Use of Scanning Vibrating Electrode Technique to Localized Corrosion Evaluation

2015 ◽  
Vol 228 ◽  
pp. 353-368 ◽  
Author(s):  
Bożena Łosiewicz ◽  
Magdalena Popczyk ◽  
Magdalena Szklarska ◽  
Agnieszka Smołka ◽  
Patrycja Osak ◽  
...  
Keyword(s):  
Current Density ◽  
Potential Gradient ◽  
Localized Corrosion ◽  
Review Of The Literature ◽  
Testing Methods ◽  
Electrochemical Testing ◽  
Local Element ◽  
Corrosion Evaluation ◽  
Alloy Steels ◽  
Electrode Technique

This work presents the basic theory and the usability of the scanning vibrating electrode technique (SVET), especially in the field of corrosion. At present, SVET is to be considered as one of the latest electrochemical testing methods. The essence of determining the current density resulting from corrosion is limited to the measurement of the potential gradient between the two points on the surface of the metal and over it, within the electric field of a local element. SVET has been used to study local, galvanic and intercrystalline corrosion. It is particularly useful in studying the corrosion of alloy steels and welding agents. This paper presents a review of the literature on the newest research in this field.

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.

Measuring surface potential components necessary for transmembrane current computation using microfabricated arrays

2005 ◽  
Vol 289 (6) ◽  
pp. H2468-H2477 ◽  
Author(s):  
J. James Wiley ◽  
Raymond E. Ideker ◽  
William M. Smith ◽  
Andrew E. Pollard
Keyword(s):  
Spatial Resolution ◽  
Current Density ◽  
Potential Gradient ◽  
Electrode Spacing ◽  
Back Side ◽  
Transmembrane Current ◽  
Fine Wire ◽  
Microfabricated Arrays ◽  
Potential Gradients ◽  
Unipolar Electrograms

This study was designed to test the feasibility of using microfabricated electrodes to record surface potentials with sufficiently fine spatial resolution to measure the potential gradients necessary for improved computation of transmembrane current density. To assess that feasibility, we recorded unipolar electrograms from perfused rabbit right ventricular free wall epicardium ( n = 6) using electrode arrays that included 25-μm sensors fabricated onto a flexible substrate with 75-μm interelectrode spacing. Electrode spacing was therefore on the size scale of an individual myocyte. Signal conditioning adjacent to the sensors to control lead noise was achieved by routing traces from the electrodes to the back side of the substrate where buffer amplifiers were located. For comparison, recordings were also made using arrays built from chloridized silver wire electrodes of either 50-μm (fine wire) or 250-μm (coarse wire) diameters. Electrode separations were necessarily wider than with microfabricated arrays. Comparable signal-to-noise ratios (SNRs) of 21.2 ± 2.2, 32.5 ± 4.1, and 22.9 ± 0.7 for electrograms recorded using microfabricated sensors ( n = 78), fine wires ( n = 78), and coarse wires ( n = 78), respectively, were found. High SNRs were maintained in bipolar electrograms assembled using spatial combinations of the unipolar electrograms necessary for the potential gradient measurements and in second-difference electrograms assembled using spatial combinations of the bipolar electrograms necessary for surface Laplacian (SL) measurements. Simulations incorporating a bidomain representation of tissue structure and a two-dimensional network of guinea pig myocytes prescribed following the Luo and Rudy dynamic membrane equations were completed using 12.5-μm spatial resolution to assess contributions of electrode spacing to the potential gradient and SL measurements. In those simulations, increases in electrode separation from 12.5 to 75.0, 237.5, and 875.0 μm, which were separations comparable to the finest available with our microfabricated, fine wire, and coarse wire arrays, led to 10%, 42%, and 81% reductions in maximum potential gradients and 33%, 76%, and 96% reductions in peak-to-peak SLs. Maintenance of comparable SNRs for source electrograms was therefore important because microfabrication provides a highly attractive methods to achieve spatial resolutions necessary for improved computation of transmembrane current density.

Corrosion Evaluation of Ferritic Stainless Steels for Automotive Exhaust Applications

CORROSION ◽  
10.5006/3319 ◽  
2019 ◽  
Vol 75 (11) ◽  
pp. 1276-1280
Author(s):  
Y. Emun ◽  
H.S. Zurob ◽  
J.R. Kish
Keyword(s):  
Stainless Steels ◽  
Localized Corrosion ◽  
Bench Mark ◽  
Neutral Salt ◽  
Automotive Exhaust ◽  
Metallographic Examination ◽  
Ferritic Stainless Steels ◽  
Corrosion Evaluation ◽  
Corrosion Susceptibility ◽  
Salt Fog

This study compares the localized (exterior) corrosion susceptibility of chromized steel to bench-mark ferritic stainless steels for automotive exhaust applications. Continuous near-neutral salt fog exposure (ASTM B117) was used for this purpose. Corrosion susceptibility was determined using mass loss measurements coupled with a post exposure metallographic examination. Complementary potentiodynamic polarization measurements were made in the bulk salt solution to help interpret the relative performance. The elevated Cr content provided by the chromizing surface treatment provides comparable corrosion resistance to the more highly alloyed ferritic stainless steels studied. The major factor affecting localized corrosion susceptibility is the formation of rust deposits, which act as effective pit-like corrosion initiation sites.

Using Additive Manufacturing for Making Light Water Reactor Components

2019 ◽  
Author(s):  
Raul B. Rebak ◽  
Xiaoyuan Lou
Keyword(s):  
Additive Manufacturing ◽  
Failure Modes ◽  
Light Water Reactor ◽  
Localized Corrosion ◽  
General Corrosion ◽  
Light Water ◽  
Water Reactor ◽  
Electrochemical Testing ◽  
Deployment Time ◽  
High Degree

Abstract Making light water reactor (LWR) components using additive manufacturing (AM) provides a high degree of design freedom to create complex near net shape geometries, with significant reduction in the deployment time. Since most of the current AM research focus on the refining of the fabrication variables, little information exists on the actual corrosion behavior (including general corrosion, localized corrosion and environmentally assisted cracking - EAC) of AM components. The most frequent operational material failure modes in LWR is EAC and debris fretting of fuel rods, therefore the objective of this work was to evaluate the environmental performance of AM type 316L SS in relation to the traditionally melted and forged wrought material. Stress corrosion cracking results show similar behavior between AM and wrought 316L SS in high temperature water. Ambient temperature electrochemical testing showed that the AM 316L SS was slightly more resistant to localized corrosion than the traditional wrought material and that AM material did not suffer sensitization during fabrication or heat treatment processes.

Measuring the atmospheric corrosion of Q235B and T91 steels using gray value, wavelet analysis and fuzzy Kolmogorov–Sinai entropy

2019 ◽  
Vol 66 (5) ◽  
pp. 621-630 ◽  
Author(s):  
Li-Xiang Wang ◽  
Da-Hai Xia ◽  
Shi-Zhe Song ◽  
Yashar Behnamian ◽  
Likun Xu
Keyword(s):  
Image Analysis ◽  
Wavelet Analysis ◽  
Atmospheric Corrosion ◽  
Localized Corrosion ◽  
Uniform Corrosion ◽  
Metallic Materials ◽  
Atmospheric Conditions ◽  
Content Type ◽  
Corrosion Evaluation ◽  
One Year

Purpose This paper aims to quantify atmospheric corrosion by image analyses. The corrosion extent, form and distribution of corrosion product on Q235B and T91 steels exposed to a Zhoushan marine atmosphere over one year are characterized by image analysis. Design/methodology/approach Image analysis of corrosion images were achieved using the gray value, wavelet analysis and fuzzy Kolmogorov–Sinai (K–S) entropy. Findings As corrosion becomes extensive, the gray value of corrosion images decreases, and the energy value of nine subimages after wavelength decomposition decreases. Fuzzy K–S entropy increases as localized corrosion propagates but decreases as uniform corrosion spreads. Originality/value The methods proposed in this work open a new way for fast corrosion evaluation of metallic materials exposed to atmospheric conditions.

Current Density Contour Map of TiNi Shape Memory Alloy in Simulated Physiological Solutions

2007 ◽  
Vol 342-343 ◽  
pp. 573-576
Author(s):  
Woon Suk Hwang ◽  
Seung Chan Na ◽  
Jeong Ja Lee
Keyword(s):  
Sodium Chloride ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Current Density ◽  
Localized Corrosion ◽  
Tini Alloy ◽  
Contour Map ◽  
Chloride Solutions ◽  
Sodium Chloride Solutions ◽  
Density Contour

In order to investigate the corrosion behavior of TiNi shape memory alloy, especially electrochemical behavior of pitting and crevice corrosion in a human body, current density contour(CDC) map of TiNi alloy was constructed by potentiodynamic polarization technique in simulated physiological sodium chloride solutions of pH ranging from 1 to 13 at 37oC. Morphology of pits and corrosion products in sodium chloride solutions of various pH were analyzed by SEM and EDX, and susceptibility and mechanism of localized corrosion were also discussed.

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.

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