Long-term immersion corrosion of irons and steel in seawaters with calcareous deposition

CORROSION ◽  
10.5006/3685 ◽  
2021 ◽  
Author(s):  
Robert Melchers
Keyword(s):  
Direct Evidence ◽  
Low Permeability ◽  
Microbiological Corrosion ◽  
Wrought Iron ◽  
Corrosion Rates ◽  
Immersion Corrosion ◽  
Moderate Power ◽  
Power Law Function ◽  
Ferrous Carbonate

The marine immersion corrosion of irons and steel under calcareous deposition (principally calcium carbonate) is known to be relatively low for shorter exposures (e.g. a few years). Herein the effect of calcareous deposition on corrosion is considered for exposures up to 1300 years. The data are derived from archaeological steel and iron shipwrecks, cast iron cannons and cannonballs, and wrought iron anchors in locations where there was direct evidence, in and on the corrosion products, of calcareous deposition. Such deposition promotes formation of calcium and ferrous carbonate layers of low permeability on and within rusts. These tend to inhibit both early and long-term corrosion rates. The data show that up to about 200y exposure corrosion losses as a function of time can be approximated closely by a linear function of time. Longer exposures follow a moderate power-law function, consistent with diffusion considerations. Comments are made about the likely interplay between calcareous deposition and microbiological corrosion.

Corrosion of steels and irons immersed in natural seawater for up to 600 years

CORROSION ◽  
10.5006/3967 ◽  
2021 ◽  
Author(s):  
Robert Melchers
Keyword(s):  
Power Law ◽  
Seawater Temperature ◽  
Bridge Piers ◽  
Natural Seawater ◽  
Outward Diffusion ◽  
Wrought Iron ◽  
Corrosion Loss ◽  
Immersion Corrosion ◽  
Anaerobic Corrosion

Marine immersion corrosion observations for archaeological and other data, including from shipwrecks, wrought iron anchors and cast iron bridge piers are used to estimate corrosion losses in natural unpolluted coastal and near-coastal seawaters for exposures up to about 600 years. Empirical functions for the development of corrosion loss with time were then developed, standardized to 20˚C mean seawater temperature. The resulting slightly non-linear corrosion loss trend, represented by a modified form of the power law, is consistent with Phase 4 of the previously proposed bi-modal corrosion model. These observations support the notion that the rate of long-term corrosion is controlled by outward diffusion, through the rust layers, of gaseous hydrogen generated by the cathodic hydrogen evolution reaction under predominantly anaerobic corrosion conditions. The power-law trend also provides good extrapolation from shorter- term data. For practical purposes for exposures < 100 years in seawaters with mean temperature around 20˚C, a linear model, with longer-term corrosion rate 0.06 mm/y at 20˚C, is sufficiently accurate.

Subcritical Crack Growth and Long-Term Strength in Rock and High-Strength and Ultra Low-Permeability Concrete

2009 ◽  
Vol 58 (6) ◽  
pp. 525-532 ◽  
Author(s):  
Yoshitaka NARA ◽  
Masafumi TAKADA ◽  
Daisuke MORI ◽  
Hitoshi OWADA ◽  
Tetsuro YONEDA ◽  
...  
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
High Strength ◽  
Low Permeability ◽  
Term Strength

scholarly journals Assessing Stream-Aquifer Connectivity in a Coastal California Watershed

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 416
Author(s):  
Bwalya Malama ◽  
Devin Pritchard-Peterson ◽  
John J. Jasbinsek ◽  
Christopher Surfleet
Keyword(s):  
Time Series ◽  
Spectral Analysis ◽  
Water Level ◽  
Time Series Data ◽  
Series Data ◽  
Low Permeability ◽  
Pumping Tests ◽  
Stream Flows ◽  
The Impact

We report the results of field and laboratory investigations of stream-aquifer interactions in a watershed along the California coast to assess the impact of groundwater pumping for irrigation on stream flows. The methods used include subsurface sediment sampling using direct-push drilling, laboratory permeability and particle size analyses of sediment, piezometer installation and instrumentation, stream discharge and stage monitoring, pumping tests for aquifer characterization, resistivity surveys, and long-term passive monitoring of stream stage and groundwater levels. Spectral analysis of long-term water level data was used to assess correlation between stream and groundwater level time series data. The investigations revealed the presence of a thin low permeability silt-clay aquitard unit between the main aquifer and the stream. This suggested a three layer conceptual model of the subsurface comprising unconfined and confined aquifers separated by an aquitard layer. This was broadly confirmed by resistivity surveys and pumping tests, the latter of which indicated the occurrence of leakage across the aquitard. The aquitard was determined to be 2–3 orders of magnitude less permeable than the aquifer, which is indicative of weak stream-aquifer connectivity and was confirmed by spectral analysis of stream-aquifer water level time series. The results illustrate the importance of site-specific investigations and suggest that even in systems where the stream is not in direct hydraulic contact with the producing aquifer, long-term stream depletion can occur due to leakage across low permeability units. This has implications for management of stream flows, groundwater abstraction, and water resources management during prolonged periods of drought.

Prediction of Hydraulic Conductivity of Fly Ash Built-in Mineral Sealing Layers

2017 ◽  
Author(s):  
Mariola Wasil
Keyword(s):  
Fly Ash ◽  
Hydraulic Conductivity ◽  
Laboratory Tests ◽  
Physical Parameters ◽  
Low Permeability ◽  
Empirical Formulas ◽  
Semi Empirical ◽  
Sealing Layer ◽  
Compaction Method

Mineral barrier protects the groundwater and soil from contamination by insulating the leakage of harmful substances from landfill. One of the most important parameters, which decides about usefulness of material to built-in sealing layers, is hydraulic conductivity. Researchers have conducted investigations with the possibility of utilising fly ash as a mineral sealing layer material, which is justified by its low permeability and other properties. It is known that laboratory tests of hydraulic conductivity are often long-term and require expensive equipment. Therefore, to avoid this, researchers trying to assess permeability of tested material with empirical or semi empirical formulas. The aim of the paper is to compare the results of hydraulic conductivity of fly ash obtained from the laboratory tests and from estimation using different empirical formulas. Fly ash was compacted by the Standard Proctor compaction method at the optimum moisture content. The results obtained from empirical equations were variable. It was observed that the Kozeny-Carman formula and other, based on a few physical parameters of the soil, gave better results in prediction of hydraulic conductivity of fly ash than equations based on only one parameter.

The Bubble Act: Its Passage and Its Effects on Business Organization

1994 ◽  
Vol 54 (3) ◽  
pp. 610-627 ◽  
Author(s):  
Ron Harris
Keyword(s):  
Turning Point ◽  
Direct Evidence ◽  
Economic Effects ◽  
Joint Stock Company ◽  
Stock Company ◽  
Short Term ◽  
Dominant Position ◽  
South Sea ◽  
Conversion Scheme

By surveying contemporary sources this article reveals direct evidence for the involvement of the South Sea Company in the passage of the Bubble Act. The dominant position of the Company and of its national debt conversion scheme in the affairs of England in 1720 support the conclusion that the act was in fact a piece of special-interest legislation for the Company. The short-term interest that motivated the enactment, together with the limited legal and economic effects of the act, minimized its significance as a turning point in the long-term development of the English joint-stock company.

Spent Fuel Corrosion Behavior in Salt Solution in the Presence of Hydrogen Overpressure

2001 ◽  
Author(s):  
Andreas Loida ◽  
Bernd Grambow ◽  
Horst Geckeis
Keyword(s):  
Gas Phase ◽  
Spent Fuel ◽  
Nacl Solution ◽  
Release Rates ◽  
Corrosion Rates ◽  
The Matrix ◽  
Matrix Bound ◽  
Safety Assessments ◽  
Container Material

Abstract The simultaneous corrosion of spent fuel and Fe-based container material is characterized by the formation of large amounts of hydrogen, which control the composition of the gas phase. Various experimental data indicate that the matrix dissolution rate and the release rates of important radionuclides decrease, if the H2 overpressure increases. To quantify to what extent the hydrogen overpressure may counteract radiolysis enhanced matrix dissolution rates, and to take credit from the effect of hydrogen overpressure in long-term safety assessments of the repository, a detailed experimental investigation has been initiated. High burnup spent fuel is being corroded under anoxic conditions in the absence of carbonate in 5m NaCl solution under an external H2 overpressure of 3.3 bar. This pressure is in the same range as observed in a long-term test using spent fuel and Fe-powder. Results obtained after 117 days of testing show that due to constant or decreasing concentrations of Sr and other matrix bound radionuclides, corrosion rates were not measurable indicating a stop of matrix dissolution or very low long-term rates. Grain boundary release of Cs and fission gases was found to continue under hydrogen overpressure. Compared to tests in the absence of hydrogen solution concentrations decreased by about ca. 1.5 orders of magnitude for U (10−8 M), Am, Eu (10−10 M), whereas the decrease of Np (3×10−10 M), Tc (5×10−9 M) and Pu (4×10−9 M) concentrations was found to be less significant.

Purchasing IPOs with Commissions

2011 ◽  
Vol 46 (5) ◽  
pp. 1193-1225 ◽  
Author(s):  
Michael A. Goldstein ◽  
Paul Irvine ◽  
Andy Puckett
Keyword(s):  
Initial Public Offerings ◽  
Direct Evidence ◽  
Round Trip ◽  
Public Offerings ◽  
Client Relationships ◽  
To Receive

AbstractWe find direct evidence that institutions increase round-trip stock trades, increase average commissions per share, and pay unusually high commissions on some trades in order to send abnormally high commissions to the lead underwriters of profitable initial public offerings (IPOs). These excess commission payments are a particularly effective way for transient investors to receive lucrative IPO allocations. Our results suggest that the underwriter’s concern for their long-term client relationships limits the payment-for-IPO practice. We estimate that abnormal commission payments are large for the most profitable issues, and that an additional $1 excess commission payment to the lead underwriter results in $2.21 in investor profits from allocated shares.

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