scholarly journals THE EFFECTS OF POLARIZATION UPON THE STEEL WIRE-NITRIC ACID MODEL OF NERVE ACTIVITY

1927 ◽  
Vol 11 (2) ◽  
pp. 159-174 ◽  
Author(s):  
George H. Bishop
Keyword(s):  
Nitric Acid ◽  
Protective Coatings ◽  
Steel Wire ◽  
Potential Drop ◽  
Electrochemical Protection ◽  
Total Potential ◽  
Oxidation Reduction ◽  
Refractory State ◽  
Passivation Potential ◽  
Potential Equilibrium

The active process in a short length of steel wire passivated by 65 per cent nitric acid has been observed under the influence of a polarizing current, and the form of the potential recorded by the cathode ray oscillograph. In the passive wire, 80 per cent of the total potential drop takes place at the anode, 20 per cent at the cathode. The change from active to passive states, as measured by the potential change, is very abrupt compared to the duration of activity and the potential curve at a point on the wire is probably almost rectangular. The duration of the refractory state is decreased at the anode and increased at the cathode, as in nerve. This fact is against the idea that reactivity after passivation results from a partial reduction of an oxide layer. Soft iron wire passivated by anodal polarization repassivates after activation in acid of a dilution that fails to passivate it initially. It soon becomes rhythmic with a very short refractory phase, and then reacts continuously. Such a wire exhibits a very sharp alternation between a dark brown oxide coat during activity, and a bright clean surface during passivation. A passive steel wire in nitric acid shows many of the characteristics of an inert electrode such as platinum, and it may be inferred that, superposed upon the primary passivation potential, there exists an electrode or oxidation-reduction potential equilibrium between the effects of the various constituents of the solution. It is suggested that the phenomena of nerve-like reactivity in this system may involve an alternation between two protective coatings of the steel wire. During activity, the surface becomes mechanically coated with a brown oxide. If this coating does not adhere, due to gas convection or to rapid solution of the oxide, passivation does not result. Under sufficiently intense oxidizing conditions, a second oxide coat may form in the interstices of the first, and cover the surface as the first coating dissolves off. This furnishes the electrochemical protection of passivation, which is followed by the gradual attainment of electrode equilibrium with the solution.

Current-voltage curves for ion-exchange membranes. Contributions to the total potential drop

1991 ◽  
Vol 61 ◽  
pp. 177-190 ◽  
Author(s):  
V.M. Aguilella ◽  
S. Mafe ◽  
J.A. Manzanares ◽  
J. Pellicer
Keyword(s):  
Ion Exchange ◽  
Potential Drop ◽  
Ion Exchange Membranes ◽  
Total Potential ◽  
Current Voltage

On the Passivity of Iron★

CORROSION ◽  
1955 ◽  
Vol 11 (7) ◽  
pp. 32-36 ◽  
Author(s):  
KARL FRIEDRICH BONHOEFFER
Keyword(s):  
Nitric Acid ◽  
Current Density ◽  
Nitrous Acid ◽  
Redox System ◽  
Equivalent Current ◽  
Passivation Current Density ◽  
Passivation Potential

Abstract Descriptions are given of the various phenomena associated with the passivation and reactivation of iron in concentrated nitric acid. Covered are apparent and true passivation potential, apparent and true passivation current density, passivity producing and passivity maintaining current density. Information is given also on equivalent current density in a redox system, the role of nitrous acid in passivation by concentrated nitric acid, the corrosion of passive iron, refractoriness toward activation, rhythms and activity waves.

scholarly journals Minimization of self-potential survey mis-ties acquired with multiple reference locations

Geophysics ◽  
2008 ◽  
Vol 73 (2) ◽  
pp. F71-F81 ◽  
Author(s):  
Burke J. Minsley ◽  
Darrell A. Coles ◽  
Yervant Vichabian ◽  
Frank Dale Morgan
Keyword(s):  
Potential Field ◽  
Measurement Errors ◽  
Computational Cost ◽  
Potential Drop ◽  
Iterative Solution ◽  
Data Set ◽  
Loop Closure ◽  
Total Potential ◽  
Self Potential ◽  
Unique Potential

Self-potential (SP) surveys often involve many interconnected lines of data along available roads or trails, with the ultimate goal of producing a unique map of electric potentials at each station relative to a single reference point. Multiple survey lines can be tied together by collecting data along intersecting transects and enforcing Kirchhoff’s voltage law, which requires that the total potential drop around any closed loop equals zero. In practice, however, there is often a nonzero loop-closure error caused by noisy data; traditional SP processing methods redistribute this error evenly over the measurements that form each loop. The task of distributing errors and tying lines together becomes nontrivial when many lines of data form multiple interconnected loops because the loop-closure errors are not independent, and a unique potential field cannot be determined by processing lines sequentially. We present a survey-consistent processing method that produces a unique potential field by minimizing the loop-closure errors over all lines of data simultaneously. When there are no interconnected survey loops, the method is equivalent to traditional processing schemes. The task of computing the potential field is posed as a linear inverse problem, which easily incorporates prior information about measurement errors and model constraints. We investigate the use of both [Formula: see text] and [Formula: see text] measures of data misfit, the latter requiring an iterative-solution method with increased computational cost. The [Formula: see text] method produces more reliable results when outliers are present in the data, and is similar to the [Formula: see text] result when only Gaussian noise is present. Two synthetic examples are used to illustrate this methodology, which is subsequently applied to a field data set collected as part of a geothermal exploration campaign in Nevis, West Indies.

THE ELECTROCHEMICAL MECHANISM OF SULFIDE SELF‐POTENTIALS

Geophysics ◽  
1960 ◽  
Vol 25 (1) ◽  
pp. 226-249 ◽  
Author(s):  
Motoaki Sato ◽  
Harold M. Mooney
Keyword(s):  
Water Table ◽  
Potential Drop ◽  
Reducing Agents ◽  
Oxidation Potential ◽  
Simultaneous Reduction ◽  
Oxidizing Agents ◽  
Ore Body ◽  
Oxidation Reduction ◽  
Ohmic Potential Drop ◽  
Different Depths

Self‐potentials associated with a sulfide ore body result from the ohmic potential drop within the country rocks. The electric current is produced by separate but simultaneous reduction of oxidizing agents near the surface and oxidation of reducing agents at depth. The ore does not participate directly in either reaction, but serves as a conductor to transfer the electrons from the reducing agents to the oxidizing agents. The possibility for the above reactions to occur depends upon differences in oxidation potential of ground waters at different depths. In the zone of weathering, the oxidation potential is controlled by the reduction mechanism of oxygen, and ranges in value from 0.2 to 0.7 volt (on the hydrogen scale). If the ore tends to oxidize at some lower potential, then the latter is the available one. In the zone beneath the water table, the potential is probably controlled by the oxidation‐reduction equilibria of iron‐rich minerals, and ranges in value from 0 to −0.3 volt. The available potential is independent of ore type. The maximum potential difference available to produce natural currents is estimated at: graphite 0.8, pyrite 0.7, covellite 0.6, chalcocite 0.5, galena 0.3 volt. Self‐potentials will be large if the ore body (1) is composed of minerals difficult to oxidize, (2) has low electrical resistance (physical continuity together with low resistivity), (3) extends vertically across the water table, and (4) exists close to the surface.

scholarly journals Divalent Ion-Specific Outcomes on Stern Layer Structure and Total Surface Potential at the Silica:Water Interface

2021 ◽  
Author(s):  
Emily Ma ◽  
Franz Geiger
Keyword(s):  
Layer Structure ◽  
Divalent Cations ◽  
Potential Drop ◽  
Fused Silica ◽  
Interfacial Structure ◽  
Nonlinear Susceptibility ◽  
Stern Layer ◽  
Phase Measurements ◽  
Total Potential ◽  
Interfacial Potential

The second-order nonlinear susceptibility, chi(2), in the Stern layer, and the total interfacial potential drop, Phi(0)tot, across the oxide:water interface are estimated from SHG amplitude and phase measurements for divalent cations (Mg2+, Ca2+, Sr2+, Ba2+) at the silica:water interface at pH 5.8 and various ionic strengths. We find that interfacial structure and total potential depend strongly on ion valency. We observe statistically significant differences between the experimentally determined chi(2) value for NaCl and that of the alkali earth series, but smaller differences between ions of the same valency in that series. These differences are particularly pronounced at intermediate salt concentrations, which we attribute to the influence of hydration structure in the Stern layer. Furthermore, we corroborate the differences by examining the effects of anion substitution (SO4 2- for Cl-). Finally, we identify that hysteresis in measuring the reversibility of ion adsorption and desorption at fused silica in forward and reverse titrations manifests itself both in Stern layer structure and in total interfacial potential for some of the salts, most notable CaCl2 and MgSO4, but less so for BaCl2 and NaCl.

scholarly journals Magnetospheric solitary structure maintained by 3000 km/s ions as a cause of westward moving auroral bulge at 19 MLT

2009 ◽  
Vol 27 (7) ◽  
pp. 2947-2969 ◽  
Author(s):  
M. Yamauchi ◽  
I. Dandouras ◽  
P. W. Daly ◽  
G. Stenberg ◽  
H. U. Frey ◽  
...  
Keyword(s):  
Ionospheric Plasma ◽  
Potential Drop ◽  
Propagation Direction ◽  
Good Correspondence ◽  
Energetic Ions ◽  
Total Potential ◽  
Geocentric Distance ◽  
Image Satellite ◽  
Magnetic Variation ◽  
Cluster Location

Abstract. In the evening equatorial magnetosphere at about 4 RE geocentric distance and 19 MLT, the four Cluster spacecraft observed a solitary structure with a width of about 1000~2000 km in the propagation direction. The solitary structure propagates sunward with about 5~10 km/s carrying sunward electric field (in the propagation direction) of up to about 10 mV/m (total potential drop of about 5~10 kV), depletion of magnetic field of about 25%, and a duskward E×B convection up to 50 km/s of He+ rich cold plasma without O+. At the same time, auroral images from the IMAGE satellite together with ground based geomagnetic field data showed a westward (sunward at this location) propagating auroral bulge at the magnetically conjugate ionosphere with the solitary structure. The solitary structure is maintained by flux enhancement of selectively 3000 km/s ions (about 50 keV for H+, 200 keV for He+, and 750 keV for O+). These ions are the main carrier of the diamagnetic current causing the magnetic depletion, whereas the polarization is maintained by different behavior of energetic ions and electrons. Corresponding to aurora, field-aligned accelerated ionospheric plasma of several keV appeared at Cluster from both hemispheres simultaneously. Together with good correspondence in location and propagation velocity between the auroral bulge and the solitary structure, this indicates that the sunward moving auroral bulge is caused by the sunward propagation of the solitary structure which is maintained by energetic ions. The solitary structure might also be the cause of Pi2-like magnetic variation that started simultaneously at Cluster location.

Sherardizing and Characteristic of Zinc Protective Coating on High-Strength Steel Bridge Cable Wires

2010 ◽  
Vol 97-101 ◽  
pp. 1368-1372 ◽  
Author(s):  
Jing Hua Jiang ◽  
Ai Bin Ma ◽  
Xin Du Fan ◽  
Ming Zi Gong ◽  
Liu Yan Zhang
Keyword(s):  
Corrosion Resistance ◽  
High Strength Steel ◽  
Protective Coatings ◽  
Steel Wire ◽  
High Strength ◽  
Steel Bridge ◽  
X Ray Diffraction ◽  
High Carbon ◽  
Bridge Cable

Zinc protective coatings on high carbon SWRH82B-1 steel were sherardized to markedly improve corrosion resistance of the high-strength steel bridge cable wires (SBCW). Sherardizing parameters have been optimized by optical microscopy (OM) /scanning electron microscopy (SEM), X-ray diffraction (XRD) and potentiodynamic polarization tests. The sherardizing coatings are composed of the loose outer layer (§-FeZn13 phase) and the dense inner layer (δ- FeZn7 phase) with higher hardness. Addition of Y2O3 activator slightly increases the corrosion resistance of sherardized steel wire in comparison with CeO2. A thicker coating corresponds to a higher sherardizing temperature or a longer heating duration, but an extra thick coating is unfavorable for thru-microcrack existed in the inner layer. Good quality of sherardized wires ( higher corrosion resistance and longer duration than conditional hot-dip-galvanized one) can be produced with the zinc-rich powder containing 7.5wt.% CeO2 activator and 25wt. % SiO2 filler under 400°Cfor 6h.

Sign in / Sign up

Export Citation Format

Share Document