Search

In order to study the corrosion dynamics of low carbon steel in neutral salt spray environment, the low carbon steel samples were carried out neutral salt spray corrosion test (SST). The corrosive behavior of low carbon steel was examined by scan electron microscopy, electrochemical impedance spectra, and potentiodynamic polarization, and the salt spray corrosion dynamics laws of low carbon steel were discussed. SST results showed that as the corrosion progresses, the rust layers will become dense, forming a "scab" structure, and forming an occluded corrosion zone with the substrate, resulting in increased corrosion rate. The newly generated inner rust layers were loose and expanded outward, caused the "scab" structure to peel off, and this has a certain periodicity. After corrosion, the surface of the substrate is pit-shaped, which uniformity is poor. Electrochemical tests showed that the corrosion process of low carbon steel in salt spray environment was mainly controlled by cathode diffusion, and the corrosion rate was relatively stable. [ABSTRACT FROM AUTHOR]

The effect of temperature and UV irradiation on the corrosion behavior of 304 stainless steel exposed to a simulated marine atmosphere was studied. The corroded samples were analyzed in detail through potentiodynamic polarization, in situ electrochemical impedance spectroscopy, Mott–Schottky measurements, scanning electron microscopy, and X‐ray photoelectron spectroscopy. The results showed that the corrosion rate of 304 SS was significantly inhibited by UV irradiation, and the inhibition effect increased at a higher temperature. The UV irradiation not only changed the corrosion products morphologies formed on the 304 SS surface but also the relative content of the corrosion products was changed. In particular, UV irradiation can promote the formation of Cr2O3 in corrosion products, especially at a higher temperature, thus improving the corrosion resistance of 304 SS. [ABSTRACT FROM AUTHOR]

In this paper, pulsed arc ion plating was applied for preparing Ti–Al–N coatings. The effects of different process parameters on the structure and corrosion resistance properties of Ti–Al–N coating were studied by changing the temperature. The microstructures, morphology features and the corrosion resistance of the different temperatures of Ti–Al–N coating were investigated to simulate the corrosion conditions of seawater. All the samples (prepared at 3 7 0 ∘ C, 3 7 5 ∘ C, 3 8 0 ∘ C and 3 8 5 ∘ C) were measured in 3.5 wt.% NaCl solution at 2 5 ∘ C and characterized by potentiodynamic polarization curves, scanning electron microscopy (SEM) combined with analyzed by X-ray diffraction (XRD). The corrosion resistance of carbon steel was improved by the coating modification. The results showed that the sample prepared at 3 8 0 ∘ C possesses excellent corrosion resistance where corrosion current density can only reach to 11.176 μ A/cm2, Meanwhile, SEM images also revealed that the microstructure of the sample is much smoother and nearly no defects can be observed. [ABSTRACT FROM AUTHOR]

This paper aims to determine the different sources of hydrogen that cause hydrogen embrittlement in ferrous materials. The 316L stainless steel was selected as the research object, and subjected to immersion and electrochemical tests in 1.0M HCl solution. The hardness and tensile strength of the test samples were measured before and after hydrogen embrittlement. The hydrogen, which exists in the form of hydrides, was detected through Xray diffractometry (XRD), while the fracture profile and microstructure of the samples were observed through optical microscopy and scanning electron microscopy (SEM), respectively. The results show that the hydrogen ions diffused into the surface of the steel, forming iron hydrides. In this way, the hardness of the steel was enhanced, and brittle failure occurred under tensile load; the amount of hydrides and the probability of hydrogen embrittlement increase with the immersion time in the acid solution; the sample immersed in 1.0M HCl for one day presented the most prominent hydrogen embrittlement, i.e. the highest hardness and lowest ductility. The research results provide insights into the occurrence of hydrogen embrittlement in ferrous materials. [ABSTRACT FROM AUTHOR]

In this study, the effects of WC nano-particles amount and surface roughness on corrosion behavior of magnesium metal matrix nano-composites in 3.5% NaCl solution are examined with the help of electrochemical test. Varying wt% of WC nano-particles (0.5, 1, 1.5 and 2) are used to fabricate metal matrix nano-composites through ultrasonic vibration assisted stir casting method. Basic characterizations of fabricated composites are performed by using scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDAX). SEM images show that nano-particles are well distributed throughout the magnesium matrix while EDAX results confirm the presence of WC particles in nano-composites. Micro-hardness result shows increasing trend with increasing weight percentage of WC. Mg nano-composite containing 0.5 wt% WC nano-particles is found to be the most corrosion resistive one followed by base alloy, Mg-2 wt%WC, Mg-1.5 wt%WC and Mg-1 wt%WC. Additionally, corrosion behavior of Mg-2WC with different surface quality is examined and it is observed that sample with lowest surface roughness shows better corrosion resistance. In the end, corrosion mechanisms are assessed with the help of SEM and EDAX study of corroded surfaces. [ABSTRACT FROM AUTHOR]

The corrosion behaviors of uncoated, enamel-coated, and epoxy-coated steel samples were evaluated in 3.5 wt.% NaCl solution with open-circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization tests. Two types of enamel (powder and slurry) were coated on steel samples in electrostatic and wet spraying processes, respectively. Twelve 25 mm × 25 mm steel samples were cut from an API 5L X65 pipe of 323.850 mm in outer diameter and 9.525 mm in wall thickness. They were divided into four groups of three identical samples. Each group represents one of the four conditions: uncoated, powder enamel-coated, slurry enamel-coated and epoxy-coated. Scanning electron microscopy images revealed that the powder and slurry enamel coatings were approximately 180 and 235 µm thick, respectively. The powder enamel coating has fewer but larger isolated pores than the slurry enamel coating. Electrochemical tests consistently indicated that the powder and slurry enamel coatings provided slightly better and worse corrosion protection to the coated steel samples, respectively, than the epoxy coating. The charge transfer resistances of all the coated samples are approximately 108 times larger than that of the uncoated samples. All the coated samples were unlikely corroded within 2 h of immersion. [ABSTRACT FROM AUTHOR]

Bismuth oxide thin films (250 nm) were deposited via unbalanced DC magnetron sputtering on Ti-6Al:4V, and common glass substrates. After being deposited, the films were heated (annealed) for 1 h between 473 and 1073 K in steps of 100 K. The morphology was characterized via scanning electron microscopy (SEM), the micro-structure was analyzed through x-ray diffraction (XRD), and the electrochemical behavior was analyzed with the potentiodynamic polarization test. Additionally, a proton-induced X-ray emission (PIXE) test was done on one of the samples in order to check the chemical distribution of the elements in the surface. The SEM and XRD analyses showed that the post-annealing process affects both the morphology and the structure of the films for all the samples. Finally, the electrochemical tests showed that films grown at 773 K have the highest degree of corrosion resistance. [ABSTRACT FROM AUTHOR]

The electrochemical characteristics of Ti-6Al-4V after plasma electrolytic oxidation (PEO) in solutions containing Ca, P, and Zn ions were studied using various experimental techniques. A Ti-6Al-4V ELI disk was used as a substrate for plasma electrolytic oxidation. A pulsed DC power supply was used to apply a potential of 280 V in the electrolyte for 3 min. To analyze the electrochemical properties of the PEO film as a function of the Zn content, potentiodynamic and AC impedance tests were carried out with a potentiostat (Model 2273, EG&G Co., USA) using a 0.9% NaCl solution. To examine the bioactivity, the PEO films formed on the specimens and the untreated Ti-6Al-4V specimens were immersed in a simulated body fluid (SBF) for 12 h. The PEO-treated and SBF-immersed surfaces were observed by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and attenuated total reflectance Fourier transform infrared spectroscopy. The number of pores in the PEO films increased, whereas the pore size decreased slightly, as the Zn ion concentration increased. The corrosion potential of the PEO-treated films decreased, while the corrosion current density increased slightly, as the Zn content increased. As shown by the Nyquist plots, the semicircular region in the profile of the Ti-6Al-4V specimens increased compared to that of the other specimens. The films obtained after PEO treatment in the solution containing Zn showed Warburg impedance characteristics. Bone-like apatite was well-formed in specimens of PEO films treated in solutions containing Zn ions at concentrations of 0, 5, and 10 mM%. However, formation of the bone-like apatite decreased in specimens of the PEO films treated in a solution containing Zn ions at a concentration of 20 mM%. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the study was to evaluate corrosion resistance of Wirobond C® alloy after chemical passivation treatment. Methods: The alloy surface undergone chemical passivation treatment in four different media. Corrosion studies were carried out by means of electrochemical methods in saline solution. Corrosion effects were determined using SEM. Results: The greatest increase in the alloy polarization resistance was observed for passive layer produced in Na2SO4 solution with graphite. The same layer caused the highest increase in corrosion current. Generally speaking, the alloy passivation in Na2SO4 solution with graphite caused a substantial improvement of the corrosion resistance. The sample after passivation in Na2SO4 solution without graphite, contrary to others, lost its protective properties along with successive anodic polarization cycles. The alloy passivation in Na3PO4 solution with graphite was the only one that caused a decrease in the alloy corrosion properties. The SEM studies of all samples after chemical passivation revealed no pit corrosion - in contrast to the sample without any modification. Conclusions: Every successive polarization cycle in anodic direction of pure Wirobond C® alloy enhances corrosion resistance shifting corrosion potential in the positive direction and decreasing corrosion current value. The chemical passivation in solutions with low pH values decreases susceptibility to electrochemical corrosion of Co-Cr dental alloy. The best protection against corrosion was obtained after chemical passivation of Wirobond C® in Na2SO4 solution with graphite. Passivation with Na2SO4 in solution of high pH does not cause an increase in corrosion resistance of WIROBOND C. Passivation process increases alloy resistance to pit corrosion. [ABSTRACT FROM AUTHOR]

Of the alloying additions to magnesium to date, Ta has not been widely studied. Herein, the effect of Ta on the microstructure and corrosion of Mg-6.7Y-2.5Zn was investigated using optical microscopy, scanning electron microscopy, electrochemical measurements and mass loss. The results showed that the addition of Ta can effectively improve the corrosion resistance of Mg-6.7Y-2.5Zn alloy and change the local corrosion to uniform corrosion. The addition of Ta can rapidly form a dense corrosion product film on Mg-6.7Y-2.5Zn alloy, thus effectively preventing the later corrosion. • Trace Ta in Mg-6.7Y-2.5Zn alloy alters phase distribution shape, enhances corrosion resistance. • The corrosion properties of the samples were evaluated by weight loss method and electrochemical test. • The addition of Ta changes the local corrosion of Mg-6.7Y-2.5Zn alloy into uniform corrosion. • The addition of Ta improved the quality of the corrosion product film. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we try to employ a method of a combination of epoxy functionalized silica sol (ESol) and thiourea (TUA) to obtain a coating of excellent anticorrosion effect on copper. In order to compare the anticorrosion ability of the ESol+TUA coating with other coatings, the samples of ESol and ESol with diethylenetriamine (ESol+DETA) coatings have also been prepared. We use a variety of corresponding methods to study the properties of ESol with and without adding DETA and TUA. Aqueous contact angle analysis is used to evaluate the wetting properties of these sol–gel coatings. Scanning electron microscopy (SEM) is used to observe the surface morphology of these coatings and their cross sections. The anticorrosion ability of these coatings is evaluated by electrochemical methods and salt spray tests. The results show that ESol+TUA coating has the best anticorrosion ability. This is because adding TUA improves the physical barrier effect due to the denser coating compared to the regular ESol coating; in addition, it improves the adhesion between the coating and copper surface. [Copyright &y& Elsevier]

Abstract: In this paper, the corrosion behavior of NiTi thin films implanted with argon, carbon and nitrogen ions was investigated by potentiodynamic scanning (PDS) and electrochemical impedance spectroscopy (EIS) methods. PDS results showed that the icorr was decreased after implantation with carbon and nitrogen and increased with argon ions. EIS measurements also indicated that the corrosion resistance (Rp) of the films implanted with carbon and nitrogen was increased and with argon implantation decreased. Scanning electron microscopy (SEM) images showed a lesser amount of corrosion defects in nitrogen and carbon implanted thin films and more amounts in argon implanted and unimplanted film surfaces. The cracks are also observed on argon implanted surface. [Copyright &y& Elsevier]

Abstract: The use of antimicrobial corrosion inhibitor is increasingly being curtailed by recent corrosion restrictions. This paper represents the results of the study of new biocide, antimicrobial corrosion inhibitor named 8-hydroxy-N′-(2-(quinolin-8-yloxy)acetyl)quinoline-5-sulfonohydrazide (HQS) was used to inhibit corrosion causing sulphate reducing bacteria (SRB). The effects of the inhibitor on mild steel dissolution in salty water environment were studied through weight loss measurements, electrochemical and microorganism tests. The results obtained from this study show that, the new inhibitor can decrease corrosion and microbial growth under the conditions tested. The mass loss for the protected mild steel coupons shows lower corrosion rate compared to the unprotected once. Cyclic polarization test reveals that, the biocide minimizes the pitting area (hysteresis). The nature of protective film formed on mild steel was studied by scanning electron microscopy (SEM). SEM images revealed that, the corrosion inhibition by the HQS on the mild steel surface significantly improved in the presence of biocide. [Copyright &y& Elsevier]

Structured Abstract Authors – Luft S, Keilig L, Jäger A, Bourauel C Objective – The number of bracket systems for orthodontic therapy increases significantly. One major concern of newly developed orthodontic devices is aspects of corrosion and biocompatibility. Material and Methods – In this study, nine bracket systems made of different material and from various design principles were tested with respect to their corrosion behavior. Electrochemical and static immersion tests with subsequent measurement of nickel ion release were performed. In addition surface alterations of the brackets after corrosion were documented by scanning electron microscopy. Studies of corrosion behavior were performed according to the DIN/ISO standard 10271 for corrosion testing of dental materials. Results – All systems showed traces of corrosion after electrochemical testing. However, after static immersion testing only minor corrosion defects could be documented and the measured nickel ion release was far below critical limits. Conclusions – All tested systems seem to be biocompatible and applicable for orthodontic therapy. The measured nickel values are far below the daily dietary intake level. A static immersion test combined with the nickel ion release measurement seems to be more relevant for the determination of biocompatibility than the electrochemical testing. [ABSTRACT FROM AUTHOR]

In this study, graphene/silver nanowire (Gr/AgNW)-based, Fe-C coated long period fiber gratings (LPFG) sensors were tested up to 72 hours in 3.5 w.t% NaCl solution for corrosion-induced mass loss measurement under four strain levels: 0, 500, 1000 and 1500 µε. The crack and interfacial bonding behaviors of laminate Fe-C and Gr/AgNW layer structures were characterized using Scanning Electron Microscopy (SEM) and electrical resistance measurement. Both optical transmission spectra and electrical impedance spectroscopy (EIS) data were simultaneously measured from each sensor. Under increasing strains, transverse cracks appeared first and were followed by longitudinal cracks on the laminate layer structures. The spacing of transverse cracks and the length of longitudinal cracks were determined by the bond strength at the weak Fe-C and Gr/AgNW interface. During corrosion tests, the shift in resonant wavelength of the Fe-C coated LPFG sensors resulted from the effects of the Fe-C layer thinning and the NaCl solution penetration through cracks on the evanescent field surrounding the LPFG sensors. Compared with the zero-strained sensor, the strain-induced cracks on the laminate layer structures initially increased and then decreased the shift in resonant wavelength in two main stages of the Fe-C corrosion process. In each corrosion stage, the Fe-C mass loss was linearly related to the shift in resonant wavelength under zero strain and with the applied strain taken into account in general cases. The general correlation equation was validated at 700 and 1200 µε to a maximum error of 2.5% in comparison with 46.5% from the zero-strain correlation equation. [ABSTRACT FROM AUTHOR]