The corrosion behaviour of AISI 420 martensitic stainless steel, frequently employed in dental prosthetics due to its mechanical strength and cost-effectiveness, necessitates a thorough and multidimensional investigation. While this steel offers advantageous machinability, its lower corrosion resistance compared to that of austenitic steels raises concerns, particularly when influenced by factors such as inclusions, residual stresses, and contamination from machining processes. This study aims to elucidate the causes of pitting corrosion on prosthetic keys fabricated from AISI 420. It highlights critical manufacturing stages, particularly washing and passivation processes, which are vital for mitigating corrosion risks. Experimental analyses revealed that corrosion initiation can be attributed to metal residues, inadequate passivation, and contaminated washing water. Furthermore, it was determined that the presence of rust is more closely associated with improper storage and drying practices than with inherent material defects. These findings underscore the importance of meticulous handling and verification of prosthetic components prior to packaging and highlight the need for standardised procedures during sterilisation in clinical settings. The outcomes of this research contribute significantly to enhancing the longevity and reliability of dental prosthetic applications, emphasising the necessity for technological interventions to prevent corrosion in clinical environments.

Sandblasting materials used for dental restoration are a valuable preconditioning technique that enhances the physical properties and promotes osseointegration and cell adhesion. Triplicate groups of Ti medical grade 4 and Ti6Al4V were blasted with 16 series of various naturally occurring and synthetically produced spraying materials of controlled granulometry at three spraying durations each and two spraying pressures, and the results were tested for the determination of the surface roughness taken as an average of 80 points ±5 points for each particular series of operating parameters. SEM analysis and specific tests to see whether or not cell cultures proliferate on the treated materials were also conducted. It was found that in all cases, regardless of the spraying material or working conditions, the roughness profile achieved is a uniformly distributed one. A reduction in the blasting pressure by half led to a decrease in the roughness between 30 and 35%. The use of glass balls as blasting material led to decreased roughness and more uniformly distributed roughness values for Ti as well as for Ti6Al4V, regardless of spraying duration or applied pressure compared to other spraying materials. Blasting with olivine led to increased, as well as uniformly distributed, values, and hence the conclusion that one may control the roughness size by choosing one or another of the above materials without the need to change any other operating parameters. In the case of Ti, the achieved roughness is greater than in the case of Ti4Al6V, regardless of the blasting material; the differences are smaller the softer the sandblasting material due to the fact that Ti alloys have better mechanical properties and increased hardness compared to pure Ti. SEM analysis showed that the use of sintered hydroxyapatite as an additive to the blasting material does not necessarily lead to a substantial deposition of hydroxyapatite on the substrate materials; only traces of it were identified during the analysis. As a general conclusion, this study showed that by sandblasting Ti and Ti6Al4V with different spraying materials, one may control the surface roughness, and this technique may be an attractive method for preconditioning these materials for restorative dentistry.

Carbon steel is one of the most common alloys employed in a multitude of industries. However, it has low corrosion resistance and some methods were used in order to enhance the anticorrosion properties, such as modifying the composition of the steel by further alloying, deposition of protective layers on the substrate or modifying the aggressive media by adding corrosion inhibitors. This paper presents the results of adding an environmental friendly extract (Citrus x clementine) in the aggressive media on the corrosion of steel. Methods such as open circuit potential, electrochemical impedance spectroscopy and polarisation for corrosion (Tafel) were employed in order to determine the influence of the Citrus x clementine leaves extract on the corrosion rate of steel in 3.5%NaCl. The results presented in this paper provide useful information on the stability of carbon steel in the modified aggressive media and on the polarisation resistance and corrosion rate of carbon steel in 3.5% NaCl, and in 3.5% NaCl modified with Citrus x clementine extract in concentrations from 50?L - 600?L.

The anodization or thermal treatments applied to alloys of titanium and zirconium have a substantiated effect on the mixed-oxide layer formation compared to the naturally occurring one. A Ti–Zr 50%/50% alloy was chosen for a comparative study. Controlled, thermally treated, and anodized samples obtained with controlled procedures were analyzed in terms of morphological and compositional analysis (using SEM and EDX analysis) as well as for the determination of hardness variations. Substantial differences were observed depending on the applied functionalization method (compact of structured mixed-oxide nanotubes when the samples are subjected to the anodization procedure); there was an increase of more than six folds in the mixed-oxide layer hardness and D Shore scale, when subjected to thermal treatment, and hence, this lead to the conclusion that one may control the morphology, composition and/or the hardness of the mixed-oxide layer by applying one or another or a combination of functionalization methods.

This paper presents the influence of natural extracts obtained from Levisticum officinale and Citrus x clementine on the corrosion of carbon steel in a 3.5% NaCl solution. We started from dried leaves of Levisticum officinale and Citrus x clementine peel in order to prepare several extracts in a 50%:50% (v:v) water/ethanol solution and in analytical-grade ethanol. Several electrochemical techniques, such as open circuit potential monitoring, electrochemical impedance spectroscopy and potentiodynamic polarization, were employed in order to investigate the influence of the synthetized extracts on the corrosion of carbon steel. The aggressive solution that the corrosion tests were performed in was a 3.5% NaCl solution modified with different amounts of the extracts. The electrochemical tests performed in order to determine the influence of the Levisticum officinale leaf and Citrus x clementine peel extracts showed that these extracts may be employed as natural corrosion inhibitors for carbon steel in a 3.5% NaCl solution, achieving inhibiting efficiencies up to 87.8%, in the case of the Levisticum officinale extracts.

This study outlines the improvement on anticorrosion behavior of chitosan-based sol-gel coatings on carbon steel surface obtained for high deacetylation degree values of this natural biopolymer. Important economic losses in major industries represent a problem due to corrosion of metals in aggressive medium, such as carbon steel, which is widely used due to its hardness, durability, ductility, low cost, handiness. Therefore, non-toxic, cost-effective, and eco-friendly strategies are needed to protect metallic surface of steel. Against this background, the anticorrosion coating performance of chitosan, from three different commercial sources, as a single component, on carbon steel in chloride solutions is investigated using electrochemical impedance spectroscopy technique. The present study is performed to evaluate the corrosion protective abilities of chitosan in order to determine the relationship with its deacetylation degree (DDA), evaluated by potentiometric titration, a simple and reliable method. Depending on the DDA, the experimental results indicate that there is a remarkable difference between different chitosan samples regarding the value of the charge transfer resistance of coating on steel.

The paper presents preliminary studies of the corrosion behavior in NaCl solution of a composite made up of a conversion coating of alumina obtained by sulphuric anodization and chitosan biopolymer. The results obtained from the electrochemical studies (potentiodynamic polarization, electrochemical impedance spectroscopy) indicate a decrease of the corrosion current density for alumina-chitosan composite and a corrosion resistance improvement comparing to untreated aluminum. The presence of the alumina-chitisan composite stabilizes the passivation behavior of the anodized samples due to the sealing of the alumina pores with chitosan biopolymer.

This paper presents the results achieved for the reconditioning of some lithium-ion batteries that were considered inappropriate for usage in their applications. In order to evaluate the efficiency of the reconditioning procedure, one has calculated a reconditioning degree (g(r)), which indicates the percentage of the rechargeable battery recovered capacity versus its nominal capacity. This procedure shows promising results for structural sound intact batteries and one may see that after the reconditioning process, the recovered capacity of the lithium-ion batteries may reach up to 95% of its initial capacity stated in the technical specifications. The results obtained indicate that the recondition of lithium-ion is a procedure which may be introduced as an alternative way for recycling, this procedure allowing the reintroduction of these batteries to their originally intended use decreasing the amount of rechargeable lithium-ions batteries that end up to recycling, as well as decreasing the market demand and saving valuable metals used for their manufacture.

The corrosion of mild steel and Al alloy in Fomtec P 6% and 6% P Profoam 806 protein-based foam concentrates was investigated. Weight-loss data for steel showed corrosion penetration of 0.745 mipy in Fomtec and 2.269 mipy in Profoam, whereas for Al alloy the penetration levels were 0.474 and 1.093 mipy, respectively. Scanning electron microscopy and energy dispersive X-ray spectroscopy allowed characterization of the metallic surface covered or free from corrosion products. Values of corrosion potential, corrosion current density and corrosion penetration were calculated by using potentiodynamic polarization curves. Electrochemical impedance spectra illustrated the change in polarization resistance during anodic polarization. Data obtained by accelerated electrochemical methods confirm the greater aggressiveness of the Profoam concentrate compared to Fomtec concentrate.

Most dental implants used in dental practices are made of titanium or titanium alloys so that the essential differences promoted by the various manufacturers are at the level of their surface; through specific surface treatments, the aim is to obtain improved results regarding osseointegration. This study attempts to identify the differences between a series of used brands of dental implants by analyzing the chemical composition and the morphology of their surface and is particularly significant for the potential users as it highlights the manner of performances of the aforementioned implants, providing them with a tool in choosing the proper dental implant to suit their needs. It was found that, as the technology evolved and the costs were reduced, there is a net preference for using pure titanium or its alloys in the manufacture of dental implants versus the stainless steel titanium alloys, considered now a thing of the past.

In this paper, two case studies regarding the application of a reconditioning procedure of aged lithium-polymer batteries used to power a notebook and a tablet are presented. The parameters measured in the evaluating the performance of the reconditioned rechargeable batteries are the charging/discharging capacity and the internal resistance. The results obtained indicate a high degree of reconditioning of the investigated batteries, expressed as a reconditioning coefficient, calculated on the basis of the measured nominal capacities after applying the reconditioning procedure with respect to the initial one.

The influence of temperature and heating time on the decarboxylation of Delta(9)-tetrahydrocannabinolic acid (Delta(9)-THCA) and cannabidiolic acid (CBDA) of some seized cannabis inflorescences was studied in this work. The results showed that the decarboxylation rate increases with increasing temperature, especially in the temperature range between 75 and 150 degrees C for Delta(9)-THCA, respectively 100 and 175 degrees C for CBDA. The maximum value for Delta(9)-THC recorded throughout the temperature range at which the experiments were performed was found to be approximately constant. This result suggests a nearly complete conversion of Delta(9)-THCA to Delta(9)-THC. The decarboxylation of CBDA does not seem to proceed completely to CBD, the results obtained indicating the possibility that some secondary compounds may also be the product of this transformation.

This paper presents the results obtained during the electrogeneration of active chlorine species. Active chlorine species were generated through the electrolysis of sodium chloride solutions in an undivided cell, employing two platinised platinum electrodes and a polarity reversal procedure. The electrolytic process was conducted at four current densities (0.05, 0.10, 0.30 and 0.50 A/cm2) and three concentrations (0.1, 0.5 and1 mole/L) the polarity reversal period being of 5 min. The brine flow rate was kept constant, namely 1.68 L/h. The results showed a maximum active chlorine concentrations for an initial brine concentration of 0.5 mole/L. The overall concentration of dissolved chlorine in water was quantified as active chlorine, defined as the sum of the three possible species (Cl2, HClO and ClO-).

Comparative studies regarding gold electroplating accomplished on carbon steel electrical contacts using a toxic electrolyte that contains sodium dicyanoaurate (I), as well as a non-cyanide electrolyte were presented in this paper. In order to determine if the substitute electrolyte can be considered equally suitable to replace the cyanide toxic electrolytes, several comparative analyses of gold thin deposits and a series of characterization methods such as: Scanning Electron Microscopy (SEM) for morphological structure investigation, Energy-Dispersive X-ray Spectroscopy (EDS) for quantitative analyses of the deposits, and Elemental Mapping for the element distribution, were performed. It has been found that gold thin films on a nickel intermediate layer from sulphite electrolyte baths present superior properties being accomplished in a shorter processing time with no effects on operators' health and on the environment.

Nickel-Copper metallic layers were deposited onto a steel substrate by using the electrochemical method. The morphology and the chemical composition of the deposited layers were studied by scanning electron microscopy. The electrical capacitance was measured on a functional supercapacitor made of two Ni-Cu deposited layers and a Nafion 117� membrane hydrated with distilled water, which served as a dielectric separator.

This paper discusses the properties of some Ni-Cu deposits obtained on a steel substrate, which may be employed as supercapacitor plates. In order to achieve plates with different properties, one has varied the parameters of the deposition process such as deposition time, current density and temperature. Scanning electron microscopy and dispersive energy spectrometry were employed for the determination of the structure and composition of the Ni-Cu deposits. The plates with the Ni-Cu deposits were used to create supercapacitors and their capacitance values were also determined.

This paper presents the characterization of a Ni-Cu thin layer electrodeposited onto a steel substrate. The characterization of these films was performed with X-ray diffraction spectroscopy, Raman spectroscopy and Scanning electron microscopy. The results of the XRD analysis showed a Face Centered Cubic structure and the Raman spectroscopy indicated the presence of Cu2O, CuO and NiO into the films.

In this paper the properties of some Ni-Cu layers deposited onto a steel substrate were discussed. One has investigated the influence of the electrodeposition process on the final properties of the Ni-Cu layers, in order to see if these electrodeposited layers could be used as supercapacitor plates. The structural characterization was investigated by scanning electron microscopy and their composition by dispersive energy spectrometry. One has built a number of functional supercapacitors using Ni-Cu layer plates inserting in between them a separation membrane and their capacitance values were determined.

This paper introduces a method of reconditioning lithium-polymer batteries which are no longer performing as expected. The reconditioning process consists of consecutive charging/discharging steps at controlled currents and is followed by an evaluation procedure, in order to determine the actual performances of the reconditioned batteries. For the evaluation of the characteristics of the Li-polymer batteries, one has measured the charging capacity, the discharging capacity and the internal resistance. However, after the reconditioning stage, one must look for a new application for these batteries, as the reconditioned batteries are seldom behaving as the new ones to be used for the same initial designated application. We manufactured and tested a cold jump-start system, particularly useful in the case of cars flat batteries or cars batteries starting failure. The advantages of this system consist in their reduced mass and volume and a very powerful starting current, comparable to that of high capacity lead acid batteries, the system being able to act as multiple starting aids.