Portugaliae
Electrochimica Acta

The aim of this manuscript was to optimize the IE(%) of a pyridazine derivative (MDP) for hindering MS corrosion in a 1 M HCl solution. To identify the most influential parameters affecting CI, a study was conducted using a Doehlert matrix and Nemrod software. Based on preliminary knowledge, three parameters (Ct from MDP, IT and T) were selected. IE(%) was evaluated by analyzing PDP intensity-potential curves and interpreting the obtained results. The novelty of this research stems from the methodical application of DoE methodology to optimize CI, which offers notable advantages such as reduced test requirements, and the ability to discern interactions between factors. The findings revealed a remarkable IE(%) of 96%, under optimal conditions: Ct from MDP of 0.3 x 10-3 mol/L, IT of 12 h and T of 303.15 K. Keywords: corrosion; DoE; inhibition; MDP; MS; PDP.

MS is the most commonly used alloy in industries, due to its remarkable features such as high thermal requirements, low cost, easy availability, high strength, durability and electrical conductivity. In recent years, scientists have focused on green inhibitors obtained from plants, fruit extracts and essential oils. Besides being environmentally friendly, in terms of corrosion resistance, plant extracts are becoming increasingly important, due to their low cost and toxicity, and high availability. Additionally, they are rich in organic compounds with polar atoms, such as O, P, S and N, containing multiple bonds in their molecules, through which they can adsorb onto the metal surface, forming a protective film, by various adsorption isotherms. This paper provides a review on research works done on MS corrosion control by naturally occurring plant extracts as corrosion inhibitors in H2SO4 solutions. Keywords: corrosion inhibition; EIS; H2SO4; MS; plant extracts; PDP; WL.

The background motivation of this paper was SPP, which refers to surface waves occurring at terahertz frequencies, as widely used wave in optics industry. This wave has been produced during the electromagnetic field interaction with oscillations of free metal electrons. Due to their improved field and intense incarceration close to the metal surface, SPP waves have been extensively employed for high sensitivity sensors and small photonic circuits. The method herein proposed was a BPF based on designer-SPP by means of central frequency and adjustable bandwidth. It was adjusted via varactor diodes placed in different positions in the T-shaped resonator. Considering the constraints and strengths of high field SPP polarizations, hearing and coupling becomes weaker than that from the usual microstrip. Analytical and evaluation methods comprised three inductors assessed at different locations of the T-shaped resonator, which were controlled by DC bias voltage. Transition from the microstrip QTEM mode to SPP misleading mode was performed to excite SSPP based on the T-shaped resonator with g-distance coupling. Keywords: adjustable central frequency; BPF; QTEM, SPPP.

This study investigated the electrochemical performance of pure Al and Al alloy anodes in Sw environments for CP real-world applications, such as marine environments, under various operational conditions. Experimental results showed a significant activation of Al alloy anodes compared to pure Al, as indicated by a more anodic shift in OCP and a marked increase in jcorr. The impact of varying DAC and changes in Sw conductivity on CP performance was also herein explored. These factors notably influenced both Ecorr and j from CP, resulting in deviations from expected design values. Keywords: Al alloy; CP analysis; electrochemical calculations; modeling investigations; Sw.

This review overviews recent advancements in studying corrosion scales formed on CS and low alloy steel surfaces in CO2/H2S environments. It discusses the chemical reactions, kinetics, mechanisms, classifications, influential factors, formation rates, types, and inhibitive properties of corrosion product scales that develop on steel surfaces. It thoroughly investigates phase transitions, the nature and composition of corrosion product scales, and their impact on the corrosion process by influencing the kinetics of anodic reaction (metal dissolution) and/or cathodic reaction (oxygen reduction/HER), which protect the corroding steel surfaces. Lastly, it emphasizes crucial research areas, knowledge gaps, future perspectives, and approaches for scale mitigation. Keywords: CO2/H2S corrosion; steel corrosion, corrosion mechanisms; corrosion scales; FeCO3; FeS.

MS is a very versatile and useful alloy in metal industry, since it is available and affordable, but it is prone to corrosion. This study investigated MS corrosion inhibition by modifying Zn₃(PO₄)2 bath with MgO and, then, with combined MgO and CaO additives. Different phosphating times (40, 60 and 80 min) and T (65 and 80 °C) were considered. Ct from 0 to 1.8 g/L MgO and combined MgO/CaO additives were added to Zn₃(PO₄)2 bath. SEM analysis of the coated samples was carried out. The specimens were also immersed in 3.5 wt% NaCl, for WL testing. Obtained results showed that the highest IE(%) of 56% was obtained for the MS sample at a phosphating T of 65 °C and Ct of 1.8 g/L MgO additive. For combined MgO and CaO additive, an IE(%) of 32% was obtained, at 65 °C, with a Ct of 0.9 g/L. MgO and CaO adsorption process (separately and combined) onto MS followed Freundlich’s adsorption model. ΔG indicated a physical adsorption process, and ΔH indicated an exothermic adsorption process, while ΔS during coating revealed a decrease in the process randomness degree. Keywords: Ca additive; corrosion; Mg additive; MS; Zn phosphating.

This study investigated a method for sustainable energy production which involved extracting lignin from waste Bm (AS, BTB, NTB and WnS), to use it as an energy source. The main goal was to advance alternative resources for producing transportation fuels and commodity chemicals, paving the way for a carbon-emission-free future. A pretreatment procedure was conducted, using methods such as EDX, SEM, TGA, proximate and ultimate analyses, to examine extracted lignin. Herein, WnS displayed the highest Bm-derived lignin Ct. BTB and NTB exhibited highest Ct from S, while, remarkably, AS showed the lowest one. NTB extraction process investigation revealed that minimum and maximum yields, at 2 and 3 h, produced lignin Ct of 6 and 8%, respectively. Similarly, BTB yielded 12 and 13% lignin, after 1 and 2 h, respectively. The study indicated that WnS possessed the highest lignin Ct. Furthermore, it was seen that varying certain parameters increased lignin yield. Keywords: biofuel; Bm; chemical treatment; green energy; lignin cellulose; production; renewable energy.

Herein, accurate voltammetric techniques were used for investigating Aza compound at an Au electrode in an aqueous universal BRB solution with pH 4.0 and at room temperature. Employed voltammetric methods were CV, ConvV and DeconvV, at various SR in the range from 40 to 800 mV/s. DSM was used to confirm experimental electrochemical parameters, and to identify the nature of the electrode reaction mechanistic pathway. Recorded CV revealed an uni-directional irreversible sharp anodic peak (Ep = 0.541 mV) in a BRB with pH 4.0. It indicated that the oxidation process was moderately fast. Electrons consumed in the electrode reaction were two. ConvV and DeconvV supported the presence of a chemical step coupled with electron transfer, due to the absence of the cathodic peak coupled in the reverse scan. Oxidative peak sharpness indicated some Aza adsorption control at the Au electrode surface. Keywords: Aza; DSM; electrochemical parameters; electrode reaction; voltammetric techniques.

Electrochemical and AA study of a new heterocyclic Schiff base (L1) was herein carried out for the first time. Electrochemical results and AA tests were performed using PDP, in vitro, by ABTS, C40H56/C18H32O2, DPPH and FRAP, respectively. IE(%) of this compound against corrosion of MS, immersed in a KOH simulated concrete solution (pH of 13.5), with 0.8 M Cl-, was investigated. Electrochemical results showed that L1 was a good CI, even at low Ct (from 10-3 to 10-6 M; τinhib > 98%), the best scavenger in DPPH and ABTS (IC50: 0.022 ± 0.00 and 0.003 ± 7.92E-05 μg/mL, respectively), and the most active in C40H56/C18H32O2 test, with a an IE(%) of 80.22 ± 1.58%. L1 exhibited a significant reducing capacity (A0.5: 0.008 ± 0.00 mg/mL) analogous to that obtained for Trolox (A0.5: 0.008 ± 9.14 05 mg/mL). This study demonstrated L1 good IE(%) and AA. Keywords: ABTS; AA; CI; DPPH; IE(%); L1

Abstract YSZ is a compound with an important role in electrochemistry applications, due to its high electrical conductivity. It is commonly used as electrolyte in solid-oxide fuel cells. Several studies have also suggested additional uses of this material as a proton conductor, when grown in Nc form. The present research reports combined theoretical and experimental results that examined the incorporation and properties of proton defect in YSZ. The calculations were based on DFT and NEB methods. MSS was also performed by studying muons evolution, a lighter hydrogen particle with non-zero spin. The results provided vital information on the formation energetics of proton defect, its migration behavior and electronic structure. Keywords: DFT; MSS; NEB; YSZ.

In Memoriam

This work focused on developing prediction models using ANN, in order to forecast the long-term performance of reinforcements in concrete slabs containing pure Mg anodes, and subjected to Cl- ingress. The experimental set-up consisted of two built RCC slabs with 1000 x 1000 x 100 mm. Slab #1 was cast with 3.5% NaCl by cement weight. Slab #2 was cast without NaCl. Considered input parameters were the distance of the anode from the point under consideration in x and y-axes, T, RH and concrete age in days. HCP values concerning SCE were considered output. Experimental values consisted of 80 HCP per slab/day. These were collected for 270 days, in order to generate the prediction model. The learning heuristic used LM supervised learning in feed-forward. A two-layer feed-forward network, with ten hidden sigmoid neurons and trained linear output neurons, was employed. The network architecture [5-10-1] and ten neurons in the hidden layer were used for all prediction models. The accuracy level of results obtained with LM was above 97%. Keywords: ANN model; Cl-induced corrosion; HCP; SA from Mg.

Patients with fractures require internal fixations, since treatment options are limited to metallic implants and autologous bone grafts. These limitations include chances of infection transference, quantity restrictions and the need for additional surgery. Bone tissue engineering seeks to address these limitations through the development of biocompatible bone scaffolds. This study fabricated a PLA based scaffold that sought to address some of the challenges associated with currently available treatment options. The methodology involved acquiring raw eggshells, which were rinsed with water and calcined with concentrated H3PO4. Hitherto, HAp powder was extracted from eggshells, and its presence was confirmed using color test. PLA (60,000 molecular weight) was procured from Sigma Aldrich, which was used with HAp powder, to form the composite, employing sol gel technique. SEM morphology established PLA, which has polymeric binding properties, as the 3D scaffold with the highest Ct (PLA/HAp (45/55 wt.%). It had a more consistent crystal and pore formation and weaker grain boundaries. FTIR analysis showed PLA characterizing peaks, and that functional groups present in 3D scaffold are not toxic to the body. X-RD spectra confirmed PLA and HAp presence in 3D scaffolds. However, peaks intensities decreased with lower Ct of HAp, and those of PLA increased in the 3D scaffold. This indicates that PLA and HAp particles have semi-crystalline and crystalline structures, respectively. Thus, 3D scaffolds can be tailored for many biomedical applications. Keywords: bone fillers; characterizations; HAp; PLA; scaffold.

Different Ct of KBE from its leaves were used to study its effect on MS corrosion resistance. Electrochemical methods such as PDP, EIS and WL tests were herein used. Experimental results showed that, with higher Ct of KB, its IE(%)increased. The highest corrosion IE(%) of 98.41, at 1600 ppm KBE in a 0.5 M H2SO4 solution, was obtained. The inhibitor´s adsorption onto the MS surface was excellent, since it created a monolayer. KBE´s adsorption mechanism obeyed Langmuir’s isotherm. SEM analysis established the development of a protective layer on the MS surface. Keywords: CI; EIS; LPR; PDP; SEM; WL.

Stoichiometry and B of Cd(II)/Na-DDTC complex were herein determined by DPV, employing Lingane’s equation in a simple and extended form. Ionic strength was kept constant by using NaClO4 and KNO3 as SE. All measurements were performed at a constant T of 298±1 K. The approximation of all possible Lingane’s equations was established. According to obtained results, it was concluded that the equation should be used in its extended form. In KNO3 and in NaClO4, q was found to be 5 and 6, and  logarithms were found to be 21.20 and 24.47, respectively. Spectrophotometric study was also performed to determine stoichiometry and  of Cd(II)/Na-DDTC complex in the same SE. Data indicated that Na-DDTC should be combined with Cd in molar ratios of 1:5 (ML5) in KNO3, and of 1:6 (ML6) in NaClO4.  logarithms were calculated to be 22.26 and 23.94 in KNO3 and NaClO4, respectively. IE(%) of Na-DDTC as an ecofriendly CI for CS in 0.5 M H2SO4 medium was also investigated using WL measurements. Experimental results showed that IE(%) increased with higher inhibitor’s Ct. The inhibitor’s adsorption onto the CS surface obeyed Langmuir’s isotherm, and it proceeded by both physisorption and chemisorption modes. ΔGads was determined. The effect of Cd2+ addition, which formed a complex with Na-DDTC, was also studied. Keywords: B; CI; DPV; Job’s method; Na-DDTC.

In the present study, a thin film of NixSy was deposited on an ITO GP by SILAR method. This film was characterized by UV-vis reflectance and FTIR spectroscopy. UV-vis reflectance revealed that Eg from NixSy was 1.55 eV. After coating, ITO GP Eg decreased from 1.88 to 1.55 eV. This indicates that the film functioned as a semi conductor. UV-vis absorbance showed that the film absorbance occurred at 322.00, 388.80 and 396.25 nm, with peak intensity of 1.229, 0.934 and 0.916 AU, respectively. FTIR spectra confirmed NixSy formation on ITO GP by SILAR technique. Thus, it was encouraging to note that NixSy was successfully prepared by this method. Electrochemical studies, such as polarization technique and AC impedance spectra revealed that current flowing through ITO GP increased after NixSy coating by SILAR method. These findings may be useful for solar panel systems used in marine environments. Keywords: Eg; electrochemical studies; ITO GP; NixSy; SILAR method; thin film.

Bd was produced by transesterification of refined NSO with MeOH and CaO catalyst using batch mode. Physicochemical properties of NSO and Bd as an alternative diesel fuel were characterized using ASTM fuel test standards. The FA composition and functional groups of Bd were investigated using GC-MS and FT-IR, respectively. The effect of basic parameters such as reaction catalyst Ct, MeOH/oil molar ratio, reaction T and time, and SS were determined using batch mode. These process parameters were optimized using RSM and ANOVA. The importance of various process parameters and their combined effects on transesterification performance was determined through CCD. Statistical analyzes of the data led to the development of a second-order quadratic polynomial regression model that established the relationship between Bd yield and process variables. The model was able to adequately predict Bd yield with R2 value of 0.9942. The obtained results were in good agreement with published data for Bd from other vegetable oils, as well as with various international standards for this product. An optimal yield of 94% was achieved under optimal conditions of catalyst Ct (4 wt%), MeOH/oil molar ratio of 8:1, T of 55 °C, time of 60 min and SS of 400 rpm. The results show that Bd produced using alcohol in the transesterification process improved CP and CFPP properties. Keywords: ANOVA; Bd; NSO; oil transesterification; optimization; RSM.

Poultry meat is a high-protein source that is consumed all over the world. This source is tainted not only by viruses but also by environmental contaminants, including HM. This study aimed to detect HM in the tissues (liver, gizzard, muscles, heart and kidney) of BC and DC in Quetta city, Balochistan, Pakistan for the first time, using AAF. Samples were collected from different regions of the district, and prepared for analysis. The measured Ct (mg/L) of detected HM like Pb (0.30-0.83), Co (0.18-0.35), Mn (0.10-0.21), Fe (0.32-12.70) and Cu (3.79-4.51) varied across different organs in analyzed BC and DC samples. Cu, Mn, Co and Fe content was within the range of acceptable values established by WHO and ANZFA. However, Ct of Pb for BC and DC exceeded WHO’s (0.2 mg/L) and EU’s (0.1 mg/L) permissible limits. Therefore, more in depth research studies on poultry feed should be carried out, for its improvement and safety. Keywords: AAS; BC; DC; HM.

NH has the ability to control corrosion of various metals and alloys such as Al, CS, Cu, Cu Sn, MS, Sn and SS. It behaves as a CI in acidic, basic or neutral media. In the several studies herein reviewed, various techniques like WL, and electrochemical methods such as PDP and EIS, have been used to evaluate NH corrosion IE (%). Protective films have been analyzed by FT-IR, UV-vis spectroscopy, GC-MS, SEM and EDX methods. NH adsorption onto the metals and alloys surface has obeyed Langmuir’s isotherm. PDP studies have revealed that NH may function as an anodic, cathodic or mixed type of CI, depending on the metal nature and on the corrosive environment. Keywords: CI; EDX; EIS; FT-IR; GC-MS; NH; PDP; SEM; WL.

Modern predictive modeling techniques, such as regression, NN and decision trees can be used to build better and more useful models. JMP 17.2.0 was used in this study to develop a fitting model for microbial growth observed data from chicken manure and banana peels labelled as Sample A, and a single chicken manure substrate, identified as Sample B. Statistical metrics, including COD (R2), RASE, MAD, negative log-likelihood and SSE were used to determine best predictions for Ct (X) from biomass of 22 and 24 samples (A and B) on SC (S) and SGR of microorganisms (μ). Along with estimated Monod parameters, TanH function SAS codes for 3 declared hidden layers, also demonstrated by surface plots, portrayed Sample B predicted model as the best one, even though the 2 samples datasets R2 values for training (A: 0.9887916 and B: 1.0000) and validation (A: 0.9787637 and B: 0.9999999) pointed to a good fit. According to findings, optimal conditions for datasets were: A- biomass = 899868717 mg/L and SC = 4.62 x 109 mg/L, correspondent to high µ (0.010201 h-1); and B- biomass = 15351147 mg/L and SC = 9.2322 x 109 mg/L, consistent with µ of 0.007316 h-1. RMSE, which is the standard method of choice for evaluating the accuracy of predictive models, including those based on NN, should be activated in future studies. This research is both timely and relevant in the pursuit of sustainable waste management and renewable energy generation. Keywords: ANN; JMP; Monod; SAS code; SGR; SC; TanH function.