Search Results for electrochemical impedance measurement

The interaction of an implant with the human body environment may result in degradation of the implant, called corrosion. This article discusses the corrosion testing of metallic implants and implant materials. The corrosion environments for medical implants are the extracellular human body fluids, very complex solutions containing electrolytes and nonelectrolytes, inorganic and organic constituents, and gases. The article describes the fundamentals of electrochemical corrosion testing and provides a brief discussion on various types of corrosion tests. It illustrates corrosion current density determination by Tafel extrapolation, potentiodynamic measurement of the polarization resistance, electrochemical impedance measurement, and potentiostatic deaeration. Tests combining corrosion and mechanical forces, such as fretting corrosion tests, environment-assisted cracking tests, and ion-leaching tests are also discussed.

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.

A variety of electrochemical techniques are used to detect and monitor material deterioration in service or in the field. This article describes the static or direct current measurements in a number of applications, including buried pipelines and storage tanks. It reviews the electrochemical impedance spectroscopy and electrochemical noise measurements in a laboratory, especially for the inspection of coatings.

This article addresses electrochemical methods for instantaneous rate determination and threshold determination as well as nonelectrochemical methods that can determine incremental or cumulative rates of corrosion. Electrochemical methods for the study of galvanic corrosion rates and localized corrosion and evaluation of corrosion rates under paints are also discussed. The article describes nonelectrochemical methods that can determine incremental or cumulative rates of corrosion. Methods presented include polarization methods, polarization resistance methods, electrochemical impedance methods, frequency modulation methods, electrochemical noise resistance, potential probe methods, cyclic potentiodynamic polarization methods, potentiostatic and galvanostatic methods, electrochemical noise (EN) methods, scratch-repassivation method, and electrochemical impedance spectroscopy (EIS) techniques. Gravimetric determination of mass loss, electrical-resistance methods, magnetic methods, quartz crystal microbalance method, solution analysis methods, and metrological methods are nonelectrochemical methods. The article presents an electrochemical test that examines the susceptibility of stainless steel alloys to intergranular corrosion.

This article reviews the fundamentals of electrochemical corrosion test methods. The features and requirements of the instrumentation needed for an electrochemical test are briefly discussed. The article provides a discussion on the various electrochemical techniques and tests available for laboratory studies of corrosion phenomena. The techniques and tests include no-applied-signal tests, small-signal polarization tests, large-signal polarization tests, scanning electrode techniques, and miscellaneous techniques.

This article describes the criteria for selecting a corrosion-monitoring method used in industrial plants. It provides a detailed discussion on the design, advantages, and disadvantages of plant corrosion-testing program. The basic types of racks used to support and insulate the coupons are also discussed. The analysis of electrical-resistance probes, sentry holes, side-stream loop, electrochemical noise, hydrogen-probe, and process streams are used to monitor and estimate corrosion rates. The corrosion rates can also be estimated by ultrasonic thickness measurements, polarization-resistance measurements, corrosion potential measurements, and alternating current impedance measurements. Corrosion monitoring strategies, such as locations, data analysis, redundancy, and other issues, are discussed. The article concludes with information on the interpretation and reporting of corrosion testing.

This article focuses on the methods that are being developed for detecting and monitoring corrosion: electrochemical methods, electromagnetic or sound wave methods, fiber-optic technology, fluorescence methods, and the Diffracto Sight method. It reviews the importance of data management and the Corrosion Expert System. It concludes with information on the simulation and modeling for incorporating the mechanisms of corrosion prevention into military hardware systems design and operation.

Corrosion of metallic materials is governed by electrochemical kinetics, so that the general concepts developed for studying electrochemical reaction mechanisms may be applied to corrosion. This article presents the fundamental aspects of electrode kinetics. The processes of charge transfer taking place at the electrode interface within the double layer and of mass transport at the vicinity of the electrode surface are discussed. The article describes the corrosion processes, which involve anodic and cathodic reactions at specific electrode sites. Some experimental methods for devising a reliable reaction model are detailed. The article explains some reaction mechanisms for cathodic and anodic processes to illustrate the great variety of reaction mechanisms occurring at the electrode interface.

This article describes the two commonly used standardized tests for determining the mechanical properties of thermal spray coatings: hardness testing and tensile adhesion testing. It discusses the destructive and non-destructive methods of residual-stress measurement. Electrochemical testing methodologies include two distinctly different methods: direct and alternating current impedance techniques for assessing the corrosion resistance of coating attributes. The article also reviews the testing methods for determining thermomechanical and environmental stability of thermal barrier coatings. It discusses the wear testing methodologies that are standardized by ASTM, including the pin-on-disk, block-on-ring, dry sand/rubber wheel, erosion, metallographic apparatus abrasion, fretting wear, cavitation, reciprocating ball-on-flat, impact, and rolling contact fatigue test. The article concludes with a discussion on the methods of testing abradability and erosion resistance in abradable coatings.

Corrosion monitoring is important in the operation of modern industrial plants and in the use and maintenance of expensive assets such as bridges and aircrafts, because the damage caused by corrosion and the rate of the deterioration can be huge and the risks devastating. This article discusses the system considerations and installation techniques of different types of direct and indirect techniques in electrochemically based on-line corrosion monitoring process. It describes the importance of probe location and on-line corrosion monitoring techniques with examples.

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.

Corrosion resulting from the presence and activities of microbes on metals and metal alloys is generally referred to as microbiologically influenced corrosion (MIC). This article describes the biofilm formation and structure and microbial processes influencing corrosion. It also discusses the electrochemical techniques used to study and monitor MIC and presents examples of their applications to MIC.

This article provides an overview of common analytical tools used as part of the process of providing practical information regarding the causes of a coating problem or failure. The common analytical tools include Fourier transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy-energy dispersive X-ray spectroscopy, chromatography, and electrochemical impedance spectroscopy. Test cabinets and standard test environments for laboratory analysis are reviewed. The article describes non-standard simulation testing and case studies of simulated environments for coating failure analysis.

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.

Electrode potential is a key parameter in the thermodynamic and kinetic processes that drive aqueous corrosion. This article discusses the complexities associated with measuring electrode potential and explains where and how to use reference electrodes to improve measurement accuracy. It describes a three-electrode approach that compensates for measurement error stemming from nonequilibrium conditions. It also examines electrode materials and behaviors and offers insights on selection and operating conditions.

This article presents common conventions and definitions in corrosion, electrochemical cells, cathodic protection (CP), electricity, and oxidation. Evans diagrams for impressed current CP in neutral or basic environment and galvanic or sacrificial CP, in both neutral or basic environment and acidic environment, are illustrated.

Principles of metallic corrosion play a fundamental role in developing industrial processes that employ corrosion for constructive purposes. This article examines the changes in kinetics that occur with differentially small potential changes around the equilibrium electrode potentials of two reversible electrodes, such as copper and silver electrodes, in an electrochemical system. It provides a schematic illustration of a reversible cell with copper and silver electrodes to determine a reversible cell potential between the electrodes. An electrode becomes irreversible when the electrode reactions are displaced from equilibrium and the electrode potential is no longer at the equilibrium potential. The article describes irreversible cell potential by using galvanic cells, electrolytic cells, and corrosion cells.