cyclic polarization
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Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 98
Author(s):  
Zheng Dong ◽  
Chuanqing Fu ◽  
Amir Poursaee

The present study investigated the galvanic effect between tensile-stressed and non-stressed carbon steels, in addition to the influence of the tensile stress on the passivation and corrosion behavior of steel in a simulated concrete pore solution. Three different levels of tensile stress, ranging from elastic to plastic stress on the surface, were applied by adjusting the displacement of C-shape carbon steel rings. Different electrochemical measurements including the open circuit potential (OCP), the electrochemical impedance spectroscopy (EIS), the zero-resistance ammetry (ZRA), and the cyclic polarization were performed. Based on the results of EIS, the tensile stress degraded the resistance of the oxide film in moderate frequencies while enhancing the charge transfer resistance in low frequencies during passivation. As corrosion propagated, the stressed steel yielded a similar charge transfer resistance to or an even lower charge transfer resistance than the non-stressed steel, especially in the case of plastic tensile stress. The galvanic effect between the tensile-stressed and non-stressed steels increased the chloride threshold value of the tensile-stressed steel, although the susceptibility to pitting corrosion was exhibited after being corroded.


Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 96
Author(s):  
Ameeq Farooq ◽  
Sohaib Ahmad ◽  
Kotiba Hamad ◽  
Kashif Mairaj Deen

This research work aims to develop electrodeposited Zn-Ni alloy coatings with controlled dissolution tendencies on a mild steel substrate. The varying Ni concentration in the electroplating bath, i.e., 10, 15, 20 and 25 g·L−1, affected the surface morphology and electrochemical properties of the deposited Zn-Ni alloy coatings. SEM and EDS analysis revealed the resulting variation in surface morphology and composition. The electrochemical behavior of different coatings was evaluated by measuring the open circuit potential and cyclic polarization trends in 3.5 wt.% NaCl solution. The degradation behavior of the electrodeposited Zn-Ni coatings was estimated by conducting a salt spray test for 96 h. The addition of Ni in the coating influenced the coating thickness and surface morphology of the coatings. The coating thickness decreased from 38.2 ± 0.5 μm to 20.7 ± 0.5 μm with the increase in Ni concentration. Relatively negative corrosion potential (<−1074 ± 10 mV) of the Zn-Ni alloy coatings compared to the steel substrate (−969 mV) indicated the sacrificial dissolution behavior of the Zn-rich coatings. On the other hand, compared to the pure Zn (26.12 mpy), ~4 times lower corrosion rate of the Zn-Ni coating (7.85 mpy) was observed by the addition of 25 g·L−1 Ni+2 in the bath solution. These results highlighted that the dissolution rate of the sacrificial Zn-Ni alloy coatings can effectively be tuned by the addition of Ni in the alloy coating during the electrodeposition process.


2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Karthika Shetty ◽  
Jayadev ◽  
Kalyan Raj ◽  
H. C. Ananda Murthy

In India, the thermal station generates approximately 6.9 × 10 7 tons of fly ash (FA) as a waste by-product. As part of this work, little attempt was made to produce useful materials from waste material. In our current research, polyaniline- (PANI-) fly ash (FA) nanocomposite (PFNC) was synthesized using an in situ polymerization method. The synthesized composites were characterized by employing advanced analytical, microscopic, and spectroscopic tools. The results of the X-ray diffraction (XRD) analysis confirm the effective reinforcement of FA into PANI in PFNC. The presence of functional groups in PFNC has been confirmed by Raman and FT-IR spectroscopic techniques. The SEM micrographs of the nanocomposite revealed the presence of agglomerated and fragmented structures in PFNC. The weight loss for PFNC was observed to occur in three stages as revealed by thermogravimetric analysis (TGA). UV-visible spectra for PFNC proved that FA stabilized the PANI in emeraldine form. Electrodynamic polarization studies were conducted to explore the corrosion resistance of nanocomposite-coated mild steel. The corrosion current density ( i corr ) for PFNC-coated mild steel (MS) specimens was found to decrease when compared to the bare substrate, indicating superior corrosion resistance in PFNC-coated substrate. Similarly, Tafel and cyclic polarization studies too confirmed superior anticorrosion property for MS coated with PFNC.


Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7912
Author(s):  
Nikola Macháčková ◽  
Jitřenka Jírů ◽  
Vojtěch Hybášek ◽  
Jaroslav Fojt

In the field of orthopedic or dental implants, titanium and its alloys are most commonly used because of their excellent mechanical and corrosion properties and good biocompatibility. After implantation into the patient’s body, there is a high risk of developing bacterial inflammation, which negatively affects the surrounding tissues and the implant itself. Early detection of inflammation could be done with a pH sensor. In this work, pH-sensitive systems based on TiO2-Ru and TiO2-RuO2 combinations were fabricated and investigated. As a base material, Ti-6Al-4V alloy nanostructured by anodic oxidation was used. Ruthenium was successfully deposited on nanotubular TiO2 using cyclic polarization, galvanostatic and potentiostatic mode. Potentiostatic mode proved to be the most suitable. The selected samples were oxidized by cyclic polarization to form a TiO2-RuO2 system. The success of the oxidation was confirmed by XPS analysis. The electrochemical response of the systems to pH change was measured in saline solution using different techniques. The measurement of open circuit potential showed that unoxidized samples (TiO2-Ru) exhibited sub-Nernstian behavior (39.2 and 35.8 mV/pH). The oxidized sample (TiO2-RuO2) containing the highest amount of Ru exhibited super-Nernstian behavior (67.3 mV/pH). The Mott–Schottky analysis proved to be the best method. The use of the electrochemical impedance method can also be considered, provided that greater stability of the samples is achieved.


2021 ◽  
Vol 14 (4) ◽  
pp. 13-25
Author(s):  
Noor Abdulkareem AL-Ali ◽  
Makarim H. Abdulkareem ◽  
Iman Adnan Anoon

In this study, two systems of bio-ceramic coating (45S5 bioactive glass and hydroxyapatite) were used in order to compare between them for biomedical applications. Each system consists from two layers of coating done by electrophoretic deposition (EPD) technique on 316L stainless steel material as substrate. Two types of biopolymer were used (Chitosan with Gelatin) as first layer of coating. Taguchi approach with L9 array was used in order to choose the best conditions (concentrations, voltage and time) for coating layers. Each system consists of two layer (biopolymer (first layer) and bioceramic (second layer)) materials. The optimum parameters for first layer of biopolymer was (3g/L concentration, 20 voltage and 3 minute) while optimum parameter for second layer (6g/L concentration, 30 voltage and 1 minute) for two bioceramic group. Zeta potential test were employed to measure suspensions stability. The tape test method was used to evaluate the adhesion between substrate and coating layers, the results show that the percentage of removal area for optimum coating layer (biopolymer, 45S5 BG and HA   8.06%, 10.668%, 6.23% subsequently). XRD inspection was used for identify the phases of coating layers. The Cyclic polarization test was used for evaluation of pitting corrosion resistance, the results show all layers gives good corrosion resistance but 45S5BG gives the best corrosion resistance when compared with HA system.


Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1516
Author(s):  
El-Sayed M. Sherif ◽  
Ayman H. Ahmed

The alleviation of iron corrosion in 3.5% NaCl sodium chloride solution using N,N′-bis[2-methoxynaphthylidene]amino]oxamide (MAO) as a corrosion inhibitor has been reported. The work was achieved using various investigation techniques. Potentiodynamic cyclic polarization (PCP) displayed a powerful inhibition for the corrosion via reducing the iron’s cathodic and anodic reactions. This was reflected in reduced corrosion currents and increased polarization resistances in the presence and upon the increase of MAO concentration. The electrochemical impedance spectroscopy results indicated that MAO molecules provoke the corrosion resistance via increasing polarization resistance. The power of MAO on decreasing pitting attack was also investigated through measuring the change of current with time at −0.475 V(Ag/AgCl). Scanning electron microscopy images were taken of the surface after the current–time measurements were performed in the absence and presence of MAO. The current-time experiments indicated that MAO highly mitigates the corrosion of iron. The energy dispersive X-ray analyzer reported the products found on the tested surfaces. The effect of extending the exposure time from 1 h to 48 h was also tested and was found to alleviate the corrosion of iron, whether MAO molecules are absent or present.


Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1391
Author(s):  
Hamad F. Alharbi ◽  
Yassir A. Bahri ◽  
El-Sayed M. Sherif

Pure Ti and 85%Ti-15%Zr alloy were sintered in a heat induction high frequency furnace. The corrosion behaviour of Ti and 85%Ti-15%Zr in simulated body fluid (SBF) was studied. The work was achieved using different techniques as the cyclic polarization (PCP), the impedance spectroscopy (EIS), and the change of the potentiostatic current with time (PCT) experiments. The morphology of the surfaces of Ti and Ti-Zr after being corroded in SBF for 72 were investigated by a scanning electron microscope (SEM) and the analysis for the layer formed on that surface was collected via energy dispersive X-ray (EDX). Results depicted that the 15% Zr present within Ti decreases the corrosion via increasing Ti corrosion resistance and minimizing its measured corrosion rate. PCP data proved that the addition of Zr reduced all anodic, cathodic and corrosion currents. EIS results confirmed that Zr has a positive impact on the reduction of corrosion resistance. PCT, SEM, and EDX examinations displayed that both Ti and Ti-Zr alloy don’t show pitting corrosion even after 72 h exposure to SBF.


Crystals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1231
Author(s):  
Saud M. Almotairy ◽  
El-Sayed M. Sherif ◽  
Nabeel H. Alharthi ◽  
Hany S. Abdo ◽  
Hamad F. Alharbi ◽  
...  

In this work, the fabrication of three Al-2wt.% SiC nanocomposites processed by novel milling route was carried out. The beneficial influence of milling route on the corrosion passivation of the new fabricated composites was investigated. The cyclic polarization measurements have proved that increasing the time of ball milling highly reduced the corrosion of Al-SiC nanocomposite via reducing obtained corrosion current and so increasing the corrosion resistance. These results were affirmed by the electrochemical impedance spectroscopy experiments. The pitting corrosion of the manufactured composites was also reported, and its intensity decreased with the increase of ball milling time. The electrochemical experiments were also performed after expanding the exposure time in the chloride solution to 24 and 48. It was found that both the uniform and pitting corrosion decrease with prolonging the time. The study was complemented by examining the surface morphology and the elemental analyses for the different composites by using surface analyses techniques.


2021 ◽  
Vol 25 (Special) ◽  
pp. 2-39-2-48
Author(s):  
Saraa M. Mohammed ◽  
◽  
Sahib M. Mahdi ◽  

The corrosion behavior of both AA 2024 and AA 6061 aluminum alloys in 0.5M HCl before and after solution treatment at room temperature (25 oC) was investigated in this paper to know the effect of the solution heat treatment on the corrᴏsion behavior of both 2024 and 606 aluminum alloys. Using the cyclic polarization test, the corrosion resistance of AA 2024 aircraft aluminum alloy decreases after solution treatment at 495 oC for 2hr from (9.490×10-3 mm/y) to (1.309×10-3 mm/y), while the corrosion resistance of AA6061 aircraft aluminum alloy decreases after solution treatment at 530 oC for 2hr from (886.3× 10-3 mm/y) to (1.270×10-3 mm/y). Pitting corrosion was the prevalent type of corrosion for both alloys.


2021 ◽  
Vol 10 (6) ◽  
pp. e40610615861
Author(s):  
Ana Elisa Vilicev Italiano ◽  
Daniela Vieira Amantéa ◽  
Fernando Santos da Silva ◽  
Leandro Fernandes ◽  
Márcio Luiz dos Santos ◽  
...  

The objective of the present study was to evaluate the corrosion resistance of the experimental alloy Ti-35Nb-7Zr-5Ta, modified by laser beam, in a physiological solution of 0.9% NaCl. This evaluation was carried out by open circuit potential analysis (EOCP), potentiodynamic polarization curves and cyclic polarization curves. The open circuit potential curves show the specimen irradiated by laser beam at 35 Hz presented a more stable and corrosion resistant surface. It was observed in the polarization curves, low current densities in the order of nA /cm2, for all specimen indicating an expected passive behavior for the investigated alloy. The cyclic polarization curves show that for specimen treated with laser, the potential for repassivation (Er) is greater in relation to the potential for corrosion (Ecorr), which indicates greater resistance to corrosion of metal alloys when treated with laser.


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