The fluoride ions are added to simulate the conditions in the PEM fuel cell due to degradation of the proton exchange membrane and fluoride release. A saturated calomel electrode (SCE) is used as a reference electrode and a platinum mesh as the counter electrode. Scanning electron microscopy (SEM) and optical microscopy (OM) are used for studying the morphology of the protective coatings and the effect of Ti addition. The electrochemical evaluation consisted of measuring the open circuit potential (OCP), followed by electrochemical impedance spectroscopy measurements (EIS) and potentiodynamic polarization. It is found that the coatings with 5% Ti, 7% Ti and 10% Ti addition comply with the conditions of the US DOE regarding corrosion performance to be used as materials for the manufacture of the bipolar plates.

The current work explores the potential for recycling unused or expired Midazolam (MID) drug, a benzodiazepine derivative, as an efficient corrosion inhibitor for copper in nitric acid solution. The technical advantage of recycling expired MID drug relates to the avoidance of organic inhibitor production costs and the reduction of disposal costs of the expired medication. A combination of electrochemical methods (potentiodynamic polarization and electrochemical impedance spectroscopy), weight loss, and quantum chemical calculation were used to assess the inhibition mechanism and efficiency of MID. It was found that inhibition efficiency increases with inhibitor concentration, reaching a highest value of 92.9% for a concentration of 10 -4 M MID. MID was classified as a mixed-type inhibitor, showing a preferential cathodic suppression mechanism. The obtained values of -45.89 kJ mol -1 for the standard free energy of adsorption indicate that the inhibition mechanism is based on chemisorption of MID molecules on the copper surface, which obeys the Langmuir isotherm. Surface analysis using scanning electronic microscopy revealed that MID offers high protection against corrosion during both immersion and polarization tests. Molecular modelling and quantum chemical calculations indicated chemical interactions between MID molecules and the copper surface, as well as electrostatic interactions. The results obtained using the different techniques were in good agreement and highlight the effectiveness of MID in the corrosion inhibition of copper.

For proton exchange membrane water electrolysis (PEMWE) to become competitive, the cost of stack components, such as bipolar plates (BPP), needs to be reduced. This can be achieved by using coated low-cost materials, such as copper as alternative to titanium. Herein we report on highly corrosion-resistant copper BPP coated with niobium. All investigated samples showed excellent corrosion resistance properties, with corrosion currents lower than 0.1 µA cm -2 in a simulated PEM electrolyzer environment at two different pH values. The physico-chemical properties of the Nb coatings are thoroughly characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). A 30 µm thick Nb coating fully protects the Cu against corrosion due to the formation of a passive oxide layer on its surface, predominantly composed of Nb 2 O 5 . The thickness of the passive oxide layer determined by both EIS and XPS is in the range of 10 nm. The results reported here demonstrate the effectiveness of Nb for protecting Cu against corrosion, opening the possibility to use it for the manufacturing of BPP for PEMWE. The latter was confirmed by its successful implementation in a single cell PEMWE based on hydraulic compression technology.

To enhance the sliding wear and corrosion behavior of steels with low carbon content, cermet composite coatings are usually deposited on their surface by various deposition processes. Laser cladding, compared to other deposition techniques such as electroplating, arc welding, and thermal spraying, has numerous advantages to produce such protective coatings. The paper presents the optimization of laser cladding deposition speed versus energy density in order to obtain WC-Co/NiCrBSi coatings with Ni-Al addition free of defects and reduced porosity deposited on low carbon steel substrate. The microstructure and chemical composition were investigated by SEM combined with EDX analysis while XRD was performed in order to examinate the phases within the coatings. In order to investigate the cladding speed influence on the coatings, hardness measurements, POD (pin on disk) wear tests and corrosion tests in 3.5% NaCl solution were carried out. The results showed that an optimal cladding speed has a crucial impact on the microstructure, composition, and hardness. It was found out that optimizing the cladding deposition speed proved to be effective in enhancing the sliding wear resistance and corrosion behavior by controlling the iron content within the coatings.

Due to the large quantity of expired and unused drugs worldwide, pharmaceutical disposal has become a serious problem that requires increased attention. In the present paper, the study on recycling ceftazidime (CZ) as an additive in copper and nickel electrodeposition from acid baths is highlighted. CZ is the active substance from expired commercial drug Ceftamil ® . Its electrochemical behavior was studied by cyclic voltammetry. As well, kinetic parameters for copper and nickel electrodeposition were determined using Tafel plots method at different temperatures and CZ concentrations in these acid baths. The activation energy was calculated from Arrhenius plots. Electrochemical impedance spectroscopy was used to investigate the charge transfer resistance and coverage degree in the electrolyte solutions at several potential values. Gibbs free energy values, calculated from Langmuir adsorption isotherms, revealed the chemical nature of CZ-electrode surface interactions. The favorable effect of the organic molecules added in copper and nickel electroplating baths was emphasized by optical microscope images. The morphology of the obtained deposits without and with 10 -4 mol L -1 CZ was compared. The experimental results revealed that expired Ceftamil ® is suitable as additive in copper and nickel electroplating processes from acid baths.

Supplying food to growing human populations without depleting natural resources is a challenge for modern human societies. Considering this, the present study has addressed the use of native arboreal species as sources of food for rural populations in the Brazilian Atlantic Forest. The aim was to reveal species composition of edible plants, as well as to evaluate the practices used to manage and conserve them. Ethnobotanical indices show the importance of many native trees as local sources of fruits while highlighting the preponderance of the Myrtaceae family. Conservation analysis allowed to identify Campomanesia hirsuta Gardner and Plinia edulis (Vell.) Sobral as being of high Biological Value and Conservation Priority. In spite of that, the local management practices of native fruits appear to be sustainable and contribute to the maintenance and dissemination of valuable species. These results suggest a number of recommended future conservation actions and show the potential of Myrtaceae species for future agronomical development in Neotropical regions.