Potentiodynamic Polarization Curves

Magnesium is potentially useful for orthopaedic and cardiovascular applications. However, the corrosion rate of this metal is so high that its degradation occurs before the end of the healing process. In industrial media the behaviour of several magnesium alloys have been probed to be better than magnesium performance. However, the information related to their corrosion behaviour in biological media is insufficient. The aim of this work is to study the influence of the components of organic fluids on the corrosion behaviour of Mg and AZ31 and LAE442 alloys using potentiodynamic, potentiostatic and EIS techniques. Results showed localized attack in chloride containing media. The breakdown potential decreased when chloride concentration increased. The potential range of the passivation region was extended in the presence of albumin. EIS measurements showed that the corrosion behaviour of the AZ31 was very different from that of LAE442 alloy in chloride solutions.

The electrodeposition process plays a crucial role in the formation of thin films on materials, in particular, the electrodeposition of nickel-phosphorus because of its important properties. In this study, Ni-P coatings were deposited on X52 steel substrates by electrodeposition technique from a solution containing nickel sulfate, sodium hypophosphite (NaH2PO2). Composition, surface morphology, and mechanical properties of the Ni-P deposits were studied using SEM, EDAX, the Vickers method, weight loss and potentiodynamic polarization techniques. The effects of the current density were investigated on the surface morphology, phosphorus content, microhardness and corrosion of the coatings. It was observed that both the phosphorus content and microhardness are dependent on the current density. Results demonstrate that the morphology of the electrodeposited Ni-P alloys shows that the grains are spherical in nature for all the samples. It has been observed that the influence of current density on the P content of the deposit is an inverse relation with phosphorous content and also the as-plated coatings at current density of 5 Am -4 exhibit the superior microhardness. Corrosion tests show that 5 Am -4 is the best current density value which gives the best protection coating against corrosion.

Tin and tin–alloy deposits enjoy many applications in the electronics, tribology and engineering industries with potential applications as electrodes for lithium batteries and as electrocatalyst coatings. Methanesulphonic acid (MSA) has become a favoured electrolyte due to its environmental benefits and ability to offer a vehicle for many metal alloy, conductive polymer and composite coatings. A number of emergent uses require less common compositions or structures of alloy, polymer or composite deposits. This paper concisely provides diverse examples of modern tin-containing deposits from aqueous MSA, including Sn–Cu alloys having a very wide composition together with a wide range of colours (golden-yellow–dark-brown) and surface finishes, a Sn–Cu composite deposit containing ceramic, protonated titanium oxide nanotubes for batteries, a tin–copper–bismuth ternary alloy and tin deposits supported on an inert reticulated vitreous carbon or carbon felt substrate to provide a porous, t...

Corrosion is a significant issue across various industries, leading to substantial economic losses and environmental concerns. The limitations of conventional corrosion inhibitors, often associated with toxicity and environmental hazards, have sparked interest in sustainable alternatives. Essential oils (EOs) have gained attention as green corrosion inhibitors due to their natural origin, biodegradability, and low environmental impact. This review explores the potential of EOs for corrosion protection, focusing on their chemical composition, mechanisms of action, and experimental and computational methods used to evaluate their effectiveness. EOs are complex mixtures of bioactive compounds, including terpenoids, phenolics, and flavonoids, which interact with metal surfaces to form protective films, inhibiting electron transfer and reducing corrosion rates. These interactions are influenced by factors such as concentration, temperature, metal type, and the corrosive environment. Experimental techniques such as weight loss measurements, electrochemical impedance spectroscopy (EIS), and surface analysis methods demonstrate the high efficiency of EOs, with inhibition efficiencies often exceeding 90%. Computational approaches, including quantum chemical calculations and molecular dynamics simulations, complement experimental findings, offering insights into adsorption mechanisms and molecular stability. While EOs present numerous advantages, including sustainability and low toxicity, challenges remain, such as variability in composition, cost, and scalability. This review highlights the potential of EOs as eco-friendly corrosion inhibitors, advocating for further research to optimize their application and overcome current limitations, paving the way for sustainable corrosion protection strategies.

Novel surfactants were synthesized based on cottonseed oil and diethanolamine and the structures of these compounds were confirmed by FTIR spectroscopy. The surface and thermodynamic properties of these compounds have been investigated. The corrosion behavior of the synthesized surfactant corrosion inhibitors was evaluated by using potentiodynamic (Tafel) polarization curves, linear polarization resistance corrosion rate techniques. The experimental results showed that these inhibitors revealed a very good corrosion inhibition even at low concentrations. The protection efficiency increased with increasing inhibitor concentration, getting maximum values ranged between 87.37 and 97.91 % at 100 ppm after 20 hour of exposure. The adsorption process was found to obey the Langmuir adsorption isotherm.

The inhibition effect of eugenol oil (EO) on the corrosion of tin in 0.1 M Na2CO3 has been studied by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization technics. The effect of temperature on the corrosion behavior of tin in 0.1 M Na2CO3 with and without addition of eugenol oil was studied in the temperature range 278-308 K. This compound inhibits the corrosion of tin at low concentration. At 4g/L eugenol oil the inhibition efficiency calculated by potentiodynamic polarization and EIS techniques is 70% and 82%, respectively. The inhibition efficiency increased with increase of the inhibitor concentration and decreased with increase of medium temperature. Electrochemical impedance spectroscopy was used to investigate the mechanism of corrosion inhibition. Polarization curves reveal that EO acts as a mixed-type inhibitor in corrosive solution. The results obtained from the different corrosion evaluation techniques are in good agreement.

This study explores the effectiveness of geranium essential oil (GEO) as an environmentally sustainable corrosion inhibitor for XC48 carbon steel in a 1 M HCl solution. The chemical composition of GEO, characterized by GC/FID, identified geraniol (19.53%) and β-citronellol (17.25%) as the main components. Electrochemical analyses, including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS), indicated that GEO functions as a mixed-type inhibitor, achieving a maximum inhibition efficiency of 89.82% at a concentration of 2.0 g/L. Gravimetric analysis further showed a significant decrease in corrosion rate with increasing GEO concentration, though inhibition efficiency declined at elevated temperatures (298-328 K), likely due to the desorption of inhibitor molecules from the steel surface. Activation energy (E a) values increased with GEO concentration, suggesting the formation of a physical adsorption layer that hinders corrosion. Positive activation enthalpy (ΔH*) values confirmed the endothermic nature of the steel dissolution process, while increased entropy (ΔS*) with GEO concentration pointed to enhanced system disorder due to water displacement on the surface. Computational modeling provided additional insights, with quantum chemical calculations pointing to (E)-citral and citronellyl tiglate as particularly reactive constituents based on favorable electronic properties. Monte Carlo simulations corroborated these findings by highlighting strong interactions between specific GEO molecules, such as β-citronellol and α-costol, and the steel surface. The results confirm that GEO offers a promising eco-friendly alternative to conventional corrosion inhibitors.

Oligosuccinimide (OSI) is an oligomer with several repeating units of succinimide. In this study, OSI was synthesized by thermal condensation between maleic anhydride and ammonium carbonate. The chemical structure of the synthesized compound was confirmed by FTIR and NMR spectroscopy as well as LC-MS characterization. Evaluation of its performance as corrosion inhibitor and the adsorption mechanism on a carbon steel surface in CO2saturated 1% (w/v) NaCl solution was performed using electrochemical techniques (electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization) and weight-loss methods. These tests were simultaneously carried out for all fractions without separation. The EIS results showed that the inhibition efficiency (IE) of the OSI increased with increasing concentration but decreased at higher temperatures. The potentiodynamic polarization data indicated that the OSI acted as a mixed inhibitor. Adsorption of OSI on the carbon steel generally obeys the Langmuir adsorption isotherm according to curve linearity, which relates the degree of surface coverage to the inhibitor concentration. The standard Gibbs free energy of the adsorption values (∆𝐺 𝑎𝑑𝑠 𝑜 ) were negative within the range of -33.14 to -38.73 kJ.mol -1 , which indicates the spontaneity of the adsorption process on the carbon steel surface and that OSI molecules interacted with the carbon steel through semi-physisorption.

The objective of this study is to investigate and predict the effectiveness of the Blue Tansy
essential oil (BTES) as a corrosion inhibitor. The chemical composition of BTES was
determined using gas chromatography (GC) coupled with a flame ionization detector (FID). To
evaluate the corrosion resistance of mild steel in a 1 M hydrochloric acid solution, weight loss
measurements, potentiodynamic polarization, and dynamic electrochemical impedance
spectroscopy (EIS) were conducted. The inhibition efficiency of BTES showed an increasing
trend with higher inhibitor concentrations, and its inhibitory behavior exhibited damped
oscillations. The results obtained from the various electrochemical measurements were
consistent, with the maximum inhibition efficiency of 60% observed at a BTES concentration
of 2 g/l. Through the analysis of the polarization curves, it can be inferred that the BTES acts as
a mixed-type inhibitor. To enhance the experimental findings, computational investigations
were conducted to gain insights into the molecular-level interactions between the BTES
molecules and the metal surface. These calculations utilized the Density Functional Tight
Binding (DFTB+) theory. In order to predict the effectiveness of the BTES as a corrosion
inhibitor, Monte Carlo simulations were employed. This simulation approach considered all the
constituent molecules of the BTES in both gas and aqueous phases, allowing for a
comprehensive understanding of its anti-corrosion mechanism.

Sustainable materials encompass a diverse range of substances used in both consumer
and industrial domains. These materials are sourced in quantities that safeguard non-renewable
resources and environmental equilibrium, with a focus on bio-based alternatives derived from plants.
This study investigates the corrosion inhibition potential of two distinct Blue Tansy essential oils
(BTES 1 and BTES 2) with varying chemical compositions. Corrosion resistance for mild steel in 1 M
HCl environment was assessed using weight loss and Potentiodynamic polarization techniques. The
evaluation of BTES 1 and BTES 2 revealed compelling insights. Notably, their inhibition efficiency
exhibited an intriguing, damped oscillation pattern with fluctuating concentrations. Remarkably, at
0.5 g/L concentration, BTES 1 achieved an impressive 80% inhibition, while BTES 2 demonstrated a
substantial 70% inhibition at 2.5 g/L. This behavior stems from intricate interactions among active
compounds, leading to protective film formation and competitive adsorption effects. Importantly,
congruence between weight loss measurements and potentiodynamic polarization curves fortified
the reliability of outcomes. The study also confirmed BTES as a mixed-type inhibitor, as indicated by
polarization curves. Furthermore, Petra/Osiris/Molinspiration (POM) analyses were conducted to
unravel molecule interactions, elucidate toxicity risks, and assess bioactivity scores. This comprehensive exploration sheds light on the interplay between sustainable materials, corrosion inhibition
efficacy, and complex molecular dynamics, enhancing our understanding of environmentally conscious corrosion prevention strategie

This article focuses on optimising the submerged arc welding process to improve the microstructural and mechanical characteristics of welded S690QL steel joints efficiently without preheating, using a Taguchi optimisation approach. Trail runs were performed initially for bead-on-plate studies to optimise the weld cycle ranges by investigating weld characteristics such as microstructural morphology and toughness in the weld zone. Selected weld cycle ranges from bead-on-plate studies were further analysed and optimised through butt weld investigations. The phase transformations in microstructure at the weld and heat-affected zone from tempered martensite, martensite, and bainite to dendritic ferrite, lath bainite, and lath martensitic phase were observed with a change in heat input from 0.91 kJ/mm to 1.37 kJ/mm. The weld residual stresses were tensile at the weld and compressive away from the weld zone, diminishing gradually with an increase in transverse distance from the weld. The overall weld efficiency, weld residual stress concentration and mechanical characteristics of the welded butt joint were improved at a controlled heat input of 1.19 kJ/mm. An increase in heat input beyond the optimised limits influences the extent of the heat-affected zone and the joint’s toughness due to the coarsening of the weld microstructure towards the fusion boundary.

Titanium and its alloys are widely used owing to their high strength-to-weight ratio, good tensile strength, and resistance to corrosion. The Ti6Al4V alloy is called the workhorse among the titanium alloys owing to its wide application. Even though the Ti6Al4V alloy is immune to corrosion, improper welding conditions lead to contamination, making the weldments prone to stress corrosion cracking (SCC). These weldments are susceptible to SCC if they show sensitivity to pitting. This study examines the effect of welding conditions on the pitting corrosion behavior of 3 mm thick plates of Ti6Al4V alloy. The Ti6Al4V weldments were fabricated using fusion welding methods, namely, the gas tungsten arc welding (GTAW) and laser beam welding (LBW) techniques. The pitting corrosion studies were carried out by a potentiodynamic polarization technique, using non-deaerated 3.5% NaCl solution of pH 7, to create a marine corrosion environment. The pitting corrosion studies yielded good results as there was corrosion resistance in weldments fabricated under controlled conditions.

The waterborne soya alkyd (WSA) and its RGO dispersed nanocomposites (WSA-RGO) were synthesized via ex-situ polymerization using solvent-less green approach. The soya oil monoglyceride was used as precursor for waterborne alkyd. The synergistic effect of nanofillers and poly melamine co-formaldehyde isobutylated solution modified organic matrix (WSA) on physico-mechanical and corrosion inhibition of these coatings on finally polished carbon steel (CS) was investigated. Their physico-chemical, physico-mechanical and thermal properties were analyzed using standard protocols. The electrochemical corrosion measurements of these coatings were performed using Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy. The aforementioned studies revealed that the nanocomposite coatings exhibit promising corrosion protection performance which is evident from the i corr , E corr , impedance and phase angle values of coatings (i.e. i corr 7.736×10-9 Acm-2 , E corr-0.191 V, impedance ~10 7 Ω cm 2 and phase angle 86 o). These results suggest that the proposed waterborne nanocomposite coatings exhibit superior corrosion protection property than those of other such earlier reported systems.

The effect of heat treatment of nickel-aluminum bronze alloy on the interaction of the cathodic surface and its corrosion behavior in 3.5% NaCl solution is studied. The alloy was studied under different industrially recommended heat treatments, including quenching, normalizing and aging heat treatments. The microstructure of the specimens was studied by optical microscopy. Polarization tests proved that with increasing immersion time, and the formation of the protective layer, helps extend the oxygen-diffusion controlled cathodic reactions and also increase corrosion resistance. Polarization curves showed that the anodic polarization behavior is almost the same for all samples, which suggests that activation is controlled by the heat treatment of the samples. The different behavior under the influence of cathodic polarization proves that the alloy also reflects the increase or decrease in the level of corrosion resistance.

In this study, four Cr-Mn austenitic steels (Ni-free) were fabricated by vacuum induction melting. Several
plates with 10 mm thickness were produced by hot-rolling. Corrosion behaviour of Cr-Mn austenitic
steels and 316L stainless steel in 0.1 M H2SO4 solution was investigated using open-circuit potential,
potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) test techniques. The
results indicated that the open-circuit potentials of four Cr-Mn austenitic steels are shifted towards
positive values. In addition, the potentiodynamic polarization curves suggested that four Cr-Mn austenitic
steels represent comparable passive behaviour within the 0.1 M H2SO4 solution. Nyquist plots for the Cr-
Mn steels in 0.1 M H2SO4 solution also showed a capacitive loop at high and medium frequencies and an
inductive loop at low frequencies.

Recently, mixed-metal oxides with suitable properties such as high chemical resistance and thermal
stability, have been used in a wide range of applications as corrosion resistant coatings. In the present
study, Aluminum/Magnesium/Titanium mixed-metal oxides was used as a coating on AA1100 aluminum
by sol-gel method and by dip coating process and the effect of various molar fractions and heat treatment
cycle on properties of this coating was investigated. In order to study the effect of crystallinity of the
coated samples, test samples were characterized using X-ray diffraction (XRD) and Vickers
microhardness analyses and their microstructures were examined by Scanning Electron Microscope
(SEM). The corrosion behavior of samples were also studied by Open Circuit Potential (OCP) and
potentiodynamic polarization techniques in 3.5 wt.% NaCl solution. The results showed that the
amorphous sol-gel coatings are less porous representing better corrosion resistance when they are
compared with the crystalline coatings. The corrosion rates of the crystalline samples with Al/Mg/Ti
molar ratios of 5:1:3 and 2.5:3:4 were 5 and 13 times greater, respectively, than those for the amorphous
samples and the porosity contents in the former samples with the same molar ratios were 17 and 27 times
greater than those of the latter samples, respectively.

By utilizing weight loss measurements and electrochemical technique, the corrosion inhibition efficiency of Cucurbita maxima peel and seed extracts on Grade 304 austenitic stainless steel in 1 M sulphuric acid solution was examined. The efficacy of C. maxima extracts' inhibition increased with concentration while decreasing with temperature. At 0.7 g/L extract concentration for 3 hours of immersion, the inhibitor's greatest efficiency was 95.21% for PCM and 94.26% for SCM. Stainless steel corrosion was successfully inhibited by C. maxima peel and seed extracts, according to the results, and it was discovered that the presence of halide ions enhanced the efficacy of the inhibition. The synergistic effect of halide ions was found to follow the order: KI > KCl. According to the polarization curve, C. maxima functions as a mixed-type inhibitor. Due to the extract components' adsorption on the stainless steel surface, peel and seed extracts exhibit an inhibitory effect. The activation energy of the corrosion reaction increases by the presence of both extracts. The physical adsorption is shown by the negative values of ΔGads, which range from-12 kJ/mol to-18 kJ/mol. These values show the spontaneity of the adsorption process. Adsorption is a physical process that adheres to Langmuir adsorption isotherms. The results of a study using scanning electron microscopy to examine the surface morphology of stainless steel in inhibited and uninhibited acid solutions revealed that the presence of extract and halide inhibitors remarkably lowers the corrosion rate. This is as a result of the extract and halide inhibitor molecules adhering to the surface and forming a barrier that prevents an acid attack.

Plasma electrolytic oxidation (PEO) of 7075 Al alloy was carried out in silicate base electrolyte containing 200 nm diameter α-Al 2 O 3 particles for producing composite coatings. The process was performed under a softsparking regime using a pulsed bipolar signal with several concentrations of α-Al 2 O 3 particles. It was found that the incorporation of α-Al 2 O 3 particles into the coating did not significantly alter the thickness and roughness of the coating. However, the α-Al 2 O 3 particles were detected on surface of the composite coatings. Corrosion tests showed significant improvement in corrosion performance of the composite coatings due to the efficient pore blocking provided by α-Al 2 O 3 particles, which enhances the barrier performance of both inner and outer layers of the coatings. However, the long-term EIS measurements showed that the performance of composite coatings becomes close to that of particle-free coating after 56 days of immersion in chloride containing solution. Tribocorrosion tests showed that adding 3 g•l −1 of α-Al 2 O 3 particles to the electrolyte bath decreased the lost wear volume of the resulted coating from 30 to 10 mm 3 (×10 −3). Higher α-Al 2 O 3 particles concentration (i.e. 7 g•l −1) showed detrimental effect on both corrosion and tribocorrosion performance of the coating.

The inhibition effect of eugenol oil (EO) on the corrosion of tin in 0.1 M Na2CO3 has been studied by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization technics. The effect of temperature on the corrosion behavior of tin in 0.1 M Na2CO3 with and without addition of eugenol oil was studied in the temperature range 278-308 K. This compound inhibits the corrosion of tin at low concentration. At 4g/L eugenol oil the inhibition efficiency calculated by potentiodynamic polarization and EIS techniques is 70% and 82%, respectively. The inhibition efficiency increased with increase of the inhibitor concentration and decreased with increase of medium temperature. Electrochemical impedance spectroscopy was used to investigate the mechanism of corrosion inhibition. Polarization curves reveal that EO acts as a mixed-type inhibitor in corrosive solution. The results obtained from the different corrosion evaluation techniques are in good agreement.

RESUMEN El presente trabajo pretende hacer un aporte al conocimiento del comportamiento electroquimico de recipientes de hojalata en medio del ion citrato y al papel que juega la formacion de complejos metalicos solubles en la estabilidad de los recipientes. Todo ello, a traves del estudio electroquimico individual de los materiales con los cuales son fabricados los recipientes de hojalata, mediante medidas de polarizacion potenciondinamicas e impedancia electroquimica. PALABRAS CLAVES: citrato, corrosion, hojalata, polarizacion potenciodinamica, impedancia electroquimica.

Wstęp Ze względu na swoje własności mechaniczne, zdolność do nadawania kształtów oraz niską cenę w porównaniu z innymi metalicznymi materiałami implantacyjnymi (stopy tytanu i kobaltu) stal nierdzewna jest często używanym materiałem implantacyjnym. Jednak, podczas długotrwałego kontaktu z tkankami ludzkimi następują procesy korozyjne na powierzchni stali związane z niepożądanym uwalnianiem jonów metali takich jak: żelazo, chrom i nikiel [1]. Korozja i proces uwalniania jonów powodują nie tylko uszkodzenia mechaniczne implantów, ale również odczuwania bólu w pobliżu wszczepionego implantu. Dlatego też implanty wymagają specyficznego rodzaju obróbki powierzchniowej w celu zminimalizowania szkodliwych zjawisk [2]. Obecnie, powłoki polimerowe wykorzystywane są do modyfikacji

Phenyltetrazole substituted compounds, namely 5-phenyl-1H-tetrazole (PT), 5-(4chlorophenyl)-1H-tetrazole (Cl-PT), 5-(4-methoxyphenyl)-1H-tetrazole (MO-PT) and 5-p-tolyl-1H-tetrazole (M-PT) were synthesized to study their inhibition behavior on mild steel in 1 M HCl by weight loss measurement, potentiodynamic polarization studies and electrochemical impedance spectroscopy (EIS). It has been observed that corrosion rate decreases and inhibition efficiency increases with increasing in phenyltetrazole substituted concentration and dependence on molecular structure. Polarization data indicate that these compounds act as very good cathodic inhibitors of mild steel in 1 M HCl. The result showed that the inhibition efficiency decreased with temperature and increased with immersion time. EIS has the same trend of inhibitive effect as that of the polarization data, which indicates the formation of a protective layer on mild steel surface by molecules adsorption.

Perfluorocarbons are important contributors to aluminum production greenhouse gas inventories. Tetrafluoromethane and hexafluoroethane are produced in the electrolysis process when a harmful event called anode effect occurs in the cell. This incident is strongly related to the lack of alumina and the current distribution in the cell and can be classified into two categories: high-voltage and low-voltage anode effects. The latter is hard to detect during the normal electrolysis process and, therefore, new tools are necessary to predict this event and minimize its occurrence. This paper discusses a new approach to model the alumina distribution behavior in an electrolysis cell by dividing the electrolytic bath into non-homogenous concentration zones using discrete elements. The different mechanisms related to the alumina distribution are discussed in detail. Moreover, with a detailed electrical model, it is possible to calculate the current distribution among the different anodic assemblies. With this information, the model can evaluate if low-voltage emissions are likely to be present under the simulated conditions. Using the simulator will help the understanding of the role of the alumina distribution which, in turn, will improve the cell energy consumption and stability while reducing the occurrence of high-and low-voltage anode effects.

The advantages of nanostructured cemented carbides are a uniform, homogenous microstructure and superior, high uniform mechanical properties, which makes them the best choice for wear-resistant applications. Wear-resistant applications in the chemical and petroleum industry, besides mechanical properties, require corrosion resistance of the parts. Co as a binder is not an optimal solution due to selective dissolution in an acidic environment. Thus, the development of cemented carbides with alternative binders to increase the corrosion resistance but still retaining mechanical properties is of common interest. Starting mixtures with WC powder, grain growth inhibitors GGIs; VC and Cr3C2, and an identical binder amount of 11-wt.% were prepared. GGIs were added to retain the size of the starting WC powder in the sintered samples. The parameters of the powder metallurgy process were adapted, and samples have been successfully consolidated. A very fine homogeneous microstructure with rela...

Galvanic corrosion of steel/aluminium hybrid joints, obtained by self-piercing riveting technique, was investigated. Potentiodynamic polarisation tests, performed in 3?5 wt-% NaCl solution, evidenced the anodic and cathodic behaviour of metal constituent of the joints. Furthermore, long term aging tests were performed to evaluate the relationship among failure mechanism, joint configuration and corrosion damage in salt spray environment. The experimental results evidenced that the degradation phenomena influenced significantly performances and failure mechanisms of the joints, inducing premature failure of the joint at lower stress level at increasing aging time. Furthermore a theoretical model was proposed to forecast failure modes. Based on this model a simplified map of failure mechanisms promoted by corrosion phenomena has been drawn.

The demand for new welding technologies in civil engineering and transport is increasing. An example of this is the tendency to increase the operating range of a mobile platform mounted on motor vehicles while maintaining the weight of the vehicle. The most commonly used material in the production of mobile platforms are AHSS steels due to their high tensile strength at the level of 1400 MPa. However, the joints created with their use are characterized by much lower strength than the native material. In this article, the most appropriate parameters for welding elements of a mobile platform from difficult-to-use steel AHSS were selected.

The effects of rapid pulse electric current sintering (PECS), Ni as a Co binder substitute, Mo 2 C additions and laser surface modification (LSM) on the microstructure, mechanical properties and machining performance during roughing and finishing turning of Ti-6Al-4 V were investigated. Additions of Mo 2 C reduced the carbide grain size from 0.65 ± 0.01 μm to 0.5 ± 0.01 μm in liquid phase sintered (LPS) WC-Co/Ni cermets, with the PECS manufactured WC-0.5Cr 3 C 2-3.5Mo 2 C-10Co (wt%) having the highest hardness. The LSM technique produced ã 2.5 μm self-carbide coating, increasing the surface hardness of all the samples. LSM was done to improve abrasion, attrition and thermal wear resistance. Turning was done at cuttings speeds (v c) of 45-120 m/min, depths of cut (a p) of 0.25-2.0 mm and feeds of 0.15-0.2 mm/revolution, under lubricated conditions. The developed inserts were compared to TH10 (an industrial reference), and performance was assessed by cutting forces, tool wear and tool life. The liquid phase sintered WC-0.5Cr 3 C 2-10Co (wt%) and WC-0.5Cr 3 C 2-3.5Mo 2 C-10Co (wt%) inserts had longer tool lives than TH10 during roughing at a cutting speed (v c) of 45 m/min, depth of cut (a p) of 2 mm and feed of 0.2 mm/revolution, although TH10 had the best tool life during finishing (v c = 120 m/min, a p = 0.25 mm and feed =0.15 mm/revolution). Generally, LSM had a negligible effect on tool life, WC-Ni based inserts had the shortest tool lives and LPS inserts performed better than PECS inserts.

Corrosion resistance behaviour of duplex (α β) brass (65-35% Cu-Zn alloy) was evaluated in different nitric acid and nitric acid-chloride concentrations. The experiments were performed at ambient temperature using potentiodynamic polarization measurement. Various results obtained are presented in the Tables and curve figures. This paper reports the observed electrochemical response of the experimental tests. Different concentrations of the test media were used with and without sodium chloride addition. Tafel and polarization resistance calculations/ measurements were used to estimate the corrosion rate and polarisation resistance of the alloy samples tested. The results obtained showed varied magnitude of corrosion susceptibility of the brass alloy in HNO3 concentrations and its acid chloride test environments.

We examined the kinetic and transport processes involved in Mg production from MgO via electrolysis at ca 1250 K with in a eutectic mixture of MgF 2-CaF 2 , using a Mo cathode, and carbon anode. Exchange current densities, transfer coefficients, and diffusion coefficients of the electroactive species were established using a combination of cyclic and linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The cathode kinetics are described by a concentration dependent Butler-Volmer equation. The exchange current density and cathodic transfer coefficient are 11 ± 4 A cm-2 and 0.5 ± 0.12 respectively. The kinetics of the anode are described by two Tafel equations: at an overvoltage below 0.4 V, the exchange current density is 0.81 ± 0.2 mA cm-2 with an anodic transfer coefficient of 0.5 ± 0.1; above 0.4 V overvoltage the values are 0.14 ± 0.05 mA cm-2 and 0.7 ± 0.2 respectively. The diffusion coefficients of the electroactive species are D(Mg 2+) = 5.2 ± 0.6 E-5 cm 2 s-1 and D(Mg 2 OF 4 2-) = 7.2 ± 0.2 E-6 cm 2 s-1. The ionic conductivity of the electrolyte is ca 2.6 S cm-1 .

Welding is commonly used for connecting steel components in steel bridge fabrication and construction. Welding processes change the microstructures, properties of surrounding steel and its surface texture. In this study, an investigation of corrosion behavior of steel bridge welds was performed under simulated corrosive environments in the laboratory. Four electrochemical tests: a) open circuit potential, b) Rp/Ec Trend, c) electrochemical impedance spectroscopy and d) potentiodynamic polarization, were identified and conducted to gain fundamentals to weldment corrosion in two commonly used bridge steels (A572 and A588). In addition, three coating systems (3-coat, Calcium sulfonate alkyd, and metallizing coating) in steel bridges were deposited on the bridge steels. Test results revealed that the bridge steel welds exhibit higher corrosion initiation over base metals, regardless the types of steel or coating. The protective coating systems can delay the corrosion initiation at the welds, thus enhancing the corrosion resistance of bridge steel welds. iv ACKNOWLEDGMENTS I would like to express my deepest gratitude to my advisor Dr. Zhibin Lin for his continuous encouragement, patience, and motivation. His guidance supported me in this research and writing this thesis. I would also like to thank my committee member, Dr. Yechun Wang who gave me a lot of support and suggestion. Many thanks also for my committee member, Dr. Fardad Azarmi for his generous support and coating material supply, and Dr. Mijia Yang for his motivation and encouragement in NDSU. I would also like to thank my peers in Dr. Lin's group: Fei Yan (PhD student), Mohsen Azimi (PhD student), Mingli Li (PhD student) and Xingyu Wang (MS student), for their support and valuable suggestion. My sincere appreciation for all supports throughout my research: special thanks to Contech Engineered solution LLC for bridge steel donation, Watson coating, INC. for CSA coating samples, Pacific Painting Company and NDDOT for 3-coat samples, Coating and Polymer department and Dr. Xiaoning Qi who gave us valuable suggestion and help. Special appreciation for helps from Dr. Mehdi Salimi Jazi from mechanical engineering department and undergraduate student, Jason Lange, from Chemistry department. v DEDICATION To My father Adel Kasasbeh My mother Saharieh Dalaeen My brothers and sisters My fiancée Ala'a Alemaryeen My uncle Monther Dalaeen My uncle Natheer Dalaeen My aunts Dalaeen My uncle Eng. Tarq Dalaeen My uncle Neaz Jawazneh Jordanian pilot Moath Kasasbeh My beloved country Jordan vi TABLE OF CONTENTS

Some types of anodes that could replace the usual carbon anodes in aluminium production by the Hall-Heroult process are based on SnO 2. The present investigation deals with SnO 2-Sb 2 O 3-CuO ceramics having an SnO 2 content of 96%), Sb 2 O 3 and CuO being dopants. The ceramic pellets, thermally treated at 1400 C for 4 hours, were analysed by X-ray diffraction and IR spectroscopy. The structural analysis of the samples evidenced an SnO 2 (ss) type solid solution. All samples were electronically conductive (small negative values of the Seebeck coefficients), having an activation energy ranging within 0.02-0.3 eV. The anodic polarisation curves obtained with those anodes in an electrolyte of 88% Na 3 AlF 6 , 7% Al 2 O 3 and 5% CaF 2 were studied. The results were correlated with the microstructure of the investigated samples.

Mixed connections made of normal-strength and high-strength structural steels allow for optimized material usage and production effort in applications where, as a result of different mechanical effects on materials of the same type, it would otherwise be necessary to adjust the plate thickness. Reduced material consumption and smaller weld geometries can thus generate ecological and economic advantages. When welding high-strength structural steels, however, significant softening can occur in the heat-affected zone, which can influence the load-carrying behavior of the overall joint. Since there are currently no appropriate standards for butt welds made of steels with different strengths up to S960, a separate design concept is required. In this paper, the weldability and load-carrying capacity of multilayer MAG welded butt joints designed as mixed connections of a normal-strength structural steel S355 and a high-strength structural steel in the range S690 to S960 are investigated. E...

h i g h l i g h t s Utilization of Ti-based nanostructures for modification of cement paste. TiN thin films effectively provide physical protection to reinforcing steel in concrete against chloride-induced corrosion. The cement paste in contact with TiN develops adhesion phases which enrich the passive layer.

With the anticipated decrease in available anode raw materials, future anodes are expected to contain higher levels of impurities. Currently the implications of this are being investigated through evaluation of electrochemical performance of anodes and the environmental aspects through gas evolution studies. In this work, four experiments of aluminum smelting have been conducted with anodes of varying sulphur content. The aim of this work was to evaluate the speciation of sulphur in the off-gas. It was found that COS is the main sulphur species in the inert argon furnace atmosphere. The gas composition was further evaluated as a function of set anode voltages in potentiostatic mode. The significance levels of gas composition were evaluated through repeated experiments. As an FTIR multicomponent analyzer was used, less commonly discussed gaseous constituents such as CH4 and HCl were evaluated with respect to given impurity levels in the anode.

The effectiveness of inhibitor extract of Trigona sp. propolis (IETP) as the corrosion inhibition of API 5L Grade B steel was studied in the corrosive environment of 3.5% NaCl solutions is systematically presented. The use of selected organic corrosion inhibitors is a new alternative as one type of inhibitor that is non-toxic, inexpensive, available in nature, and environmentally friendly. IETP as an organic corrosion inhibitor has been characterized and analyzed in this study. The main compound in the inhibitor was identified based on the Fourier transform infrared spectroscopic analysis. The chemical compound of the propolis solution is flavonoid-rich in oxygen atoms, which play an important role in the inhibition process. Inhibition behavior was investigated through weight loss testing and the polarization methods on API 5L Grade B steel material in 3.5% NaCl media with variations of the addition of inhibitors 0 ml, 2 ml, 4 ml, 6 ml, 8 ml, and 10 ml into the solution. The results showed that the IETP was quite effective in corrosion medium with a solution of NaCl 3.5%. The 10 ml IETP had the highest effect decreasing the corrosion rate from 3.469 to 2.272 mpy. Optimal and effective levels in the use of IETP is 10 ml with the highest level efficiency of 79%. The polarization curve through the potentiodynamic technique showed that the inhibitor has a tendency for the cathodic inhibitor mechanisms by absorption and simply blocking the reaction on the metal surface.

Three novel Schiff bases, namely N-(4-((4-((phenylimino)methyl)phenoxy)methoxy)benzylidene)benzenamine (UA), N-(3-methoxy-4-((2-methoxy-4-((phenylimino)methyl)phenoxy)methoxy)benzylidene)benzenamine (UB), and N-(3-ethyl-4-((2-ethyl-4-((phenylimino)methyl)phenoxy)methoxy)benzylidene)benzenamine (UC), were synthesized and their structures were elucidated through diverse spectroscopic techniques such as FT-IR, GC-MS, 1 H NMR and 13 C NMR. The corrosion inhibition effect of these Schiff bases on aluminum alloy AA2219-T6 in acidic medium was explored using weight loss, Tafel polarization, and electrochemical impedance spectroscopy. Theoretical quantum chemical calculations using density functional theory were employed to determine the adsorption site. It was found that inhibition efficiencies increase with an increase in the inhibitor concentration. Tafel plots showed that these Schiff bases function as mixed inhibitors. Adsorption of the Schiff bases on aluminum followed the Langmuir adsorption isotherm and the value of DG ads showed a dominant chemical mechanism. FT-IR and SEM techniques were used to investigate the surface morphology. The compounds showed a substantial corrosion inhibition for aluminum alloy in 0.1 M HCl at 298 K. UB and UC exhibited superior anticorrosion efficiency compared to UA originating from the electron-donating methoxy and ethoxy group substitutions, respectively. There was found to be good correlation between molecular structure and inhibition efficiencies.

Electrochemical Impedance Spectroscopy (EIS) is a highly sensitive characterization technique used to establish the electrical response of chemical systems in a nondestructive manner. EIS systems characterize the time response of chemical systems using low amplitude alternating current (AC) voltages over a range of frequencies. Using an electrode setup consisting of a working, reference, and counter electrodes a known voltage is passed from the working electrode through an electrolytic solution and into the counter electrode. Quantitative measurements are produced by the EIS and enable the evaluation of small scale chemical mechanisms at the electrode interface and within the electrolytic solution. Therefore, EIS is useful in determining a wide range of dielectric and electrical properties of components in research fields studying batteries, corrosion, etc. Experimental Set Up An electrochemical cell is used to house the chemical reaction and is electrically connected to the electrochemical spectrometer to obtain the electrical response of an electrolytic solution. EIS systems are operated using computer programs specifically designed for EIS testing. Therefore, prior to conducting an EIS experiment it is essential that all components of the system be attained. Generally, EIS studies utilize a three electrode mode which is comprised of a working electrode (the sample material), a counter electrode (commonly graphite or platinum), and a reference electrode. While electrode geometries may vary the general experimental setup remains similar to the procedure outlined below. The three electrodes are mounted on an electrode stage and secured. The electrolytic solution is prepared and transferred to the sample container. A metallic sample container would provide additional pathways for electrons during experimentation leading to a reduction in the EIS current response as electrons move into the metal rather than the reference electrodes. Therefore, the sample container should be composed of an insulating material, such as glass or

The inhibitory effect of 3a,6a-diphenyltetrahydro-1H-imidazo [4,5-c] [1, 2, 5] thiadiazole-5(3H)-thione 2,2-dioxide (TTU) on the corrosion behaviour of mild steel in 0.5 M H 2 SO 4 , at (30 ± 0.5)°C was studied by gravimetric, potentiodynamic polarization, electrochemical impedance spectroscopy, and scanning electron microscopy measurements. The effect of inhibitor concentration on the corrosion rate, surface coverage and inhibition efficiency is investigated. Results show that TTU exerts a strong inhibiting effect on mild steel corrosion and acts as a cathodic-type inhibitor. TTU does not affect the mechanism of the cathodic reaction while the anodic reaction mechanism changes upon addition of the inhibitor. Possible mechanistic pathways for the inhibition process are proposed. The inhibition efficiency of TTU may be due to either the adsorption of inhibitor molecules building a protective film or the formation of an insoluble complex of the inhibitor with metal cations. TTU adsorption obeys the Langmuir model.

The anti-corrosion characteristics of reactive blue dye for mild steel in 1N H2SO4 was investigated using weight loss and potentiodynamic polarization studies. Corrosion parameters such as inhibition efficiency, corrosion rates, corrosion potential corrosion current and Tafel slopes were evaluated. The inhibition efficiency was found to increase with increase in the inhibitor concentration.

The inhibitive action of the extract of the roots and fruits of Aegle marmelos was investigated as a green corrosion inhibitor for zinc in 0.5N H2SO4 employing weight loss, gasometric and thermometric methods. The results obtained revealed that the extract of the plant could be employed as an effective inhibitor for the corrosion of zinc in sulphuric acid medium.. The inhibition efficiency of the extract increased with increase in its concentration. The adsorption of the inhibitor molecules on the zinc metal surface obeyed Temkin adsorption isotherm.

In this work, dipropyl sulphide was evaluated as a corrosion inhibitor for zinc in 0.5N sulphuric acid by weight loss, gasometry and thermometry methods. Results obtained revealed that the inhibitor performed well in the acid solution. The inhibition efficiency increased with increase in the concentration of the inhibitor. The adsorption of the inhibitor molecules on the zinc metal surface obeyed Temkin adsorption isotherm.

The amino acid, cystein was examined as an inhibitor for zinc in 0.5N HCl was using weight loss and potentiodynamic polarization studies. Corrosion parameters such as inhibition efficiency, corrosion rates, corrosion potential and corrosion current were evaluated. The inhibition efficiency was found to increase with increase in the inhibitor concentration. The adsorption of the inhibitor on the zinc surface followed Temkin adsorption isotherm.

Magnesium is potentially useful for orthopaedic and cardiovascular applications. However, the corrosion rate of this metal is so high that its degradation occurs before the end of the healing process. In industrial media the behaviour of several magnesium alloys have been probed to be better than magnesium performance. However, the information related to their corrosion behaviour in biological media is insufficient. The aim of this work is to study the influence of the components of organic fluids on the corrosion behaviour of Mg and AZ31 and LAE442 alloys using potentiodynamic, potentiostatic and EIS techniques. Results showed localized attack in chloride containing media. The breakdown potential decreased when chloride concentration increased. The potential range of the passivation region was extended in the presence of albumin. EIS measurements showed that the corrosion behaviour of the AZ31 was very different from that of LAE442 alloy in chloride solutions.

Magnesium is potentially useful for orthopaedic and cardiovascular applications. However, the corrosion rate of this metal is so high that its degradation occurs before the end of the healing process. In industrial media the behaviour of several magnesium alloys have been probed to be better than magnesium performance. However, the information related to their corrosion behaviour in biological media is insufficient. The aim of this work is to study the influence of the components of organic fluids on the corrosion behaviour of Mg and AZ31 and LAE442 alloys using potentiodynamic, potentiostatic and EIS techniques. Results showed localized attack in chloride containing media. The breakdown potential decreased when chloride concentration increased. The potential range of the passivation region was extended in the presence of albumin. EIS measurements showed that the corrosion behaviour of the AZ31 was very different from that of LAE442 alloy in chloride solutions.