Showing papers on "Corrosion published in 1996"

Corrosion and electrochemistry of zinc

Abstract: Properties, Products, and Processes. Electrochemical Thermodynamics and Elemental Reactions. Passivation and Surface Film Formation. Semiconductor Electrochemistry of Zinc Oxide. Corrosion Potential and Corrosion Current. Corrosion Products. Corrosion Forms. Atmospheric Corrosion. Corrosion in Water and Aqueous Solutions. Corrosion in Soil. Under Paint Corrosion. Zinc Rich Coating. Corrosion in Concrete. Corrosion in Batteries. Corrosion in other Environments. Index.

Corrosion of Steel in Concrete: Understanding, investigation and repair

Abstract: Preface Acknowledgements Glossary Introduction Corrosion of steel in concrete: The corrosion process Black rust Pits, stray current and bacterial corrosion Electrochemistry, cells and half cells Conclusions Causes and mechanisms of corrosion and corrosion damage in concrete: Carbonation Chloride attack Corrosion damage Vertical cracks, horizontal cracks and corrosion The synergistic relationship between chloride attack, chloride binding and release Condition evaluation: Preliminary survey Detailed survey Available techniques Visual inspection Delamination Cover Half cell potential measurements Carbonated depth measurement Chloride determination Resistivity masurement Corrosion rate measurement Other useful tests for corrossion assessment Survey and assessment methodology Monitoring Special conditions: coated rebars and prestressing Physical and chemical repair and rehabilitation techniques: Concrete removal and surface preparation Patches Coating, sealers, membranes and barriers Encasement and overlays Sprayed concrete Corrosion inhibitors Electrochemical repair techniques: Basic principles of electrochemical techniques Cathodic protection The components of an impressed current cathodic protection system Cathodic protecton system design Control criteria System installation Cathodic protection of prestressed concrete Cothodic protection of epoxy coated reinforcing steel Cathodic protection of structures with ASR Chloride removal Realkalisation Comparison of techniques Rehabilitation methodology: Technical differences between repair options Repair costs Cabonation options Summary of options for carbonation repairs Chloride options Summary Understanding and calculating the corrosion of steel in concrete: Initiation time To, carbonation induced corrosion Chloride ingress rates (initiation) Rate of depassivation (activation) Deterioration and corrosive rates Corrosion without spalling Pitting corrosion Cracking and spalling rates, condition indices and end of functioning service life Summary of methodology to determine service life Building for durability: Cover, concrete and design Fusion bonded epoxy coated rebars Waterproofing membranes Penetrating sealers Galvinized rebar Stainless steel reinforcement Corrosion inhibitors Installing cathodic protestion in new structures Durable buildings Conclusions Future developments Appendix A: Bodies involved in corrosion and repair of reinforced concrete Appendix B: Stategic highway research program: published reports on concrete and structures (concrete and the corrosion of steel in atmospherically exposed reinforced concrere bridge componants suffering from chloride induced corrosion) Appendix C: Strategic highway research program: unpublished reports on concrete and structures (concrete and the corrosion of steel in atmospherically exposed reinforced concret

Overview: high-nitrogen alloying of stainless steels

Abstract: High-strength austenitic stainless steels can be produced by replacing carbon with nitrogen. Nitrogen has greater solid-solubility than carbon, is a strong austenite stabilizer, potent interstitial solid-solution strengthener, and improves pitting corrosion resistance. Although the solubility of nitrogen in liquid iron is very low, 0.045 wt.% at 1600 °C and atmospheric pressure, nitrogen levels above 1 wt.% can be obtained through alloying and specialized high-pressure melting techniques. An austenitic stainless steel should be considered “high-nitrogen” if it contains more nitrogen than can be retained in the material by processing at atmospheric pressure; for most alloys, this limit is approximately 0.4 wt.%. This article describes melting and processing technologies applicable to high-nitrogen steels and the effects of interstitial nitrogen on a variety of material properties. Thermal stability, nitride precipitation kinetics, and the effects of nitride formation on mechanical properties and corrosion resistance are discussed.

Deterioration of concrete due to reinforcement steel corrosion

Abstract: Steel corrosion in concrete leads to cracking, reduction of bond strength, reduction of steel cross section and loss of serviceability. Reinforced concrete undergoing corrosion does not only give the appearance of poor performance, but can in extreme cases, lose its structural integrity. Numerical relations to assess the loss of serviceability due to steel reinforcement corrosion are scanty, thus data to relate the rate of corrosion to cracking and loss of bond strength are necessary. This paper uses laboratory data to investigate the effects of corrosion rate on cracking and bond strength loss. It also examines the influence of fly ash on the rate of reinforcement corrosion. The laboratory data is used to develop numerical models to predict: 1. (a) rate of corrosion from the width and intensity of cracking 2. (b) bond stress from corrosion rate, and 3. (c) serviceability loss from corrosion rate.

An Electrochemical Model for Prediction of Corrosion of Mild Steel in Aqueous Carbon Dioxide Solutions

Abstract: A predictive model was developed for uniform carbon dioxide (CO2) corrosion, based on modeling of individual electrochemical reactions in a water-CO2 system. The model takes into account the electrochemical reactions of hydrogen ion (H+) reduction, carbonic acid (H2CO3) reduction, direct water reduction, oxygen reduction, and anodic dissolution of iron. The required electrochemical parameters (e.g., exchange current densities and Tafel slopes) for different reactions were determined from experiments conducted in glass cells. The corrosion process was monitored using polarization resistance, potentiodynamic sweep, electrochemical impedance, and weight-loss measurements. The model was calibrated for two mild steels over a range of parameters: temperature (t) = 20°C to 80°C, pH = 3 to 6, partial pressure of CO2 (PCO2) = 0 bar to 1 bar (0 kPa to 100 kPa), and ω = 0 rpm to 5,000 rpm (vp = 0 m/s to 2.5 m/s). The model was applicable for uniform corrosion with no protective films present. Performance of...

Sulfate‐reducing bacteria

Abstract: The corrosion of sewers and the control of odor are the major operational and maintenance problems in wastewater collection systems. The generation of hydrogen sulfide and subsequent sulfuric acid results from microbially mediated reactions, by sulfate‐reducing bacteria (SBR) and sulfide‐oxidizing bacteria. This review covers pertinent information about sulfate reduction‐induced problems in general and SBR in particular. Metabolism with respect to carbon, energy, and sulfur sources, ecology, growth factors (dissolved oxygen, temperature, pH, and sulfide), and the competitive effects of methane‐producing bacteria on SBR are discussed. Because metals react with sulfide to form metal sulfide precipitates with extremely low solubilities, metal interactions in sulfate reduction environments are discussed.

Microconstituent-Induced Pitting Corrosion in Aluminum Alloy 2024-T3

Abstract: Free corrosion immersion experiments were conducted on a commercial airframe material, Al 2024-T3 (UNS A92024), in 0.5 M sodium chloride (NaCl) solution to investigate the role of microcon...

Oxidation protection for carbon fibre composites

Abstract: Carbon fibre-reinforced ceramic matrix composites are promising candidate materials for high-temperature structural applications such as gas turbine blades. In oxidizing environments at temperatures above 400°C, however, carbon fibres are rapidly oxidized. There is, therefore, a need to coat the composite in order to protect it against oxidation. This review identifies the requirements of an effective oxidation protection system for carbon fibre-reinforced ceramics and summarizes the work which has been carried out towards this goal over the last 50 years. The most promising coatings are those composed of several ceramic layers designed to protect against erosion, spallation and corrosion, in addition to possessing a self-healing capability by the formation of glassy phases on exposure to oxygen.

Organic Inhibitors of Corrosion of Metals

Abstract: Electrochemical Aspects of the Inhibition of Corrosion Metals. The Role of the Chemical Composition of the Medium in the Protection of Metals from Corrosion. The Effect of Organic Compounds on the Initial Stages of the Localized Corrosion Metals. Corrosion Inhibitors Based on Complexing Agents. Organic Corrosion Inhibitors in Cooling Systems. Protection of Metallic Components during Their Assembly and Transport. Index.

Studies of the Formation of Cerium‐Rich Protective Films Using X‐Ray Absorption Near‐Edge Spectroscopy and Rotating Disk Electrode Methods

Abstract: The deposition of cerium-rich films on copper under cathodic polarization was studied as a model system for understanding the mechanism of corrosion inhibition of copper-containing aluminum alloys. Deposition was also studied on gold and iron for comparison with copper. Inhibition of corrosion of the aluminum alloys is achieved by deposition of a cerium-rich film on the copper-containing intermetallics that blocks the cathodic reduction of oxygen at these sites. X-ray absorption near-edge structure measurements show that cerium-rich films precipitated from aerated solutions are in the tetravalent state. Thermodynamically, the Pourbaix diagram predicts that under these conditions cerium should be in the trivalent state. This indicates that cerium chemistry is determined by processes in the solution rather than the potential of the electrode. Cerium-rich film formation is dependent on reduction of oxygen which influences the oxidation of Ce(III) to Ce(IV) in solution and precipitation of the film by changing the local pH at the electrode. The generation of hydrogen peroxide by oxygen reduction is considered to enhance cerium-rich film formation by oxidizing Ce(III) to Ce(IV) in solution. This was confirmed by addition of hydrogen peroxide to the solution.

Distribution of cobalt chromium wear and corrosion products and biologic reactions.

Abstract: Replacement hip arthroplasty with the use of ultrahigh molecular weight polyethylene for the cup articulating with a metal head has provided a low friction arthroplasty with years of success. However, the search for improved materials and designs for articulating surfaces continues. The use of metallic heads articulating with metallic cups is now being reconsidered for total hip replacements. Success will be enhanced if wear and corrosion of the articulating surfaces can be kept below that of the metal on ultrahigh molecular weight polyethylene couple. Concern has been raised about the release, and biologic fate, of metal species from corrosion and wear. Titanium alloys have been shown to have limitations as an articulating surface showing significant wear, and the alloy per se should not be considered for wear couples in total hip replacements. The cobalt chromium alloys are known to have reasonable wear and corrosion properties and continue to be evaluated. The issue of cobalt chromium wear and corrosion products and how this relates to the biologic performance of total hip replacement devices is reviewed. Under the condition of wear as currently experienced at the articulating surfaces of cobalt chromium alloys and ultrahigh molecular weight polyethylene, the amount of metallic products transferred to the tissues is sufficiently low to be well tolerated by the biologic system. Nickel and cobalt ions arc, rapidly transported from the implant site and eliminated in the urine. Chromium is stored in the tissue and eliminated more slowly. The issue of host hypersensitivity to these elements remains of concern. All 3 elements, in ionic form, are known to cause contact dermatitis. Untoward biologic reactions, including hypersensitivity, should be minimized if wear and corrosion phenomena are minimized.

Nickel Free High Nitrogen Austenitic Steels

Abstract: The paper presents the philosophy of the development and the resulting properties of a new austenitic stainless steel. The steel contains 15-18% chromium, 3-6% molybdenum, 10-12% manganese, and about 0.9% nitrogen. The most important feature of this steel is the complete absence of nickel as alloying element. The austenitic microstructure is obtained exclusively by adding nitrogen. Besides being nickel free, the steel is further characterized by an excellent corrosion resistance, the absence of ferromagnetism, and outstanding mechanical properties. The unique combination of these properties makes this steel most interesting for its use in items which are in direct contact with the human body. By using these new steels, nickel allergy can be prevented.

Self-Assembled Monolayer Mechanism for Corrosion Inhibition of Iron by Imidazolines

Abstract: Some of the most effective corrosion inhibitors for oil field pipeline applications are the oleic imidazoline (OI) class of molecules. However, the mechanism by which OIs inhibit corrosion is not known. We report atomistic simulations (quantum mechanics and molecular dynamics) designed to elucidate this mechanism. These studies lead to the self-assembled monolayer (SAM) model for corrosion inhibition, which explains the differences in corrosion inhibition efficiency for various OI molecules. The SAM model of OI inhibitors involves the following critical elements: (i) The function of the OI is to form a self-assembled monolayer on the native oxide surface of iron; this serves a protective role by forming a hydrophobic barrier preventing migration of H2O, O2, and electrons to the Fe surface. (ii) The imidazoline head group serves as a sufficiently strong Lewis base to displace H2O from the Lewis acid sites of the iron oxide surface. (iii) These head groups self-assemble on the surface to form an ordered mo...

Quantitative Prediction of Environmentally Assisted Cracking

Abstract: It has long been recognized that the stress corrosion cracking (SCC) and corrosion fatigue cracking susceptibility of various alloy and environment systems is dependent upon complex interactions between stress, material, and environmental parameters. This complexity can lead to scatter in cracking responses that, in turn, leads to difficulty in predicting the life of engineering structures. F.P. Ford was the 1995 recipient of the W.R. Whitney Award sponsored by NACE International. The present work is taken from his award lecture at CORROSION/95 held in March 1995 in Orlando, Florida. His lecture focused on how these interactions may be predicted quantitatively for ductile alloys in aqueous environments with knowledge of the cracking mechanism. This capability may lead to life prediction of critical structures in, for instance, boiling-water nuclear reactors (BWR).

Transition from pitting to fatigue crack growth—modeling of corrosion fatigue crack nucleation in a 2024-T3 aluminum alloy

Abstract: The nucleation of fatigue cracks from corrosion pits was investigated by conducting fatigue experiments on open-hole specimens of a 2024-T3 aluminum (bare) alloy in 0.5 M NaCl solution at room temperature and different load frequencies from 0.1 to 20 Hz. The maximum cyclic stresses applied at the hole ranged from 144 to 288 MPa and the load ratio, R , was 0.1. A specimen subjected to pre-corrosion in the NaCl solution prior to corrosion fatigue was also investigated. Pitting was found to be associated with constituent particles in the hole and pit growth often involved coalescence of individual particle-nucleated pits. Fatigue cracks typically nucleated from one or two of the larger pits, and the size of the pit at which the fatigue crack nucleates is a function of stress level and load frequency. The observations indicate that the nucleation of corrosion fatigue cracks essentially results from a competition between the processes of pitting and crack growth. Pitting predominates in the early stage of the corrosion fatigue process, and is replaced by corrosion fatigue crack growth. Based on these results, two criteria are proposed to describe the transition from pit growth to fatigue crack growth: (1) the stress intensity factor of the equivalent surface crack has to reach the threshold stress intensity factor, Δ K th , for fatigue crack growth, assuming that a corrosion pit may be modeled by an equivalent semi-elliptical surface crack, and (2) the time-based corrosion fatigue crack growth rate also exceeds the pit growth rate.

Modeling the Time-to Corrosion Cracking of the Cover Concrete in Chloride Contaminated Reinforced Concrete Structures

Abstract: ii Acknowledgments iii List of Figures vii List of Tables x Notations xi 1.0 Introduction 1 1.1 Background 1 1.2 Deterioration Models 1 1.3 Scope of Study 3 2.0 Review of Corrosion of Steel in Concrete 2.1 Background 5 2.1.1 Mechanism of Electrochemical Corrosion 5 2.1.2 Pourbaix Diagrams 7 2.1.3 Polarization 8 2.1.4 Passivity 11 2.1.5 Growth of Rust Film 11 2.2 Corrosion of Steel in Concrete 12 2.2.1 Concrete as an Electrolyte 12 2.2.2 Principles of Steel Corrosion in Concrete 16 2.2.3 Initiation of Steel Corrosion in Concrete 19 2.2.4 Corrosive Activity of Concrete 21 2.3 Corrosion Monitoring Techniques 25 2.3.1 Half-cell Potential 25 2.3.2 Linear Polarization Technique 26 2.3.3 AC Impedance 28 2.3.4 Gravimetric Technique (Weight Loss Method) 28 2.3.5 Techniques for Determining the Chloride Content 29 2.4 Summary 29 3.0 Review of Time to Cracking Models 32 3.1 Cady-Weyers' Deterioration Model 32 3.2 Bazant’s Mathematical Models of Time to Cracking 32 3.3 Morinaga’s Empirical Equation of Time to Cracking 34 3.4 Other Metal Loss Criteria to Cracking 35 3.5 Some Comments on Existing Model s 36

Corrosion resistance and corrosion fatigue strength of new titanium alloys for medical implants without V and Al

Abstract: The corrosion resistance and the corrosion fatigue strength of Ti-15Zr-4Nb-4Ta-0.2Pd-0.2O-0.05N and Ti-15Sn-4Nb-2Ta-0.2Pd-0.2O alloys were compared with those of Ti-6Al-4 V extra low interstitial (ELI), Ti-6Al-2Nb-1Ta, pure Ti grade 2 and β type Ti-15%Mo-5Zr-3Al alloys. Anodic polarization and corrosion fatigue testings were performed in various physiological saline solutions at 310 K. The corrosion fatigue test was carried out under the condition of a tension to tension mode with a sine wave at a stress ratio of 0.1 and at a frequency of 10 Hz. The tensile properties of these alloys were measured at room temperature. The change in current density was small up to passivity zone in 1 wt.% lactic acid, PBS(−), calf serum and eagle's MEM + fetal bovine serum solutions except 5 wt.% HCl. The current density of Ti-15Zr-4Nb-4Ta-0.2Pd-0.2O-0.05N alloy at potential up to 5 volt tend to be lower than that of Ti-6Al-4V ELI. Otherwise passive current density of the β type Ti-15Mo-SZr-3Al alloy was higher than that of α + β type alloys. The passive films formed on Ti-15Zr-4Nb-4Ta-0.2Pd-0.2O alloy in the calf serum consisted mainly of TiO2, ZrO2, Nb2O5, Ta2O5 and Pd or PdO as demonstrated using X-ray photoelectron spectroscopy. The cycle to failure of Ti-15Zr-4Nb-4Ta-0.2Pd-0.2O-0.05N and Ti-15Sn-4Nb-4Ta-0.2Pd-0.2O alloys annealed at 973 K for 7.2 ks increased with decreasing applied maximum stress. The fatigue strength at 108 cycles in those alloys was about 600 MPa. The fatigue strength of Ti-6Al-2Nb-1Ta alloy at 108 cycles was about 700 MPa. The fatigue strength of β type Ti-15Mo-5Zr-3Al alloy at 107 cycles was lower than that of α + β type alloys.

Novel thermodynamically stable and oxidation resistant superhard coating materials

Abstract: A theoretical concept for the design of novel, nanocrystalline and thermodynamically stable materials with hardness of ≥50 GPa (about 5000 kg mm−2), elastic modulus of ≥500 GPa and a high stability against oxidation in air up to 800°C is described together with its experimental verification on several systems nc-MexN/a-Si3N4 (Me  Ti, W, V). The concept is based on avoiding the formation and multiplication of dislocations in the nanocrystalline phase, and blocking the crack propagation in a 0.3–0.5 nm thin amorphous tissue. The theoretical principles of the design of such materials and the thermodynamic criteria for the segregation of the nc- and a-phases, which is necessary for the preparation of such materials, are discussed. Several micron thick films of such materials have been prepared by plasma CVD at a rate of 0.6–1 nm s−1 from the corresponding metal halides, hydrogen, nitrogen and silane at deposition temperatures of ≤550°C. A low content of chlorine of ≤0.3 at.% assures their stability against corrosion in air. Upon microindentation up to a load of ≥100 mN the films show a remarkably high elastic recovery of about 80%. Unlike diamond, c-BN, and C3N4 these materials are thermodynamically stable and relatively easy to prepare.