Showing papers on "Corrosion published in 1998"

Corrosion of metal orthopaedic implants.

Abstract: In situ degradation of metal-alloy implants is undesirable for two reasons: the degradation process may decrease the structural integrity of the implant, and the release of degradation products may elicit an adverse biological reaction in the host Degradation may result from electrochemical dissolution phenomena, wear, or a synergistic combination of the two Electrochemical processes may include generalized corrosion, uniformly affecting the entire surface of the implant, and localized corrosion, affecting either regions of the device that are shielded from the tissue fluids (crevice corrosion) or seemingly random sites on the surface (pitting corrosion) Electrochemical and mechanical processes (for example, stress corrosion cracking, corrosion fatigue, and fretting corrosion) may interact, causing premature structural failure and accelerated release of metal particles and ions The clinical importance of degradation of metal implants is evidenced by particulate corrosion and wear products in tissue surrounding the implant, which may ultimately result in a cascade of events leading to periprosthetic bone loss Furthermore, many authors have reported increased concentrations of local and systemic trace metal in association with metal implants1,4,5,9-11,14,18,25,26,28,29,47,49-55,58,71,72,75-77,87,90,108-110 There also is a low but finite prevalence of corrosion-related fracture of the implant This review focuses on electrochemical corrosion phenomena in alloys used for orthopaedic implants A summary of basic electrochemistry is followed by a discussion of retrieval studies of the response of the implant to the host environment and the response of local tissue to implant corrosion products The systemic implications of the release of metal particles also are presented Finally, future directions in biomaterials research and development …

Modeling the time-to-corrosion cracking in chloride contaminated reinforced concrete structures

Abstract: The time-to-cracking, from corrosion initiation to cracking of the reinforcing steel cover concrete, is one of the critical time periods for modeling the time to repair, rehabilitate, and replace reinforced concrete structures in corrosive environments. The time to corrosion cracking was experimentally determined from simulated bridge deck slabs. The experimental design considered corrosion rate, concrete cover depth, reinforcing steel bar spacing, and size. Three of the 14 slab series cracked during the 5-year study. Metal loss was determined for the cracked specimens that had cover depths of 1 in (25 mm), 2 in (51 mm), and 3 in (76 mm). A time to corrosion cracking model was developed that considered the critical amount of corrosion products that consists of the amount of corrosion products needed to fill the interconnected void space around the reinforcing bar plus the amount of corrosion products needed to generate sufficient tensile stresses to crack the cover concrete. The experimentally observed time to cracking is in good agreement with the model predicted time to cracking.

Characterization of Iron Oxides Commonly Formed as Corrosion Products on Steel

Abstract: For fundamental studies of the atmospheric corrosion of steel, it is useful to identify the iron oxide phases present in rust layers. The nine iron oxide phases, iron hydroxide (Fe(OH)2), iron trihydroxide (Fe(OH)3), goethite (α-FeOOH), akaganeite (β-FeOOH), lepidocrocite (γ-FeOOH), feroxyhite (δ-FeOOH), hematite (α-Fe2O3), maghemite (γ-Fe2O3) and magnetite (Fe3O4) are among those which have been reported to be present in the corrosion coatings on steel. Each iron oxide phase is uniquely characterized by different hyperfine parameters from Mossbauer analysis, at temperatures of 300K, 77K and 4K. Many of these oxide phases can also be identified by use of Raman spectroscopy. The relative fraction of each iron oxide can be accurately determined from the Mossbauer subspectral area and recoil-free fraction of each phase. The different Mossbauer geometries also provide some depth dependent phase identification for corrosion layers present on the steel substrate. Micro-Raman spectroscopy can be used to uniquely identify each iron oxide phase to a high spatial resolution of about 1 µm.

Factors controlling cracking of concrete affected by reinforcement corrosion

Abstract: The present paper tries to contribute to quantifying the relationship between the amount of corrosion and cover cracking. The variables studied were: cover/diameter (c/o), proportions of cement, w/c, cast position of the bar, transverse reinforcement and corrosion rate. The corrosion is accelerated by applying constant currents causing the rebar to act as an anode. The results indicate that the cracking process develops in two steps: generation and propagation. Radius losses of about 15–50 μm are necessary to generate the first visible crack (<0.1 mm width). The propagation follows a behaviour of the type: w (crack width in mm)=a+bx (radius loss in μm).

Corrosion inhibitors : principles and applications

Abstract: Corrosion Inhibition -- Historical Aspects. An Overview of Corrosion Inhibition. Electrochemical Principles. Chemical Aspects of Corrosion Inhibition. Surface Analysis and Composition of Inhibitor Films. Quality Control of Corrosion Inhibitors. Corrosion Tests. Inhibition of Localized Corrosion. Inhibition of Stress Corrosion Cracking. Inhibition by Macrocyclics and Rare Earth Metal Compounds. Biocides. Oxygen Scavengers. Expert Systems for Corrosion Control. Applications. Corrosion Inhibition of Copper. Economic Considerations. Environmentally--Friendly Inhibitors. Index.

Iron aluminides: present status and future prospects

Abstract: This paper constitutes a broad survey of the physical, mechanical and corrosion properties of Fe3Al alloys, as well as a review of principal processing methods. This class of alloys, once thought to be inherently brittle, is shown to possess moderate ductility, provided that mechanical testing is carried out in an inert environment. Methods to improve mechanical properties by alloying and microstructural control are described. The influence of alloying elements on corrosion and stress corrosion resistance and weldability also is reviewed.

Effect of modification of oxide layer on NiTi stent corrosion resistance.

Abstract: Because of its good radiopacity, superelasticity, and shape memory properties, nickel-titanium (NiTi) is a potential material for fabrication of stents because these properties can facilitate their implantation and precise positioning. However, in vitro studies of NiTi alloys report the dependence of alloy biocompatibility and corrosion behavior on surface conditions. Surface oxidation seems to be very promising for improving the corrosion resistance and biocompatibility of NiTi. In this work, we studied the effect on corrosion resistance and surface characteristics of electropolishing, heat treatment, and nitric acid passivation of NiTi stents. Characterization techniques such as potentiodynamic polarization tests, scanning electron microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy were used to relate corrosion behavior to surface characteristics and surface treatments. Results show that all of these surface treatments improve the corrosion resistance of the alloy. This improvement is attributed to the plastically deformed native oxide layer removal and replacement by a newly grown, more uniform one. The uniformity of the oxide layer, rather than its thickness and composition, seems to be the predominant factor to explain the corrosion resistance improvement.

Processing and properties of particulate reinforced steel matrix composites

Abstract: Metal matrix composites are an attractive choice for aerospace and automotive applications because of their high stiffness-to-weight ratio. Composites with aluminum and magnesium matrices have been investigated extensively, while less work has been carried out on steel matrix composites. In the present study the hot isostatic pressing (HIP) process of steel matrix composites is described, and the factors influencing the reinforcement distribution, interface processes, as well as the mechanical and corrosion properties, are revealed. Both stainless steels and tool steels were used as the matrix material, and the particulate reinforcements were Al 2 O 3 , TiC, Cr 3 C 2 , or TiN. The results are compared with those of the corresponding unreinforced alloys and also with those of aluminum and magnesium matrix composites. It was found that the incorporation of a relatively low volume fraction of ceramic particulate reinforcements significantly increases the wear resistance of the steel matrices, without deteriorating the corrosion properties. On the other hand, reductions in the tensile strength, ductility and toughness were observed. The superaustenitic stainless steel–TiN and hot work tool steel–Cr 3 C 2 composites may offer the best combination of properties.

Green Corrosion Inhibitors: Theory and Practice

Abstract: Sastri, V. S. 2011. Hardback, John Wiley & Sons, Inc, 328pp. ISBN 978-0470-45210-3 £66?95 J80?40 This is the book that the international corrosion community has been waiting for. A text that throws a new light on the crucial problems of corrosion that strongly affect natural and industrial environments. Today, it is generally accepted that corrosion and pollution are interrelated harmful processes since many pollutants accelerate corrosion and corrosion products such as rust, also pollute water bodies. Both are pernicious processes that impair the quality of the environment, the efficiency of the industry and the durability of the infrastructure assets. Therefore, it is essential to develop and apply corrosion engineering control methods and techniques, in particular safe green corrosion inhibitors. In this crucial time of energy crisis and economic turmoil, cost-effective corrosion control will extend the life of the infrastructure saving large expenses in materials, equipment and structures. Dr. V. S Vedula Sastri is a member of the Metallurgical Society of the Canadian Institute of Mining and Metallurgy and a consultant at Sai Ram Consultants. His volume belongs to the advanced field of ‘green chemistry’ also known as sustainable chemistry, involving the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances. Green chemistry technologies provide a number of benefits; depressed waste, safer products, saving resources and energy, improved chemical manufacture and so on. This publication is well-organised and consists of seven parts, starting with the basics of corrosion and a description of corrosion forms followed by the electrochemical principles of corrosion and its monitoring, applying intrusive and nonintrusive techniques. A section is devoted to the influence of corrosion by the characteristics of the corrosive fluids, their chemical composition, flow regime, velocity and process parameters: pressure, temperature, dew point and fouling. The core of this volume appears in chapters three, four and five dealing profusely with the theory and practice of corrosion inhibition, their adsorption at the metal surface and their corrosion inhibition mechanism in different media: acidic, neutral and alkaline. Numerous applications of corrosion inhibitors are recorded in chapter 6 such as reinforced steel in concrete, in cooling water systems, in coal-water slurries, in acid pickling equipment, as additives to paints and coatings to enhance their corrosion protection properties. As chemical engineers and corrosion professionals active in corrosion research and environmental and industrial corrosion control we benefited from reading chapter seven on environmentally friendly corrosion inhibitors. It presents the activities of the European Economic Community and the creation of the Paris Commission (PARCOM) with the important aim to develop and implement guidelines for testing the toxicity, biodegradation and bioaccumulation of corrosion inhibitors, standards for environmental testing and models to use in industrial practice. In this context, it is interesting to note that Dr. Sastri calls the environment friendly inhibitors ‘green’ but toxic inhibitors are termed ‘gray’. Table 7?13 offers many green inhibitors derived from plant products, generated by solvent extraction techniques. An additional, modern classification of inhibitors considers them as hard, soft and borderline. The book is copiously illustrated, displaying numerous figures, diagrams, photographs, and graphs, many related to the author’s professional experience and activities. We should mention the large number of tables, heavy in information, listing hundreds of practical uses for corrosion inhibitors. They contribute to a clear, lucid reading and understanding, making this a valuable text, for both professionals and students of engineering, science, chemistry and metallurgy. The book is enriched by an amazing number of references: 909; some of historical value, other illustrating fundamental aspects and actual industrial practice. If a second edition is to be published as this subject and book deserve, it would be convenient to add: N A glossary of term related to water, corrosion, electrochemistry, corrosion inhibition, paints and coatings. N The International Unified Numbering System (UNS), widely accepted, for the designation of the metals and alloys displayed in the book. N Expansion of the paragraph ‘Corrosion control in the electronics industry’ (Chapter 7) since corrosion of the contacts connectors, wires of electronic devices impair these components. There is no human activity: industrial production, energy generation, water supply, transportation and communication systems, infrastructure maintenance, health care, education services, economy management that is not provided with electronic equipment. Green corrosion inhibitors will prevent or mitigate this corrosion damage. Dr. Benjamin Valdez Salas Director and Professor, Institute of Engineering, University of Baja California, Mexico Dr. Michael Schorr Wiener Professor, Institute of Engineering, University of Baja California, Mexico If you would like to review a book for Corrosion Engineering Science and Technology please contact the Managing Editor, mailto:Emma Leighton, at e.leighton@maney.co.uk.

Corrosion of magnesium alloys containing rare earth elements

Abstract: Magnesium forms solid solutions or intermetallic compounds with a number of rare earth (RE) elements. In addition to their beneficial effect on castability, elevated temperature tensile and creep properties, RE elements improve the corrosion resistance of magnesium. The corrosion behavior of several types of RE containing Mg alloys such as WE and AE series are analyzed. While most of the corrosion mechanism have been discussed in terms of intermetallics or RE enrichment of oxide film, the authors consider the formation of magnesium hydride (MgH2) layer as an important contribution of RE elements. This hypothesis is analyzed with several experimental results. The effect of alloying element, heat treatment including rapid solidification processing are also reviewed.

Corrosion Protection of Untreated AA‐2024‐T3 in Chloride Solution by a Chromate Conversion Coating Monitored with Raman Spectroscopy

Abstract: This work was supported by the Air Force Office of Scientific Research, contract no. F49620-96-1-0479.

A transmission electron microscopy study of constituent-particle-induced corrosion in 7075-T6 and 2024-T3 aluminum alloys

Abstract: To better understand particle-induced pitting corrosion in aluminum alloys, thin foil specimens of 7075-T6 and 2024-T3 aluminum alloys, with identified constituent particles, were immersed in aerated 0.5M NaCl solution and then examined by transmission electron microscopy (TEM). The results clearly showed matrix dissolution around the iron- and manganese-containing particles (such as Al23CuFe4), as well as the Al2Cu particles. While Al2CuMg particles tended to dissolve relative to the matrix, limited local dissolution of the matrix was also observed around these particles. These results are consistent with scanning electron microscopy (SEM) observations of pitting corrosion and are discussed in terms of the electrochemical characteristics of the particles and the matrix.

Wear‐Accelerated Corrosion of Passive Metals in Tribocorrosion Systems

Abstract: A model is presented which describes the effect of mechanical and materials parameters on the wear‐assisted corrosion rate of passive metals under sliding wear conditions. The model is based on a consideration of contact between the sliding surfaces at multiple asperities and it takes into account the passivation behavior of the metal. Wear experiments were carried out in a reciprocating pin‐on‐plate tribometer permitting the control of mechanical and electrochemical conditions. An alumina pin was rubbed on nickel, chromium, stainless steel, and titanium alloy plates, in sulfuric acid or sodium sulfate solution. The relative importance of mechanical and electrochemical metal removal was evaluated while applying an anodic potential. Additional experiments were performed under cathodic polarization. The results show that the proposed model can describe correctly the effect on dissolution rate of different mechanical parameters such as applied normal force, stroke length, frequency, and sliding speed. Qualitative agreement was observed with the predicted effect of the materials parameters hardness and passivation charge, but uncertainties concerning the real value of passivation charge and, in some cases, wear of the alumina pin limit the predictive capability of the model when comparing different materials. The experimental results obtained in this study demonstrate that to understand the mutual interactions between mechanical and electrochemical parameters affecting wear‐accelerated corrosion it is necessary to look at the tribocorrosion system as a whole.

Surface modification of titanium alloys for combined improvements in corrosion and wear resistance

Abstract: A simple and effective surface modification technique, namely palladium-treated thermal oxidation (PTO), has been developed in the present research. Comparative investigations on both corrosion and wear resistance have been carried out on surface-engineered titanium-based materials by conventional plasma nitriding (PN), thermal oxidation (TO), and the newly developed palladium-treated thermal oxidation (PTO). Both the TO- and PTO-treated materials have a significantly superior corrosion resistance in boiling HCl solutions compared to the PN-treated and untreated materials. The lifetime for the protective surface layer breakdown of the TO-treated titanium in boiling 20% HCl solution is about 13 times that of the PN-treated titanium, whereas the lifetime of the PTO-treated material has been increased further by a factor of 2.6 over the TO-treated material. The PTO-treated material has shown a better anti-scuffing capacity than the TO-treated material under oil-lubricated conditions. Characterisation of both the TO- and PTO-treated surface layers was performed using glow discharge spectrometry (GDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Role of Conductive Corrosion Products in the Protectiveness of Corrosion Layers

Abstract: In carbon dioxide (CO2) corrosion of steels, the bicarbonate ion (HCO3−) is simultaneously the buffer for carbonic acid (H2CO3), the source of iron carbonate (FeCO3) precipitation, and the product of the cathodic reaction. In addition to spatial separation of the production of Fe2+ and HCO3−, galvanic coupling between the steel and cementite (Fe3C) layers is the principal cause of internal acidification in these layers, since the HCO3− ions are removed from the steel surface by electromigration. This can facilitate localized corrosion by lateral galvanic coupling. This mechanism explains the role of traces of free acetic acid (CH3COOH, or HAc) and the existence of multiple steady states. Transposition to corrosion of iron by hydrogen sulfide (H2S) or to corrosion of copper is discussed.

Critical factors affecting the high-temperature corrosion performance of iron aluminides

Abstract: Iron aluminides are known to exhibit good-to-excellent corrosion resistance in a number of high-temperature environments. Under most conditions, this resistance derives from the establishment and maintenance of a sound and adherent alumina layer. Consequently the performance of iron aluminides under different aggressive high-temperature can be related to fundamental factors that affect the development, adhesion, and durability (lifetime) of protective alumina. Overall corrosion resistance depends not only on thermodynamic stability of the reaction product in a particular environment and its growth kinetics, but also on scale integrity and morphology, the chemical and physical nature of the oxide–metal interface, alloy strength, and the specific composition of the iron aluminide. Despite the multiplicity of factors, a relatively simple lifetime prediction model based on aluminum consumption can be used to evaluate the influences of changes in material parameters and to determine approaches to improving high-temperature corrosion resistance of iron aluminides.