Electrochemical Corrosion

The corrosion rate of AZ31, AZ80, and AZ91D magnesium/aluminium alloys immersed in 3.5 wt.% NaCl was determined comparing gravimetric and electrochemical measurements. The findings revealed that, for all investigated materials, a fraction of the metallic surface exposed to the corrosive medium did not reveal a normal electrochemical response to the applied signal. This may be associated with phenomena such as partial disintegration of specimens into fine metallic particles, electrochemical formation of ions, and/or anomalous chemical attack occurring simultaneously with the normal electrochemical corrosion attack. The abnormal electrochemical behaviour was more evident for lower amounts of aluminium in the bulk composition of the investigated materials. Thus, the electrochemical estimates of pure Mg and the AZ31 alloy were not reliable and tended to underestimate corrosion losses.

The corrosion behaviours of naturally aged and artificially aged AA2024 aluminium alloys in 0.5 mol/dm 3 NaCl solution in the presence of environmentally friendly corrosion inhibitors of 10 mmol/dm 3 CeCl 3 , 10 mmol/dm 3 BTA and the inhibitor mixture (5 mmol/dm 3 CeCl 3 + 5 mmol/dm 3 BTA) were analyzed. The goal of this work was to determine the level of the synergistic effect of the inhibitor mixture and to explain the nature of this effect. Corrosion properties of the inhibitor layer were studied using the electrochemical impedance spectroscopy (EIS), while the resistance to pit formation and pit growth was studied by applying potentiodynamic polarisation tests. The results of scanning electron microscopy (SEM/EDS) showed that the size of pits formed in naturally aged aluminium alloy was smaller than that formed in artificially aged alloy. The synergistic effect of the inhibitor mixture on corrosion properties of naturally aged alloy was observed throughout 96 h, and in later phases of testing of artificially aged alloy. The synergistic effect of the inhibitor mixture was not noticed on pit formation and pit growth.

The protective performance of a sand particle-modified enamel coating on reinforcing steel bars was evaluated in 3.5 wt% NaCl solution by electrochemical impedance spectroscopy (EIS). Seven percentages of sand particles by weight were investigated: 0%, 5%, 10%, 20%, 30%, 50% and 70%. The phase composition of the enamel coating and sand particles were determined with the X-ray diffraction (XRD) technique. The surface and cross-sectional morphologies of the sand particle-modified enamel coating were characterized using scanning electron microscopy (SEM). XRD tests revealed three phases of sand particles: SiO 2 , CaCO 3 and MgCO 3 . SEM images demonstrated that the enamel coating wetted well with the sand particles. However, a weak enamel coating zone was formed around the sand particles due to concentrated air bubbles, leading to micro-cracks as hydrogen gas pressure builds up and exceeds the tensile strength of the weak zone. As a result, the addition of sand particles into the enamel coating reduced both the coating and corrosion resistances.

Silver nanowires (AgNW) are new nanomaterials designed to be incorporated into transparent conductive films in electronics, microelectrodes, heated surfaces and others. Although in these films, the AgNW are generally protected by a coating material, a risk for release of silver at all stages of the nanoproduct life cycle does exist due to corrodibility of the metal. Since ionic and nanoparticulate Ag represent a toxicological risk for a large number of living cells, there is a need for quantifying the potential Ag release from these product components. We developed an electrochemical method to evaluate possible corrosion activity of silver in AgNW transparent conductive films (TCFs) and concomitant Ag + release. A polysiloxane polymer was used as protective coating of AgNW TCFs. A consistent correlation is observed between the degree of corrosion and the coatings' characteristics, in particular the thicknesses. A major advantage of the new approach, compared to classical aging studies, is the short experimentation time: 20 min are sufficient for a diagnostic result. The method is an accelerated corrosion and release test. It is green methodology with use of very low electric power and with no harmful reagents. A particularly attractive application could be in the field of environmental risk assessment of metals from portable electronics and biosensors.

The article examines the plasma sprayed 80Ni-20Al coatings on aluminum-magnesium (Mg ≈ 2.6‒3.6 %) alloy substrate, which before plasma spraying was cleaned using blasting with Al2O3 particles. The wear resistance and corrosion tests of sprayed coating and aluminum-magnesium alloy were performed. The volume loss, average central part of the cross-sectional area of wear track, wear rapidity, wear rate, wear resistance and corrosion current of coating and Al-Mg substrate were evaluated. The wear resistance and corrosion of nickel-aluminum coating and aluminum-magnesium substrate were compared at the work. Furthermore the wear tracks analysis of sprayed coating and substrate surface was carried out.

In this research the effect of Al2O3 nanoparticles on corrosion behavior of aluminum base alloy (Al-4.5 wt% Cu-1.5 wt% Mg) has been investigated. Nanocomopsites reinforced with variable contents of 1, 3 and 5 wt% of Al2O3 nanoparticles were fabricated using powder metallurgy. All samples were prepared from the base alloy powders under the best powder metallurgy processing conditions of 6 hr of mixing time, 450 MPa of compaction pressure and 560 °C of sintering temperature. Density and micro hardness measurements, and electrochemical corrosion tests are performed for all prepared samples in 3.5 wt% NaCl solution at room temperature using potentiostate instrument. It has been found that density and micro hardness of the nanocomposite increase with increasing of wt% Al2O3 nanoparticles to Al matrix. It was found from Tafel extrapolation method that corrosion rates of the nanocomposites reinforced with alumina nanoparticles were lower than that of base alloy. From results of corrosion t...

Silver nanowires (AgNW) are new nanomaterials designed to be incorporated into transparent conductive films in electronics, microelectrodes, heated surfaces and others. Although in these films, the AgNW are generally protected by a coating material, a risk for release of silver at all stages of the nanoproduct life cycle does exist due to corrodibility of the metal. Since ionic and nanoparticulate Ag represent a toxicological risk for a large number of living cells, there is a need for quantifying the potential Ag release from these product components. We developed an electrochemical method to evaluate possible corrosion activity of silver in AgNW transparent conductive films (TCFs) and concomitant Ag + release. A polysiloxane polymer was used as protective coating of AgNW TCFs. A consistent correlation is observed between the degree of corrosion and the coatings' characteristics, in particular the thicknesses. A major advantage of the new approach, compared to classical aging studies, is the short experimentation time: 20 min are sufficient for a diagnostic result. The method is an accelerated corrosion and release test. It is green methodology with use of very low electric power and with no harmful reagents. A particularly attractive application could be in the field of environmental risk assessment of metals from portable electronics and biosensors.

The corrosion rate of AZ31, AZ80, and AZ91D magnesium/aluminium alloys immersed in 3.5 wt.% NaCl was determined comparing gravimetric and electrochemical measurements. The findings revealed that, for all investigated materials, a fraction of the metallic surface exposed to the corrosive medium did not reveal a normal electrochemical response to the applied signal. This may be associated with phenomena such as partial disintegration of specimens into fine metallic particles, electrochemical formation of ions, and/or anomalous chemical attack occurring simultaneously with the normal electrochemical corrosion attack. The abnormal electrochemical behaviour was more evident for lower amounts of aluminium in the bulk composition of the investigated materials. Thus, the electrochemical estimates of pure Mg and the AZ31 alloy were not reliable and tended to underestimate corrosion losses.

The corrosion behaviours of naturally aged and artificially aged AA2024 aluminium alloys in 0.5 mol/dm 3 NaCl solution in the presence of environmentally friendly corrosion inhibitors of 10 mmol/dm 3 CeCl 3 , 10 mmol/dm 3 BTA and the inhibitor mixture (5 mmol/dm 3 CeCl 3 + 5 mmol/dm 3 BTA) were analyzed. The goal of this work was to determine the level of the synergistic effect of the inhibitor mixture and to explain the nature of this effect. Corrosion properties of the inhibitor layer were studied using the electrochemical impedance spectroscopy (EIS), while the resistance to pit formation and pit growth was studied by applying potentiodynamic polarisation tests. The results of scanning electron microscopy (SEM/EDS) showed that the size of pits formed in naturally aged aluminium alloy was smaller than that formed in artificially aged alloy. The synergistic effect of the inhibitor mixture on corrosion properties of naturally aged alloy was observed throughout 96 h, and in later phases of testing of artificially aged alloy. The synergistic effect of the inhibitor mixture was not noticed on pit formation and pit growth.

 The Ti-6Al-4V alloy is fabricated by electron beam melting (EBM) technology;  The electrochemical corrosion behaviour of EBM-produced Ti-6Al-4V is investigated;  A larger proportions of β phase and ultrafine-grained lamellar α/β phases are observed in the microstructure of EBM-produced Ti-6Al-4V;  EBM-produced Ti-6Al-4V possesses slightly better corrosion resistance than the traditional wrought Ti-6Al-4V.

Magnesium alloys have been widely used as lightweight engineering structural materials, but their service performances are severely restricted by corrosion failure. In this paper, the influence of corrosive medium and surface defect energy on the corrosion behavior of rolled ZK61M alloy was investigated. The corrosion tests were conducted in different concentrations of sodium chloride solution for different durations, and the polarization curves and electrochemical impedance spectroscopy were reported. The surface morphology of rolled ZK61M alloy before and after corrosion tests were analyzed. The results showed that the corrosion tendency became stronger with the increase of the concentration of corrosive medium and the number of surface defects of ZK61M alloy. Moreover, the initial corrosion pattern was the pitting caused by micro galvanic corrosion at the surface defect, which gradually developed into uniform corrosion. Furthermore, the main damage occurred at the grain boundary,...

As known, large structural refinements can be achieved through imposing deformation by the simple shear. Severe plastic deformation (SPD) methods are one of the pronounced metal-forming processes which utilize this phenomenon to produce ultrafine-grained (UFG) or even nanostructured (NS) metals and alloys [1]. Usually, SPD methods are described as a process in which high hydrostatic pressure is applied in bulk a r c h i v e s o f c i v i l a n d m e c h a n i c a l e n g i n e e r i n g 1 9 (2 0 1 9) 8 4 2-8 5 0

Stainless steel (SS) grade 316L is used for orthopedic implants due to its biocompatibility; yet the effort should be done to minimize the carcinogenic and inflammatory effects related to SS 316L implants. In this research, aluminide coating of Al-Si alloy on SS 316L is characterized by using optical microscopy, energy dispersive spectroscopy (EDS), nano-indentation and corrosion testing technique. Hot dip aluminizing process is used to coat the SS 316L specimens at 765 °C for 2 min immersion time. Half of the specimens are also diffusion treated in a Muffle furnace at 550 °C for 4 h to produce diffused specimens of SS 316L. Microstructural examination shows the formation of flat coating/substrate interface due to Si addition. EDS analysis confirms the formation of complex intermetallic at the coating/substrate interface which finally results in increasing the hardness and corrosion resistance properties of coating.

Nowadays, the aluminum alloys find various applications, such as production of lightened aircrafts, automobiles and stationary (i.e. pipelines) transport facilities, as well as high voltage, large distance energy transmission via aluminum cables. Recently, various sensor elements and alternative energy sources have been developed on the basis of anodized aluminum details. Furthermore, some aluminum alloys are widely used for packaging of nutrition products and soft drinks. However, the reliable use of these alloys demands elaboration of advanced surface treatment methods, in order to supply satisfactory durability and reliability of the respective aluminum products. In this sense, the present study provides information on the influence of the alloying elements and the anionic components of four commonly used acids: HNO 3 , H 3 PO 4 , H 2 SO 4 , and HCl on the AA2024-T3 surface morphology during galvanostatic anodic polarization in the corresponding media.

The present investigation of potential metric techniques in the determination of the corrosion rate of AISI 304 stainless steel, has been possible through the use of the potentiostat that has a measurement range of 0.005 mA to 1,000 mA with responses in the potentials of 0.1 at 100 mV. The corrosion rates of AISI 304 stainless steel have been determined: medium: 3.56% C.R. sodium chloride solution. (mpy) = 1.72 medium: synthetic sea water C.R. (mpy) = 1.28. The study of corrosion rate measurement in engineering material, using the potentiostat has proven to be fast and reliable.La presente investigación de técnicas potencio métricas en la determinación de la velocidad de corrosión del acero inoxidable AISI 304, ha sido posible mediante el uso del potenciostato que tiene un rango de medición de 0,005 mA a 1,000 mA con respuestas en los potenciales de 0,1 a 100 mV. Las velocidades de corrosión del acero inoxidable AISI 304 ha sido determinado: medio: solución de cloruro de sodio al 3,...

Corrosion is one of the main causes of incidents occurred in hazardous liquid and gas transmission pipelines in the USA, resulting in a loss of over $12 billion per year. In this study, the corrosion resistance of pipeline steel coated with five types of enamel was investigated in 3.5 wt% NaCl solution with linear polarization resistance and electrochemical impedance spectroscopy tests. Steel coupons were cut from API 5L X65 pipeline steel and coated with five types of enamels using the wet process. The microstructures of all enamel samples were examined by scanning electron microscopy. Experimental results indicate that all enamel coatings increase the corrosion resistance of pipeline steel, and pure enamel PE2, mixed enamels ME1 and ME2 have higher corrosion resistances than pure enamel PE1 and mixed enamel ME3.

Metallic biomaterial like stainless steel, Co- based alloy, Ti and its alloy are widely used as artificial hip joints, bone plates and dental implants. However; this alloy releases ions from the surface liable to do serious harm to human bodies. For overcoming surface originated problems, various surface modification technique have been used on the metallic implants. In this study, the nitrogen was implanted by a process of ion implantation at 60 keV with different fluences of 1 x 10 16, 5 x 10

Severe Plasic Deformation of Aluminium using Equal Channel Angular Pressing. The ultrafine grained metallic materials are widely investigated during the past years with a view to the opportunities for various industrial applications of their improved mechanical and technological properties. Most of them are produced by using severe plastic deformation which allows large bulk samples to be obtained. This paper presents some preliminary results for aluminium processed by equal channel angular pressing.

Severe Plasic Deformation of Aluminium using Equal Channel Angular Pressing. The ultrafine grained metallic materials are widely investigated during the past years with a view to the opportunities for various industrial applications of their improved mechanical and technological properties. Most of them are produced by using severe plastic deformation which allows large bulk samples to be obtained. This paper presents some preliminary results for aluminium processed by equal channel angular pressing.

The corrosion behaviour of 6082 aluminium alloy was studied by measuring the
electrochemical impedance spectra and electrode polarization curves. After the
electrochemical tests, a microstructural analysis of the samples was conducted
by using optical microscopy and electron scanning microscopy techniques to
determine the corrosion mechanism. The results show that the Nyquist plot of
the electrochemical impedance data in the NaCl solution consists of high‐ and
low‐frequency capacitive impedance loops. When SO24− ions are added to the
NaCl etchant, the Nyquist plots of the electrochemical impedance data are
composed of two different curves: a high‐frequency capacitive impedance loop
and a low‐frequency inductive impedance loop. The corrosion current density
increases with increasing SO24− concentration, and as a result, the corrosion
resistance of the aluminium alloy decreases. The microstructures of 6082
aluminium alloy consist of Mg2Si secondary particles in a large α‐Al matrix.
Pitting corrosion initially occurs at the boundary between the matrix and
secondary particles because the electrode potentials of the matrix and secondary
particles are different. Then, corrosion paths develop along the network‐like
grain boundaries, and finally, massive network‐like corrosion occurs throughout the entire alloy.

Stress corrosion tests of 6082 aluminum alloy were carried out by using a three‐point
bending fixture while holding at 50% of yield strength state through different
immersion times in 1.5% NaCl electrolyte solution. The electrochemical impedance
spectra and dynamic electric potential polarization curves were measured to indicate
the stress corrosion behavior of the alloy. Optical microscopy, scanning electron
microscopy, and X‐ray energy spectrum analysis were applied for microstructural
investigations. The results show that all of the Nyquist electrochemical impedance
spectra consisted of high‐ and low‐frequency double capacitive arcs. However, an
increase in immersion time while holding at 50% of yield stress resulted in a
corresponding increase in the corrosion current density, leading to gradual corrosion
depth growth, and a decrease in the corrosion resistance of the alloy. 6082
Aluminum alloy included AlMnFeSi, Mg2Si, and Si secondary phases. The different
secondary phases presented different stress corrosion behaviors. Stress corrosion
cracks were generated at the boundaries of AlMnFeSi and matrix or within the
AlMnFeSi phase. Crack direction is always perpendicular to the tensile stress
applied. Mg2Si secondary phase was self‐corroded as its corrosion potential is lower
than that of the matrix. As the electric potential of Si is higher than that of the
matrix, corrosion occurred at the matrix side of the boundary between Si and matrix.
KEYWORDS
6082 aluminum alloy, electrochemical corrosion, secondary phase, stress corrosion

Severe Plasic Deformation of Aluminium using Equal Channel Angular Pressing.
The ultrafine grained metallic materials are widely investigated during the past years with a view to the opportunities for various industrial applications of their improved mechanical and technological properties. Most of them are produced by using severe plastic deformation which allows large bulk samples to be obtained. This paper presents some preliminary results for aluminium processed by equal channel angular  pressing.

Abstract: Severe Plasic Deformation of Aluminium using Equal Channel Angular Pressing. The ultrafine grained metallic materials are widely investigated during the past years with a view to the opportunities for various industrial applications of their improved mechanical ...

Abstract: The objective of this investigation was to define the influence of cold plastic deformation
on the mechanical and magnetic properties of X5CrNi18-10 austenitic steel. A sheet can easily be formed to
complex shapes, but the regions suffering severe deformation will transform to another phases and generate
a high strength. The major drawback of this approach and these materials in general, is the unpredictable
mechanical properties. To predict the properties after deformation and during service it is vital to foresee the
amount of martensite formed during certain conditions.
Key words: chromium–nickel austenitic steel, plastic deformation at low temperature, metallic sheets.

Abstract: The objective of this investigation was to define the influence of cold plastic deformation
on the structure, mechanical and magnetic properties of X5CrNi18-10 austenitic steel. Due to their high
corrosion resistance and versatile mechanical properties the austenitic stainless steels are used for plastic
deformation at low temperature.The formation of deformation-induced martensite is related to the austenite
(γ) instability at temperatures close or below room temperature. However this transformation does not occur
homogeneously in the whole material, since the volume fraction of martensite formed is a function of the
amount of deformation.The aim of this study is therefore to investigate the phase composition, texture and
microstructure to improve the current understanding of the deformation induced martensitic transformation in
X5CrNi18-10 austenitic steel after 43% uniaxial tension.
Key words: chromium–nickel austenitic steel, plastic deformation at low temperature, metallic sheet,
microstructure, XRD.

Solid-state carburizing capacities In the world crises time there is a decrease in the amount
of the metallurgical, machine-building and metal working production. This influence the working conditions in
the companies which turn from large-scale to single-case production. This is the reason for searching
adequate, even old-fashioned but economical methods in machine-building technologies.
The article deals with the solid-state carburizing capacities for treating constructional steels in respect
to increase their endurance and reliability. Carbon saturation of surface welded layers on steel substrates is
investigated. The afterward heat treatment is discussed.
Key words: solid-state carburizing, surface welded layers, heat treatment.

НАУЧНИ ТРУДОВЕ НА РУСЕНСКИЯ УНИВЕРСИТЕТ - 2010, том 49, серия 2 - 60 - Симулиране на процеси на обемно деформиране по метода на крайните елементиВалентин Гагов, Росен Радев, Борис Томов ... [18] Гагов В., Р. Радев, Е. Янков, Д. Господинов. ...

The purpose of the present paper is to examine the surface morphology of laser-melted layers of austenitic stainless steel after electro-chemical corrosion tests in Artificial Saliva (AS). Samples of steel AISI 321 (EN X6CrNiTi 18-10) are subjected to a surface treatment with continuous CO 2 laser, which provides surface melting. After that the electro-chemical corrosion tests in artificial saliva (Fusayama Meyer) with different acidity -pH 5,6 and pH 6,5 were done. The free potentials E f until reaching steady state potentials E ss and potentiodynamic anodic polarization were examined. The surface morphology was observed by SEM and an optical microscope. Two types of corrosion -pitting and crevice were observed on the surface of all the samples regardless of the solution acidity. The pittings formed possess relatively small sizes 150-300 μm and their quantity is larger in laser-melted layers compared to the base metal. During electro-chemical tests in AS with pH 6,5 there is nearly...

Immobilization of amyloid β (Aβ) (1–40) peptide on Au-colloid modified gold electrodes has been studied. Colloidal Au was self-assembled onto gold electrodes through the thiol groups of 1,6-hexanedithiol monolayer. Next, buffered aqueous solution of Aβ (1–40) peptide existing in the β-sheet structure in the acidic media was dropped on the electrode surface. Each step of electrode modification has been confirmed with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The changes of the resistance of the layer with deposited Aβ (1–40) peptide, occurred under stimulation by different concentration of (−) nicotine ditartrate and (−) cotinine were measured with EIS and were used for the calculation of association constants.The gentle measuring conditions applied in electrochemical impedance spectroscopy, together with suitable environment for biomolecules immobilization created by Au-colloid, might be recommended as the analytical tool for assessing the effectiveness of potential drugs used in Alzheimer's disease (AD) therapy.

The genus enterovirus is constituted by a wide number of viral species having in common many of morphological and genetic characters. These viruses present a high epidemiological power and are in question of various human diseases. The absence of easy and standardized technique for their detection justify the need to develop new techniques of diagnosis. In this work, we describe the development of an immunosensor based on functionalized gold electrode allowing enteroviruses detection. The biosensor is based on the grafting of specific monoclonal enterovirus antibodies onto functionalized gold electrode. Each step of biosensor construction was characterised by electrochemical impedance spectroscopy, fitted with an equivalent electric circuit and the antibody-virus interaction was measured with a detection limit of 10 viral particles (vp) or 1.4 vp/mL.

The genus enterovirus is constituted by a wide number of viral species having in common many of morphological and genetic characters. These viruses present a high epidemiological power and are in question of various human diseases. The absence of easy and standardized technique for their detection justify the need to develop new techniques of diagnosis. In this work, we describe the development of an immunosensor based on functionalized gold electrode allowing enteroviruses detection. The biosensor is based on the grafting of specific monoclonal enterovirus antibodies onto functionalized gold electrode. Each step of biosensor construction was characterised by electrochemical impedance spectroscopy, fitted with an equivalent electric circuit and the antibody-virus interaction was measured with a detection limit of 10 viral particles (vp) or 1.4 vp/mL.

The genus enterovirus is constituted by a wide number of viral species having in common many of morphological and genetic characters. These viruses present a high epidemiological power and are in question of various human diseases. The absence of easy and standardized technique for their detection justify the need to develop new techniques of diagnosis. In this work, we describe the development of an immunosensor based on functionalized gold electrode allowing enteroviruses detection. The biosensor is based on the grafting of specific monoclonal enterovirus antibodies onto functionalized gold electrode. Each step of biosensor construction was characterised by electrochemical impedance spectroscopy, fitted with an equivalent electric circuit and the antibody-virus interaction was measured with a detection limit of 10 viral particles (vp) or 1.4 vp/mL.

The genus enterovirus is constituted by a wide number of viral species having in common many of morphological and genetic characters. These viruses present a high epidemiological power and are in question of various human diseases. The absence of easy and standardized technique for their detection justify the need to develop new techniques of diagnosis. In this work, we describe the development of an immunosensor based on functionalized gold electrode allowing enteroviruses detection. The biosensor is based on the grafting of specific monoclonal enterovirus antibodies onto functionalized gold electrode. Each step of biosensor construction was characterised by electrochemical impedance spectroscopy, fitted with an equivalent electric circuit and the antibody-virus interaction was measured with a detection limit of 10 viral particles (vp) or 1.4 vp/mL.