The Mechanism of Corrosion and Corrosion Control of Aluminum/graphite Metal Matrix Composites PDF Download
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Author: Lawrence Christopher Dash
Publisher:
ISBN:
Category :
Languages : en
Pages : 420
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Book Description
Author: Lawrence Christopher Dash
Publisher:
ISBN:
Category :
Languages : en
Pages : 420
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Book Description
Author: K. A. Lucas
Publisher: *Research Studies Press
ISBN:
Category : Science
Languages : en
Pages : 160
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Book Description
Reviews the current state of published knowledge regarding the behavior of aluminium-based MMCs in aggressive environments, profiling potential problems and techniques of addressing them. Presents mechanisms of corrosion characteristics of aluminium and its alloys along with extensive coverage concerning the effect of the presence of a reinforcing phase on corrosion behavior of the resulting composite. Pays particular attention to important reinforcements of silicon carbide, alumina, boron, graphite and mica.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 17
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Book Description
Several commercial G/Al MMCs have been studied by potentiodynamic polarization in deaerated 0.5 M Na2SO4. The results have been compared with those which were predicted by the mixed electrode theory. The results indicate that processing conditions, especially the cooling rate, had a strong influence on the corrosion behavior of the G/Al MMCs. Large scale G/Al model MMCs were fabricated at MIT in order to study the corrosion behavior of G/Al galvanic couples with the scanning potential microprobe (SPM). Preliminary results indicate that coating graphite with discontinuous alumina did not reduce the corrosion rate of the G/Al galvanic couple. Ion implanting the surface of G/Al model MMCs with zinc, a cathodic inhibitor, did reduce the corrosion G/Al galvanic couple; however, the protection was incomplete.
Author: DM. Aylor
Publisher:
ISBN:
Category : Aluminum
Languages : en
Pages : 16
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Book Description
The corrosion resistance of graphite/aluminum (Gr/Al) and silicon carbon/aluminum (SiC/Al) metal matrix composite (MMC) materials and composite corrosion protection methods were investigated in marine environmental exposures ranging from 30 to 365 days. Accelerated corrosion of the Gr/Al resulted from galvanic interactions between the graphite fibers and the aluminum matrix. Corrosion of the SiC/Al was due to pitting, which was oriented at the silicon carbide-aluminum interfaces in the discontinuous forms of silicon carbide reinforcement. Differences in surface foil alloy and composite structure for the Gr/Al or type of silicon carbide reinforcement for the SiC/Al did not affect the materials' overall corrosion resistance. A variety of corrosion control coatings was found to be suitable for protection of the MMC, including organic and thermal-sprayed coatings.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 15
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Book Description
High modulus graphite (Gr) reinforced metal matrix composites (MMCs) offer a wide variety of attractive properties including: high specific modulus and strength (E/p and UTS/p), tailorable or zero coefficient of thermal expansion (CTE), and high thermal conductivity. Using Al as the matrix metal results in a reduction of the final density of the composite with high elastic modulus and excellent strength in the fiber direction. Unfortunately, MMCs, especially Gr reinforced composites, are extremely susceptible to corrosion with severe attack in chloride-containing environments occurring in as little time as several weeks for Gr/Al composites. The overall objective of this research is to determine whether improving the inherent passivity of the matrix metal in a Gr/Al composite can alleviate, or at least minimize, galvanic corrosion between the graphite and the matrix metal. This galvanic corrosion is currently the limiting factor in utilization of these composites. Our research focuses on the unique properties of sputter deposited alloys. With sputter deposition it is possible to significantly increase the solubility of passivity enhancing species, thus dramatically improving their corrosion resistance. The approach being undertaken is to develop alloy systems capable of minimizing galvanic degradation of the composite. An essential step in this process is identification of alloy compositions which maintain enhanced passivity after processing into the bulk composite. Our earlier work indicated that Al-Mo alloys provide the best combination of thermal stability, corrosion resistance, and alloy density. This paper will address the thermal stability and corrosion resistance of selected compositions of Al-Mo and Al-Mg-Mo alloys.
Author: C. R. Crowe
Publisher:
ISBN:
Category :
Languages : en
Pages : 19
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Book Description
Scanning vibrating electrode techniques (SVET) have been used to study corrosion in Gr/Al and SiC/Al metal matrix composites. This new technique uses vibrating probes to measure localized ionic currents with spatial and current resolutions on the order of 15 to 20 micrometers and 5nA/sq.cm, respectively. Thus, it is now possible to measure corrosion currents resulting from individual local cell activity on a scale closely related to many microstructural features of the composites. The relative severity of pits and crevices associated with the corrosion process. The observations demonstrate that corrosion effects from metallurgical variations due to welding to SiC/Al can be detected and areas of accelerated corrosion activity delineated. The observations of the corroding Gr/Al specimen imply that the corrosion rate of the composite in the absence of flaws would depend upon the catalytic properties of the graphite in promoting or retarding the oxygen reduction reaction as well as the rate of diffusion of o2 to the surface. Both the exchange current density for the reaction and the Tafel constant would affect the oxygen reduction reaction rate. Thus, the corrosion rate in the absence of flaws might be improved by additions of poisions to the fiber to retard the oxygen reduction reaction on graphite. The fact that an increase in the anodic current streaming from the flaws was detected indicates that the interface and crevice corrosion is important. Originator key words include: Corrosion, Galvanic couple, Electrochemistry.
Author: R. Winston Revie
Publisher: John Wiley & Sons
ISBN: 0470080329
Category : Technology & Engineering
Languages : en
Pages : 1299
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Book Description
This book serves as a reference for engineers, scientists, and students concerned with the use of materials in applications where reliability and resistance to corrosion are important. It updates the coverage of its predecessor, including coverage of: corrosion rates of steel in major river systems and atmospheric corrosion rates, the corrosion behavior of materials such as weathering steels and newer stainless alloys, and the corrosion behavior and engineering approaches to corrosion control for nonmetallic materials. New chapters include: high-temperature oxidation of metals and alloys, nanomaterials, and dental materials, anodic protection. Also featured are chapters dealing with standards for corrosion testing, microbiological corrosion, and electrochemical noise.
Author:
Publisher:
ISBN:
Category : Mathematics
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 26
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Book Description
This program examined the relationship between processing and chemistry in continuous fiber graphite/aluminum alloy metal mix composites (G/Al MMCs) with particular attention to subsequent effects on electrochemical behavior. In general, anodic polarization of (G/Al MMCs) compared well with mixed electrode model predictions. Deviations were associated with commercial fiber type and interfacial intermetallics. At high anodic overpotentials, graphite fiber oxidation and subsequent crevice formation resulted in large deviations from mixed-potential theory. Zinc ion implantation of graphite fibers was found to reduce the corrosion rate by a factor of twenty in NaCl solutions. Al4C3 hydrolysis was not observed on the time scale of the polarization studies performed. The scanning potential microprobe (SPM) was used to identify cathodic and anodic sites in situ for both model G/Al composites and commercial 0-90 deg interlaminar G/6061 Al MMCs. Corrosion, Graphite Aluminum Metal Matrix Composites.
Author: Lloyd H. Hihara
Publisher: CRC Press
ISBN: 1439819262
Category : Technology & Engineering
Languages : en
Pages : 722
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Book Description
One of the main, ongoing challenges for any engineering enterprise is that systems are built of materials subject to environmental degradation. Whether working with an airframe, integrated circuit, bridge, prosthetic device, or implantable drug-delivery system, understanding the chemical stability of materials remains a key element in determining their useful life. Environmental Degradation of Advanced and Traditional Engineering Materials is a monumental work for the field, providing comprehensive coverage of the environmental impacts on the full breadth of materials used for engineering infrastructure, buildings, machines, and components. The book discusses fundamental degradation processes and presents examples of degradation under various environmental conditions. Each chapter presents the basic properties of the class of material, followed by detailed characteristics of degradation, guidelines on how to protect against corrosion, and a description of testing procedures. A complete, self-contained industrial reference guide, this valuable resource is designed for students and professionals interested in the development of deterioration-resistant technological systems constructed with metallurgical, polymeric, ceramic, and natural materials.
