The anodic hydrogen evolution (AHE) on Mg, MgZn
2
(η-phase), Al
4
Cu
2
Mg
8
Si
7
(Q-phase), and Mg
2
Si (β-phase) intermetallic compounds has been investigated using hydrogen evolution technique and ...customized polarization schemes. Results show that at constant applied anodic current densities, the hydrogen evolution rates on pure Mg and MgZn
2
are much higher than those of Q-phase and Mg
2
Si, indicating AHE is not very pronounced on Q-phase and Mg
2
Si. After anodic galvanostatic polarization, an obvious enhanced cathodic activity was observed for Mg, MgZn
2
, and Al
4
Cu
2
Mg
8
Si
7
with no obvious change for Mg
2
Si. The stepped galvanostatic-potentiostatic tests reveal that pure Mg has the highest degree of cathodic activity enhancement with the increase of applied anodic current density, followed by Q-phase and MgZn
2
, while no obvious change of cathodic activity was noted in the case of Mg
2
Si. No single model was seen to be suitable for explaining the observed AHE of all the electrodes at the same time. However, the “incomplete film univalent Mg
+
ion mechanism” and the “enhanced catalytic activity mechanism” can explain the observed experimental phenomena in many cases.
The stability of corrosion films on the Q-phase (Al5Cu2Mg8Si6) under different pH environments ranging from pH 1 to pH 13 in 0.1 M NaCl solution has been investigated using Atomic Force Microscopy ...(AFM) and Electrochemical impedance spectroscopy (EIS). The magnitude of Rct and Rf of Q-phase was noted to vary with pH. At pH 4 and 6, the values of Rct and Rf were higher by about 3 orders of magnitude than the values at pH 1 and 13. This indicates better protection of the metal towards corrosion under neutral conditions. The polarization resistance (Rct + Rf) obtained from the fitting parameter is observed to follow the order pH 6 > pH 4 > pH 10 >> pH2 > pH12 > pH13 > pH 1. The EIS response showed a capacitive behavior. From surface topography and cross section topography characterization there were significant differences in the surface characteristics of Q-phase under different pH values. The microscopic topographic analysis suggests copious accumulation of corrosion products in near neutral environments and the lowest surface roughness was observed in the alkaline environment. Quantitative surface roughness characterization shows that a maximum surface roughness was at pH 2 which decreases with increased basicity of the environment. Results indicate that the corrosion film stability decreases with increased deviation from the neutral pH environment.
The pH effect on the surface and interfacial films on η-phase (MgZn2) in aqueous solutions under acidic, neutral, and alkaline conditions has been evaluated using time of flight-secondary ion ...spectroscopy (TOF-SIMS), Atomic force microscopy (AFM) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX). TOF-SIMS depth profile plots reveal that under an acidic environment (pH2) deep corrosion penetration occurs with a dispersion of corrosion products which claims a considerable depth matrix cross-section. Under near neutral environments (pH 6), the corrosion film is seen to be stratified into two layers of different compositions, while in a slightly alkaline environment (pH 10) the film appears not to be distinctly differentiated, whereas in a very alkaline environment (pH 13) a compact film rich in hydroxides develops. TOF-SIMs surface and depth profile maps were consistent with the depth profile plots. SEM and AFM images reveal that the surface roughness increased in with a decrease in pH value from the acidic to the alkaline environments. EDX elemental composition analysis also indicated a severe drop in the zinc content of the film in the alkaline environment. Largely, metallic zinc enrichment occurs following the initial magnesium dissolution whose stability is greatly affected by the near-surface pH of the bulk solution, thus, giving rise to different film structures.
The influence of variations in pH and time on the bimetallic corrosion of π-Al8Mg3FeSi6 phase and pure aluminum in acidic, neutral and basic solutions has been evaluated by potentiodynamic ...polarization and scanning vibrating electrode technique (SVET) in combination with Energy dispersive X-ray spectroscopy (EDX). The bimetallic corrosion of π-Al8Mg3FeSi6/Al couple was found to depend on time and pH. Polarization tests show that at pH 2 (acidic) and pH 6 (near-neutral), the π- phase functions as the anode while Al functioned as the cathode, whereas the opposite was observed at pH 13 (basic). SVET scans show that in pH 2 and 13 solutions, cathodic fluxes emerge from π- phase, and the anodic fluxes develop from Al. Whereas in pH 6 solution, self-dissolution of π- phase occurs and both cathodic anodic processes develop on the π- phase with no conspicuous electrochemical activity on Al. The rigor of the bimetallic coupling of π- phase and Al was more pronounced at pH 2 and 13 and the order of the intensity of the galvanic effect is pH 13 > pH 2 > pH 6. EDX surface analysis indicates preferential discharge of more electropositive elements in π-Al8Mg3FeSi6 phase in solution. In acidic and neutral environments selective dissolution of Mg/Al in π- phase the occurs, in near neutral solutions selective dissolution of Mg occurs, in alkaline environments selective dissolution of Al occurs; these lead to the enrichment of more noble elements which have a direct impact on the galvanic polarity of the π-Al8Mg3FeSi6 in the long term.
Purpose
This paper aims to appraise the inhibitory effect of saponins extracted from Gongronema latifolium (SEGL) on mild steel in acid media. This is in a bid to conserve our environment and ...maintain the integrity of engineering structures and materials.
Design/methodology/approach
The corrosion inhibition of SEGL and ethanolic extracts of the leaves of G. latifolium (EEGL) on mild steel was studied by hydrogen evolution technique within a temperature range of 30-60°C in tetraoxosulphate (VI) acid solutions.
Findings
The extracts inhibit the corrosion of mild steel, and the inhibition efficiency depends on the concentration of the plant extract, temperature and the period of immersion. SEGL was comparatively more efficient than EEGL. Optimum values of the inhibition efficiency for both the EEGL and SEGL (93.7 and 96.5 per cent, respectively) were obtained at extract concentration of 10 g/L, whereas the least values were obtained at extract concentration of 0.5 g/L.
Originality/value
This paper provides new information on the possible application of isolated SEGL as an environmentally friendly corrosion inhibitor. The possible mechanism of the inhibitive action is also given.
The corrosion behavior of C20 pipeline steel was studied under Fe oxide and sand deposits in oilfield produced water containing sulfate‐reducing bacteria (SRB) via electrochemical techniques and ...surface analyses. A galvanic current of about 2 μAcm−2 was detected when the Fe oxide deposited sample and the bare steel were coupled in zero resistance ammeter (ZRA) mode, with the former being the anodic member of the couple. The Fe oxide deposited steel recorded severe localized corrosion after 14 days of testing in the SRB inoculated oilfield produced water. Corrosion severity decreased on the sand‐deposited steel, with general corrosion as the dominant morphology of surface attack. The development of product film was a vital factor in steel corrosion under the Fe oxide deposit.
The corrosion behavior of C20 pipeline steel was studied under Fe oxide and sand deposits in oilfield‐produced water containing sulfate‐reducing bacteria (SRB). The Fe oxide deposited steel suffered severe localized corrosion after 14 days of testing, while corrosion severity decreased on the sand‐deposited steel, with general corrosion as the dominant morphology of surface attack.
The rising costs of lithium and other versatile metals which are of electrochemical importance have sprouted concerns in the electrochemical world. Sodium and sodium-ion batteries have been found to ...re-emerged as a candidate for medium- and large-scale stationary energy storages. This is due to the elevated involvement in renewable energy sources that provide intermittent power which needs to be load leveled. In view of this reality, the electronic structure investigations and the electrochemical mechanistic performances of Al
12
N
12
, Mg
12
O
12
, Ca
12
O
12
, and C
23
N nanocages as potential energy storage materials are reported herein based on density functional theory (DFT) calculations at the M06-2X/6–311 + G(d,p) level of theory. From electronic properties, Na@C
23
N was observed to have the higher energy gap of 4.06 eV, meanwhile Na@Mg
12
O
12
had the least energy gap of 2.60 eV, indicating higher stability and reactivity of the system compared to its counterpart. The higher electron density was observed from Na@Al
12
N
12
having 0.30 a.u. From the electrochemical studies, Na
+
@C
23
N had the higher Gibbs free energy (Δ
G
cell
) of − 159.63 kcal/mol which conformed with the reactivity index of the system. The higher
V
cell
value of 6.92 V was observed from Na
+
@C
23
N system. The mechanistic studies provided herein indicated that the modeled systems specifically Na
+
@C
23
N are promising anode material for sodium-ion battery application.
Prostate cancer that is resistant to castration has been a prominent health challenge in the lives of men, particularly older men. This study looks at the spectroscopic properties, density functional ...theory (DFT) calculations, and molecular docking of the chemical N-(1H-pyrrol-2-yl) methylene)-4-methylaniline(PMMA) in order to see if it can be used as a chemotherapeutic medication for the treatment of castration-resistant prostate cancer(CRPC). The frontier molecular orbitals (FMO), Fukui reactivity functions, non-linear optics (NLO), and natural bond orbitals (NBO) were investigated further using DFT at the 6–311++G (d, p) with five different functional (B3LYP, B3PW91, ɷB97XD, PBEPBE, and M06–2X) for the investigation of the studied molecular structural properties. The experimental and theoretical vibration analysis of the synthesized molecule employing DFT investigations in different solvents at B3PW91/6–311++G (d, p) were found to be in good agreement. The docking results with three different proteins (4XVE, 1XF0, 5Y8Y) with PMMA showed good binding affinities when compared to the standard drug (Darolutamide) (DLA). The molecular docking results indicated that PMMA have an excellent chemotherapeutic potential for the treatment of CRPC.
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The electrochemical behavior of a bulk-synthesized MgZn
2
intermetallic compound in aerated 0.1 M NaCl solutions has been studied as a function of pH and applied potential using polarization ...techniques, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and focused ion beam-transmission electron microscopy (FIB-TEM). The anodic activity of MgZn
2
is seen to decrease with an increase in pH value. Polarization tests reveal two limiting current densities in pH 4 solution at relatively high and low potentials. At pH 12, passivity is observed with a lower limiting current density compared to those observed at pH 4. The corrosion film formed after potentiostatic polarization in the pH 4 solution is composed of a bilayer at a less negative potential and a single layer at a more negative potential. In the case of pH 12 solution, a protective compact bilayer film is formed irrespective of the potential within the passive zone. Overall, the corrosion mechanism of MgZn
2
is by early dissolution of Mg leading to a Zn-enriched surface whose subsequent dissolution depends on the value of the applied potential.
The durability and functionality of many metallic structures are seriously threatened by corrosion, which makes the development of anticorrosive coatings imperative. This state-of-the-art survey ...explores the recent developments in the field of anticorrosive organic coatings modulated by innovations involving nano/microcontainers with porous matrices. The integration of these cutting-edge delivery systems seeks to improve the protective properties of coatings by enabling controlled release, extended durability, targeted application of corrosion inhibitors, and can be co-constructed to achieve defect filling by polymeric materials. The major highlight of this review is an in-depth analysis of the functionalities provided by porous nano/microcontainers in the active protection and self-healing of anticorrosive coatings, including their performance evaluation. In one case, after 20 days of immersion in 0.1 M NaCl, a scratched coating containing mesoporous silica nanoparticles loaded with an inhibitor benzotriazole and shelled with polydopamine (MSNs-BTA@PDA) exhibited coating restoration indicated by a sustained corrosion resistance rise over an extended period monitored by impedance values at 0.01 Hz frequency, rising from 8.3 × 104 to 7.0 × 105 Ω cm2, a trend assigned to active protection by the release of inhibitors and self-healing capabilities. Additionally, some functions related to anti-fouling and heat preservation by nano/microcontainers are highlighted. Based on the literature survey, some desirable properties, current challenges, and prospects of anticorrosive coatings doped with nano/microcontainers have been summarized. The knowledge gained from this survey will shape future research directions and applications in a variety of industrial areas, in addition to advancing smart corrosion prevention technology.
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•Types and fabrication techniques of porous nano/microcontainers are summarized.•Anticorrosion, self-healing, anti-fouling and heat preservation are among the functionalities provided by nano/microcontainers in coatings.•Recent developments and evaluation techniques in smart anticorrosive coating are reviewed.•A summary of desirable properties and challenges of organic coating is presented.
