Search Results for electrochemical behavior

This article reviews the understanding of corrosion interactions between alloys in complex geometries and in applications where there are significant cyclic stresses and potential for wear and fretting motion. These alloys include iron-base, titanium-base, and cobalt-base alloys. The article discusses the surface characteristics and electrochemical behavior of metallic biomaterials. It summaries the clinical context for mechanically assisted corrosion and describes mechanically assisted crevice corrosion. There have been several tests developed to investigate aspects of mechanically assisted corrosion. The article also explains the scratch test and the in vitro fretting corrosion test.

Zinc is one of the most used metals, ranking fourth in worldwide production and consumption behind iron, aluminum, and copper. This article commences with an overview of the applications of zinc that can be divided into six categories: coatings, casting alloys, alloying element in brass and other alloys, wrought zinc alloys, zinc oxide, and zinc chemicals. It discusses the corrosion and electrochemical behavior of zinc and its alloys in various environments, particularly in atmospheres in which they are most widely used. The article tabulates the corrosion rates of zinc and zinc coatings immersed in various types of waters, in different solutions in the neutral pH range, and in soils at different geographic locations in the United States. It concludes with information on the forms of corrosion encountered in zinc coatings, including galvanic corrosion, pitting corrosion, and intergranular corrosion.

This article describes dental alloy compositions and its properties. It discusses the safety and efficacy considerations of dental alloy devices. The article defines and compares interstitial fluid and oral fluid environments. Artificial solutions developed for the testing and evaluation of dental materials are summarized. The article examines the effects of restoration contact on electrochemical parameters and reviews the concentration cells developed by dental alloy-environment electrochemical reactions. The composition and characterization of biofilms, corrosion products, and other debris that deposit on dental material surfaces are discussed. The article evaluates the types of alloys available for dental applications, including direct filling alloys, crown and bridge alloys, partial denture alloys, porcelain fused to metal alloys, wrought wire alloys, soldering alloys, and implant alloys. The effects of composition and microstructure on the corrosion of each alloy group are also discussed. The article concludes with information on the tarnishing and corrosion behavior of these alloys.

This article reviews the corrosion interactions between biomedical alloys, in particular iron-base, titanium-base, and cobalt-base alloys, in complex geometries and in applications where there are significant cyclic stresses and potential for wear and fretting motion. It discusses the nature of these metal surfaces and their propensity for corrosion reactions when combined with similar or different alloys in complex restrictive environments within the human body and under loading conditions. The article describes the factors that influence mechanically assisted crevice corrosion. It reviews the tests developed to investigate the aspects of mechanically assisted corrosion of metallic biomaterials: the scratch test and the in vitro fretting corrosion test.

This article describes the methods of wear measurements and a model of corrosive wear in mill atmospheres. It explains the polarization curves of pyrrhotite and high-carbon low-alloy steel in a quartzite slurry with examples. The surfaces of pyrrhotite in contact with mild steel or stainless steel affected by galvanic interaction are discussed. The article contains a table that lists the results of laboratory marked ball wear tests for three types of steel balls in wet grinding of magnetic taconite. It also provides information on the mechanism of electrochemical interaction and relative significance of corrosion and abrasion in wear. Galvanic interactions in multielectrode systems are reviewed. The article presents a case history on the material selection for grinding balls to minimize corrosion loss and the adverse effect on flotation.

This article provides a background of the complex relationship between titanium and its alloys with aqueous environments, which is dictated by the presence of a passivating oxide film. It describes the corrosion vulnerability of titanium and titanium oxides by the classification of oxide failure mechanisms. The mechanisms are spatially localized oxide film breakdown by the ingress of aggressive anions; spatially local or homogenous chemical dissolution of the oxide in a strong reducing-acid environment; and mechanical disruptions or depassivation such as scratching, abrading, or fretting. Titanium alloys can be classified into three primary groups such as titanium alloys with hexagonal close-packed crystallographic structure; beta titanium alloys with body-centered cubic crystallographic structures; and alpha + beta titanium alloys including near-alpha and near-beta titanium alloys. The article also illustrates the effects of alloying on active anodic corrosion of titanium and repassivation behavior of titanium and titanium-base alloys.

This article tabulates the chemical composition of iron-base, titanium-base, and cobalt-base alloys and illustrates the microstructures of these materials. It discusses the surface morphology and chemistry of oxide-film-covered alloys and provides insights into the interaction. The article illustrates the interfacial structure of a biomaterial surface contacting with the biological environment. It describes the corrosion behavior of stainless steel, cobalt-base alloy, and titanium alloys. The electrochemical methods used for studying metallic biomaterials corrosion are also discussed. The article concludes with information on the biological consequences of in vivo corrosion and biocompatibility.

This article explores the use of the electrochemical and nonelectrochemical techniques for measuring the corrosion behavior of buried metals and the types of probes used. The electrical resistance technique is the main nonelectrochemical technique used for measuring corrosion rate. Electrochemical techniques discussed include linear polarization resistance, electrochemical noise, harmonic distortion analysis, electrochemical impedance spectroscopy, and hydrogen permeation. The principles of operation for the corrosion measuring techniques are described along with examples of their use in soils.

This article provides an overview of the degradation of metals and alloys in aqueous systems. The importance of the hydrogen ion lies in its ability to interact with an alloy surface. The article describes the effects of various conditions of pH on corrosion including strongly acid conditions, near-neutral conditions, and strongly basic conditions as well as the effects of temperature on corrosion. The influence of the fluid flow rate on corrosion depends on the alloy, fluid components, fluid physical properties, geometry in which the fluid is contained, and corrosion mechanism. The article discusses the influence of fluid flow rate through specific examples. It concludes with information on how the concentration of dissolved species works with other variables to influence corrosion behavior.

This article describes the various factors that affect the extent of corrosion resulting from galvanic coupling. The factors include galvanic series, polarization behavior, and geometric relationship of metals and alloys. The article briefly discusses the various modes of attack that lead to galvanic corrosion of anodic members. It also explains the three electrochemical techniques of screening tests for predicting galvanic corrosion. The electrochemical techniques comprise of potential measurements, current measurements, and polarization measurements. The article provides a detailed discussion on the performance of alloy groupings. It concludes with information on various control methods that reduce or eliminate galvanic-corrosion effects.

Chemical-mechanical planarization (CMP) of metals is described as mechanically accelerated corrosion, erosion corrosion, or metallic corrosion enhanced by wear. This article reviews the history, process, chemistry, electrochemistry, and defect issues for CMP. It provides an overview of CMP through a schematic illustration of CMP process equipment. The applications of CMP to tungsten and copper alloys are of prime interest in the semiconductor industry. The article discusses copper CMP and tungsten CMP in detail and analyzes polishing mechanism during CMP by application of direct current potentiodynamic polarization and alternating current impedance measurements. It concludes with information on chemically induced defects such as pitting corrosion, galvanic corrosion, and chemical etching.

Dealloying is a corrosion process in which one or more elements are selectively dissolved, leaving behind a porous residue of the remaining elements. This article describes the dealloying in various systems, namely, dezincification, graphitic corrosion, dealuminification, and noble metal alloys dealloying. The current-potential behavior of a binary alloy undergoing selective dissolution is reviewed. The article highlights the four mechanisms required for the formation of porous metals: ionization-redeposition, surface diffusion, volume diffusion, and percolation model of selective dissolution.

This article focuses on the testing and typical corrosion behavior of coating-substrate systems in aqueous solutions and humid aggressive atmospheres. It includes a short review of the fundamentals of corrosion, followed by a discussion of specific system behavior, electrochemical and laboratory accelerated tests, and simulated service tests. The article also contains examples of different types of corrosion damage and presents guidelines for improving corrosion resistance.

This article reviews the corrosion behavior in various environments for seven important nickel alloy families: commercially pure nickel, Ni-Cu, Ni-Mo, Ni-Cr, Ni-Cr-Mo, Ni-Cr-Fe, and Ni-Fe-Cr. It examines the behavior of nickel alloys in corrosive media found in industrial settings. The corrosive media include: hydrochloric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, hydrobromic acid, nitric acid, organic acids, salts, seawater, and alkalis. The modes of high-temperature corrosion include oxidation, carburization, metal dusting, sulfidation, nitridation, corrosion by halogens, and corrosion by molten salts. Applications where the corrosion properties of nickel alloys are important factors in materials selection include the petroleum, chemical, and electrical power industries. Most nickel alloys are much more resistant than the stainless steels to reducing acids, such as hydrochloric, and some are extremely resistant to the chloride-induced phenomena of pitting, crevice attack, and stress-corrosion cracking (to which the stainless steels are susceptible). Nickel alloys are also among the few metallic materials able to cope with hot hydrofluoric acid. The conditions where nickel alloys suffer environmentally assisted cracking are highly specific and therefore avoidable by proper design of the industrial components.

This article describes the selection of materials for the production and handling equipment of concentrated sulfuric acid, depending on factors such as the allowable corrosion rate, desired mechanical and physical properties, fabrication requirements, availability, and cost. Materials such as carbon steel, cast irons, austenitic stainless steels, higher austenitic stainless steels, higher chromium Fe-Ni-Mo alloys, nickel-base alloys, non-metals, and specific other metals and alloys are also discussed.

This article provides a discussion on the fundamentals of corrosion thermodynamics. The discussion focuses on electrochemical reactions, molten salt corrosion thermodynamics, and geochemical modeling.