Localized Corrosion of Binary Mg-Nd Alloys in Chloride-Containing Electrolyte Using a Scanning Vibrating Electrode Technique

CORROSION ◽  
2012 ◽  
Vol 68 (6) ◽  
pp. 489-498 ◽  
Author(s):  
G. Williams ◽  
K. Gusieva ◽  
N. Birbilis
Keyword(s):  
Localized Corrosion ◽  
Radial Expansion ◽  
Alloying Additions ◽  
Corrosion Rates ◽  
Surface Breakdown ◽  
Density Values ◽  
Intact Surface ◽  
Mean Current ◽  
Electrode Technique

The influence of neodymium (Nd) alloying additions in the 0.47 wt% to 3.53 wt% range on the localized corrosion behavior of Mg, when freely corroding in aqueous sodium chloride (NaCl) electrolyte, is investigated using an in situ scanning vibrating electrode technique (SVET). For all samples, the point of surface breakdown is an intense focal anode that expands radially with respect to time, revealing a cathodically activated interior, which is galvanically coupled with the local anode at the perimeter. However, for Nd compositions of ≤0.74%, radial expansion ceases within ca. 2 h of initiation, whereupon dark filiform-like corrosion features are observed, which traverse over the exposed Mg surface. For Nd additions of ≥1.25%, the radial expansion continues with time up to a point where the entire intact surface becomes consumed. The intensity of the local anode ring of circular corroded regions is seen to increase as more cathodically activated corroded surface becomes exposed. Mean current density values measured within these corroded areas increase progressively with Nd content, leading to a progressive rise in localized corrosion rates. The cathodic activation of corroded regions is proposed to derive from an enrichment of noble, Nd-rich intermetallic grains caused as the alpha-Mg phase becomes attacked at local anode sites.

Effect of pH on the Grain Size Dependence of Magnesium Corrosion

CORROSION ◽  
2012 ◽  
Vol 68 (6) ◽  
pp. 507-517 ◽  
Author(s):  
K. D. Ralston ◽  
G. Williams ◽  
N. Birbilis
Keyword(s):  
Grain Size ◽  
Corrosion Rate ◽  
Anodic Polarization ◽  
Localized Corrosion ◽  
Anodic Reaction ◽  
Left Behind ◽  
Kinetics Of ◽  
Electrode Technique

Prior works show that grain size can play a role in the corrosion of a metal; however, such works are nominally executed in a single electrolyte/environment at a single pH. In this work, the anodic and cathodic reaction kinetics of pure Mg specimens with grain sizes ranging from approximately 8 μm to 590 μm were compared as a function of pH in 0.1 mol dm−3 sodium chloride (NaCl) electrolytes using anodic polarization experiments and an in situ scanning vibrating electrode technique (SVET). Anodic polarization experiments showed that grain size is important in determining overall electrochemical response, but the environment dictates the form of the grain size vs. corrosion rate relationship (i.e., pH is the overall controlling factor). Consequently, the role of grain size upon corrosion cannot be fully assessed unless a variation in environment is simultaneously studied. For example, the anodic reaction, which dictates active corrosion, also dictates passivation, so the corrosion rate vs. grain size relationship has been shown to “flip” depending on pH. Further, SVET analysis of unpolarized Mg immersed in 0.1 mol dm−3 NaCl electrolyte at neutral pH showed that breakdown of passivity of cast Mg occurred after ~1 h immersion, giving filiform-like corrosion tracks. The front edges of these corrosion features were revealed as intense local anodes, while the remainder of the dark-corroded Mg surface, left behind as the anodes traversed the surface, became cathodically activated. In contrast, grain-refined Mg samples were significantly less susceptible to localized corrosion, and breakdown was not observed for immersion periods of up to 24 h.

Measurement of localized corrosion rates at inclusion particles in AA7075 by in situ three dimensional (3D) X-ray synchrotron tomography

2016 ◽  
Vol 104 ◽  
pp. 330-335 ◽  
Author(s):  
Sudhanshu S. Singh ◽  
Jason J. Williams ◽  
Tyler J. Stannard ◽  
Xianghui Xiao ◽  
Francesco De Carlo ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Localized Corrosion ◽  
X Ray ◽  
Corrosion Rates ◽  
Synchrotron Tomography

Mathematical Model Investigation of Far-Field Transport of Ocean-Dumped Sewage Sludge Related to Remote Sensing

1982 ◽  
Vol 14 (3) ◽  
pp. 33-39
Author(s):  
C Y Kuo
Keyword(s):  
New York ◽  
Sewage Sludge ◽  
Laboratory Data ◽  
Three Dimensional ◽  
Approximate Model ◽  
Transport Processes ◽  
Far Field ◽  
New York Bight ◽  
Mean Current

An existing, three-dimensional, Eulerian-Lagrangian finite-difference model was modified and used to examine the far-field transport processes of dumped sewage sludge in the New York Bight. Both in situ and laboratory data were utilized in an attempt to approximate model inputs such as mean current speed, vertical and horizontal diffusion coefficients, particle size distributions, and specific gravities. Concentrations of the sludge near the sea surface predicted from the computer model were compared qualitatively with those remotely sensed.

scholarly journals Designing Advanced Biomedical Biodegradable Mg Alloys: A Review

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 85
Author(s):  
Murtatha M. Jamel ◽  
Mostafa M. Jamel ◽  
Hugo F. Lopez
Keyword(s):  
Mechanical Properties ◽  
Biomedical Applications ◽  
Hydrogen Generation ◽  
Mg Alloys ◽  
Living Tissue ◽  
Effective Factors ◽  
Alloying Additions ◽  
Mechanical Integrity ◽  
Corrosion Rates ◽  
Mechanical Properties And Corrosion

The increased demand for alloys that can serve as implantation devices with outstanding bio-properties has led to the development of numerous biomedical Mg-based alloys. These alloys have been extensively investigated for their performance in living tissue with mixed results. Hence, there are still major concerns regarding the use of magnesium alloys for such applications. Among the issues raised are elevated corrosion rates, hydrogen generation, and the maintenance of mechanical integrity for designated healing times. In addition, toxicity can arise from the addition of alloying elements that are intended to improve the mechanical integrity and corrosion resistance of Mg alloys. The current work reviews the recent advances in the development of Mg alloys for applications as bio-absorbable materials in living organic environments. In particular, it attempts to develop a roadmap of effective factors that can be utilized when designing Mg alloys. Among the factors reviewed are the effects of alloying additions and processing methods on the exhibited mechanical properties and corrosion rates in simulated bio-fluids used in biomedical applications.

scholarly journals A Study into the Localized Corrosion of Magnesium Alloy Magnox Al-80

CORROSION ◽  
10.5006/3574 ◽  
2020 ◽  
Author(s):  
Ronald Clark ◽  
James Humpage ◽  
Robert Burrows ◽  
Hugh Godfrey ◽  
Mustufa Sagir ◽  
...  
Keyword(s):  
Passive Film ◽  
Ph Dependence ◽  
Chloride Concentration ◽  
Ion Concentration ◽  
Localized Corrosion ◽  
High Concentration ◽  
Transfer Resistance ◽  
High Ph ◽  
Intact Surface ◽  
Chloride Concentrations

Magnesium (Mg) non-oxidizing alloy, known as Magnox, was historically used as a fuel cladding material for the first-generation of carbon dioxide (CO<sub>2</sub>) gas-cooled nuclear reactors in the UK. Waste Magnox is currently stored in cooling ponds, pending final disposal. The corrosion resistance of Mg and its alloys is relatively poor, compared to modern cladding materials such as zirconium (Zr) alloys, so it is important to have a knowledge of the chloride concentration/pH dependence on breakdown and localized corrosion characteristics prior to waste retrievals taking place. Our results show that Magnox exhibits passivity in high pH solutions, with charge transfer resistance and passive film thicknesses showing an increase with immersion time. When chloride is added to the system the higher pH maintains Magnox passivity, as shown through a combination of potentiodynamic and time-lapse/post corrosion imaging experiments. Potentiodynamic polarization of Magnox reveals a -229 mV<sup>-decade</sup> linear dependence of breakdown potential with chloride ion concentration. The use of the scanning vibrating electrode technique (SVET) enabled the localized corrosion characteristics to be followed. At high pH where Magnox is passive, at low chloride concentrations, the anodes which form predominantly couple to the visually intact surface in the vicinity of the anode. The high pH however means that visually intact Magnox in the vicinity of the anode is less prone to breakdown, restricting anode propagation such that they remain largely static. In high chloride concentrations the higher conductivity means that the anode and cathode can couple over greater distances and so propagation along the surface can occur at a much faster rate, with the visually intact surface acting as a distributed cathode. In addition, the chloride anion itself, when present at high concentration will play a role in rapid passive film dissolution, enabling rapid anode propagation.

scholarly journals In-Situ Monitoring and Analysis of the Pitting Corrosion of Carbon Steel by Acoustic Emission

2019 ◽  
Vol 9 (4) ◽  
pp. 706 ◽  
Author(s):  
Junlei Tang ◽  
Junyang Li ◽  
Hu Wang ◽  
Yingying Wang ◽  
Geng Chen
Keyword(s):  
Acoustic Emission ◽  
Carbon Steel ◽  
Pitting Corrosion ◽  
Optical Microscope ◽  
Open Circuit ◽  
In Situ Monitoring ◽  
Localized Corrosion ◽  
Uniform Corrosion ◽  
Corrosion Morphology

The acoustic emission (AE) technique was applied to monitor the pitting corrosion of carbon steel in NaHCO3 + NaCl solutions. The open circuit potential (OCP) measurement and corrosion morphology in-situ capturing using an optical microscope were conducted during AE monitoring. The corrosion micromorphology was characterized with a scanning electron microscope (SEM). The propagation behavior and AE features of natural pitting on carbon steel were investigated. After completion of the signal processing, including pre-treatment, shape preserving interpolation, and denoising, for raw AE waveforms, three types of AE signals were classified in the correlation diagrams of the new waveform parameters. Finally, a 2D pattern recognition method was established to calculate the similarity of different continuous AE graphics, which is quite effective to distinguish the localized corrosion from uniform corrosion.

In Situ Scanning Vibrating Electrode Technique for the Characterization of Interface Between Lithium Electrode and Electrolytes Containing Additives

1994 ◽  
Vol 141 (12) ◽  
pp. L159-L161 ◽  
Author(s):  
Masashi Ishikawa ◽  
Shinsuke Yoshitake ◽  
Masayuki Morita ◽  
Yoshiharu Matsuda
Keyword(s):  
Lithium Electrode ◽  
Electrode Technique
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