Showing papers on "Corrosion published in 1999"

Corrosion mechanisms of magnesium alloys

Abstract: The high strength to weight ratio of magnesium alloys makes them extremely attractive for applications in transport or aerospace technology. However, their corrosion behavior is a major issue and one reason why they are still not as popular as aluminum alloys. This papers reviews the corrosion mechanisms of magnesium and provides the basis for the design of new alloys with improved corrosion properties.

Handbook of Corrosion Engineering

Abstract: Introduction 1. Aqueous Corrosion 2. Environments and Application Examples 3. high-Temperature Corrosion 4. Modeling, Life Prediction, and Computer Applications 5. Corrosion Failures 6. Corrosion Maintenance Through Inspection And Monitoring 7. Acceleration and Amplification of Corrosion Damage 8. Materials Selection 9. Protective Coatings 10. Corrosion Inhibitors 11. Cathodic Protection 12. Anodic Protection

Corrosion of Aluminum and Aluminum Alloys

Abstract: This volume presents comprehensive coverage of the corrosion behavior of aluminum and aluminum alloys, with emphasis on practical information about how to select and process these materials in order to prevent corrosion attack Described are the characteristics of these materials and the influences of composition, mechanical working, heat treatment, joining methods, microstructure, and environmental variables on their corrosion

Melt corrosion of oxide and oxide–carbon refractories

Abstract: Penetration and dissolution mechanisms are reviewed for predominantly single phase oxide, two phase oxide, and oxide–carbon composite refractories by liquid silicates. Theoretical models of these processes, as well as static (sessile drop, dipping, and crucible) and dynamic (rotating finger and rotary slag) experimental tests, along with their practical limitations are considered. Direct (congruent or homogeneous) attack involves dissolution of a solid into a liquid with no intermediate solid phase leading to active corrosion. Indirect (incongruent or heterogeneous) attack leads to formation of one or more new solid phases at the original solid/liquid interface. This may lead to passive corrosion. Examples of direct and indirect attack in a range of refractory–liquid systems are described highlighting the critical influence of the composition and hence viscosity of the local liquid adjacent to the solid. Penetration and corrosion can be controlled either through the local liquid composition via th...

Effect of Fluoride Concentration and pH on Corrosion Behavior of Titanium for Dental Use

Abstract: Titanium is used as a metal for biocompatible materials such as dental implants or restorations because of its excellent chemical stability. However, the corrosion of Ti in the prophylactic fluoride-containing environment can become problematic. To clarify the effects of fluoride concentration and pH on the corrosion behavior of Ti, we conducted anodic polarization and immersion tests in NaF solution of various concentrations and pH values. The concentrations of dissolved Ti in the test solutions were analyzed by inductively coupled plasma mass spectroscopy. There were obvious limits of fluoride concentration and the pH value at which the corrosion behavior of Ti changed. The corrosion of Ti in the solution containing fluoride depended on the concentration of hydrofluoric acid (HF). When the HF concentration in the solution was higher than about 30 ppm, the passivation film of the Ti was destroyed. The results of this study revealed a relation between the fluoride concentrations and pH values at which Ti corrosion occurred and provided data on such corrosion in environments where the fluoride concentration and pH value are known.

Corrosion Behavior of Carbon Steel in the CO2 Absorption Process Using Aqueous Amine Solutions

Abstract: The present study provides comprehensive information on the effects of process parameter variations on the corrosion behavior of carbon steel in CO2 absorption systems using aqueous amine solutions. The process parameters of interest are amine type, concentration of the amine solutions, solution temperature, CO2 loading, and oxygen content. An electrochemical testing technique was used for determining the system corrosiveness in terms of polarization behavior and corrosion rate. The experimental results suggest that the corrosion behavior is considerably sensitive to the variations in the process parameters. Increases in amine concentration, solution temperature, CO2 loading, and oxygen content accelerate the corrosion rate in the systems. In addition, different amine types yield different degrees of the system corrosiveness. Comparisons of the corrosiveness among single amine systems as well as between mixed amine systems and their precursors are also presented.

4-Aminoantipyrine as an inhibitor of mild steel corrosion in HCl solution

Abstract: 4-aminoantipyrine (AAP) was tested as a corrosion inhibitor for mild steel in 2 M HCl solution using different techniques: weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that AAP is an inhibitor for mild steel in this medium. The inhibition was assumed to occur via adsorption of the inhibitor molecule on the metal surface. In the 20 to 60 ∘C temperature range, the AAP adsorption follows the Flory–Huggins isotherm and/or the El-Awady et al. kinetic-thermodynamic model. The protection efficiency increases with increasing inhibitor concentration (in the range 10−310−2 M) but decreases with increasing temperature. The thermodynamic functions of dissolution and adsorption processes were calculated.

Development of a Structure‐Activity Relationship for Oil Field Corrosion Inhibitors

Abstract: Corrosion rate data for mild steel corrosion inhibitors in carbonated brine media were fitted to the Temkin adsorption isotherm. The fundamental constants of the Temkin adsorption isotherm, i.e., molecular interaction and adsorption equilibrium constants, were used to glean important information about the behavior of adsorbed corrosion inhibitors. Adsorption data were also used to calculate , , and , and the results demonstrated that some compounds are chemisorbed onto the electrode. Significantly, it has been found that chemisorption of corrosion inhibitors can yield very good film persistency (i.e.. corrosion protection even when the inhibitor is no longer present). Molecular modeling using the quantum mechanical program PCSpartan plus, along with a comparative analysis of adsorption data for a broad range of inhibitor molecules, has been used to derive a tentative structure/activity relationship for some oil field corrosion inhibitors. © 1999 The Electrochemical Society. All rights reserved.

Flexural Strength of Concrete Beams with Corroding Reinforcement

Abstract: The paper presents the results of an experimental study on 111 under-reinforced concrete beams to determine their residual flexural capacity after undergoing different degrees of reinforcement corrosion. Corrosion was induced in the laboratory by an accelerated corrosion technique using two sources of external power supply. The beams were precured for different periods of up to I year before accelerated corrosion was induced in the reinforcement. Different degrees of reinforcing bar corrosion were induced in increments, ranging from 1.25 to 10 percent at corrosion rates off, 2, 3, and 4 mA/cm(2). The beams were reinforced with two longitudinal bars. Shear reinforcement was provided by external means using steel collars. The results show marked reductions in flexural strength due to reinforcement corrosion, which is caused primarily by the breakdown of bond at the steel/concrete interface.

A Mechanistic Investigation of Polyaniline Corrosion Protection Using the Scanning Reference Electrode Technique

Abstract: Growing environmental concerns regarding the use of heavy metals in coating formulations have lead to a new coating strategy employing inherently conducting polymers (ICPs), such as polyaniline (PANI), as a key component. The principal potential advantage offered by the ICP coating technology is toleration of pinholes and minor scratches. This paper describes the application of the scanning reference electrode technique (SRET) to the study of PANI coatings on carbon steel. SRET results demonstrate that conductive PANI passivates pinhole defects in coatings on carbon steel. In addition, it is shown that phosphonic acid salts of PANI are more effective for corrosion protection than sulfonic acid salts. A model is proposed which entails passivation of the metal surface through anodization of the metal by PANI and formation of an insoluble iron-dopant salt at the metal surface.

PVD coatings as an environmentally clean alternative to electroplating and electroless processes

Abstract: Today the development of clean technologies in all spheres of industrial manufacturing is an essential task, not only for material and metal finishing but also for plasma surface engineering. Among the most critical group of technologies which needs to be replaced by alternative technologies are processes used to produce functional galvanic and decorative coatings. The electroplating of finishes, such as hard chromium, cadmium and nickel in metal finishing is today recognized as a major source of environmental pollution in every country. Therefore wet bath technologies have started to lose favour compared with high performance dry coating methods such as physical vapour deposition (PVD), plasma-assisted chemical vapour deposition, chemical vapour deposition and thermal spraying. Among these techniques, the results obtained with PVD coatings in metal cutting and forming in the last 15 years show the most promising solution of the complicated situation in which galvanic coatings seemed to be technologically and economically irreplaceable. In this paper the general situation in this field is shown. Already today it is possible to replace efficiently some of the galvanic processes in specific cases (e.g. Cr, Ni, Cd, Zn, Au). It is important to point out that PVD is considered to be a technique which can provide not only metallic, but also alloyed and ceramic coatings with a virtually unlimited range of chemical composition and therefore controlled protective, mechanical and wear-resistant properties. Entering into competition with galvanic coatings the manufacturers of PVD coaters were confronted with new requirements: a huge quantity of substrates of the same size, to be chemically and plasma cleaned and then coated at the highest possible deposition rate. For industrial mass production one can therefore use only large PVD batch systems or in-line coaters. The alternative for today's low price galvanic coatings is therefore dry and clean PVD technologies, fully supported by legislation on environmental protection. The economics depend directly on the substrate type and the quantity. The first positive results on the replacement of electrodeposited nickel on aluminium substrates and hard chrome on soft iron are also reported here. A soldering test was made on a sputtered nickel layer. Wear and corrosion tests were performed with iron cores, coated with PVD CrN coating. All tests were made in the Slovenian automotive industry. Results show that for a large number of substrates PVD clean technology is already economically competitive with galvanic coatings.

Review of naphthenic acid corrosion in oilrefining

Abstract: Naphthenic acid corrosion is a major concern for the oil refinery business. While much is now known about the phenomenon, it is still not completely understood because of the complex influences on corrosion of the type of acid and other constituents in the crude oil and the effects of both temperature and fluid flow. A review of this form of corrosion has been undertaken with respect to the role of crude oil composition, temperature, fluid velocity, physical state (vapour or liquid), pressure, and materials of construction. Simple measures of corrosivity based on the total acid or neutralisation number are insufficient. The sulphur content of the crude is important but the extent to which the various sulphur containing compounds act as inhibitors or corrodents is not understood. There is little knowledge also of the nature of films formed on the steel surfaces under operating conditions and the role of natural inhibitors that may be present in crudes requires more attention.

Electrochemical Studies of the Adsorption Behavior of Bovine Serum Albumin on Stainless Steel

Abstract: The adsorption behavior of bovine serum albumin (BSA) on high-purity austenitic low-carbon stainless steel and its effect on the state of the electrode surface have been studied over the temperature range 299−343 K under open-circuit-potential conditions, using electrochemical impedance spectroscopy (EIS). The impedance spectra were interpreted in terms of an equivalent electrical circuit (EEC) based on a possible physical model with the circuit elements representing the electrochemical properties of the investigated system. The adsorption of BSA onto the stainless steel surface resulted in an increased rate of metal dissolution, i.e., corrosion. The plateau values of corrosion rate were achieved after a “threshold” BSA concentration in the bulk solution at all the temperatures studied. The rate of the corrosion process was found to be controlled by both the surface diffusion and charge transfer process. Adsorption of BSA onto the stainless steel surface was described with a Langmuir adsorption isotherm. ...