Corrosive Environmental Conditions Research Articles

Experimental observations of self-consolidated hybrid fiber reinforced concrete (SC-HyFRC) on corrosion damage reduction

Correlations between the rate of corrosion damage in reinforced concrete and observable cracking have been established by a multitude of design codes. Based on this relationship, it is inferred that cracking prevention may provide a suitable corrosion protection scheme capable of enhancing the durability/life expectancy of reinforced concrete exposed to potentially corrosive environmental conditions. A self-consolidated hybrid fiber reinforced concrete mixture is tested under a chloride-induced corrosive environment to determine the role of crack suppression in both the initiation and the propagation phases of corrosion damage. It is observed that in the presence of the hybrid fiber reinforcement, chloride migration rates are not significantly altered by the introduction of moderate cyclical mechanical loading in contrast to conventional concrete samples. Furthermore, the accumulation of damage in the propagation phase of reinforcement corrosion is significantly altered by the suppression of splitting cracks emanating radially outward from the reinforcing bar surface. While not a corrosion elimination scheme, the incorporation of hybrid fiber reinforcement is nonetheless capable of prolonging the life expectancy of a given reinforced concrete element and providing an increased measure of durability.

High Volume Production Technology for Corrosive Resistant Long-Fiber-Reinforced Plastic Extinguishers

Portable fire extinguishers need to be reliable and fully functional at all given environmental conditions. Especially in off-shore and power plant applications a specific range of properties is necessary, e.g. corrosive resistance and electromagnetic compatibility. Hence, the application of fiber reinforced composites and fiber composite design offers an alternative to the traditional application of metallic materials.Within the scope of the development of an innovative fire extinguisher, a process-chain for manufacturing of composite fire extinguishers suitable for aggressively corrosive environmental conditions was developed. The aim of the project has been the development of a fire extinguisher with the technology of thermoplastic composite materials. Besides the intended weight reduction, a concept for the realization of a high-volume production suitable process-chain had to be developed. Using a thermoplastic matrix material allows a corrosive-free, non-magnetic and functional integrated design. Within the scope of the research project, the extinguisher container with integrated base and connection for the valve has been dimensioned and designed. The containers geometry with optimized ratio of filling volume, overall part size and material utilization was derived by applying FE analysis. Furthermore, a process-chain for high-volume production was conceived and had been verified by producing functional demonstrators for further testing.The container is made of two glass-fiber reinforced injection molding parts being thermally joined. The leakproofness and sufficient material strength after the joining process were identified as key challenges of the joining process and were overcome with an adapted design of the molded parts. Within the process development, reproducible and high quality weld joints were achieved based on a robust and cost-efficient joining technology. For reliable processing, the specific processing parameters were analyzed and regulations for each processing step deduced.

Mechanisms of hydrogen‐induced cracking in high‐strength screws

Low alloyed high strength steels with yield strength above 1200 MPa are increasingly implemented for the reduction of the component weight in the automotive industry. This material type is known for its susceptibility to hydrogen assisted cracking. Both, manufacturing process induced and hydrogen induced embrittlement during component operation have to be considered. The aim of this study was to evaluate the impact of different zinc‐containing topcoats on hydrogen re‐embrittlement. The susceptibility of high strength fasteners (strength class 12.9) with various zinc‐based topcoats (electroplated zinc, electroplated zinc‐nickel, galvanized zinc and zinc‐flake) were tested under various corrosive environmental conditions. It is shown that the zinc‐containing topcoats impose a different susceptibility on hydrogen re‐embrittlement. Under the tested environmental conditions, fasteners with electroplated zinc revealed a decrease in the fracture load compared to the heat treated black specimen. In contrast to that, an electroplated zinc‐nickel topcoat demonstrated a failure at the loads slightly exceeding the fracture load of the uncoated specimen.

Rolling‐sliding, scuffing and tribocorrosion behaviour of PVD multilayer coatings for gears application

PurposeThe aim of this work is the study the tribological behaviour and tribocorrosion resistance of newly developed multilayer PVD coatings Cr/CrN and CrN/ZrCN applied on nitrided F1272 steel for gear applications.Design/methodology/approachTribological characterization has been completed by several tribological tests performed under ball‐on‐disc configuration, extreme pressure tests to determine the maximum load before the films failure and rolling‐sliding tests under line‐contact conditions (35‐40 per cent of sliding). The response of the different coatings to sodium chloride aggressive environment has been simulated by accelerated tribocorrosion tests, combining simultaneously chemical and mechanical factors. The synergistic effect of wear on corrosion behaviour and vice versa, has been studied in order to compare the protective properties of the different PVD coatings developed.FindingsCr/CrN PVD coating improves wear in almost a 90 per cent compared to the nitrided substrate, presenting a similar behaviour to this one under extreme pressure conditions. CrN/ZrCN coating also improved substrate wear and especially good behaviour for this coating was observed under extreme pressure conditions. Cr/CrN coating strongly decreases micropitting and scuffing effect when it is tested under rolling‐sliding configuration. Under micro‐pitting conditions, coating protects the substrate and reduces the fatigue of uncoated discs. When adhesive wear (scuffing) is studied also Cr/CrN improves notable the nitrided steel performance. Under simultaneously corrosion‐wear conditions, Cr/CrN coating registered the lowest material loss because in this case only corrosion effect contributed to the coated surface degradation being the mechanical contribution inappreciable.Originality/valueNew multilayer coatings with improved wear performance and tribocorrosion resistance have been developed and comprehensively characterized. These coatings can be used in advanced gears for corrosive environmental conditions as well as with biodegradable lubricants.

Comparative analysis of various corrosive environmental conditions for NiTi rotary files

The aim of the present study is to compare the corrosion tendency using two kinds of NiTi files in the various environmental conditions through the visual examination and electrochemical analysis. ProTaper Universal S2, 21 ㎜ (Dentsply Maillefer, Ballaigues, Switzerland) and Hero 642, 0.06 tapers, size 25, 21 ㎜ (Micromega, Besancon, France) rotary instruments were tested. The instruments were randomly divided into eighteen groups (n = 5) by the immersion temperature, the type of solution, the brand of NiTi rotary instrument and the presence of mechanical loading. Each file was examined at various magnifications using Scanning Electron Microscope (JEOL, Akishima, Tokyo, Japan) equipped with energy dispersive X-ray microanalysis (EDX). EDX was used to determine the components of the endodontic file alloy in corroded and noncorroded areas. The corrosion resistance of unused and used NiTi files after repeated uses in the human teeth was evaluated electrochemically by potentiodynamic polarization test using a potentiostat (Applied Corrosion Monitoring, Cark-in-Cartmel, UK). Solution temperature and chloride ion concentration may affect on passivity of NiTi files. Under the conditions of this in vitro study, the corrosion resistance is slightly increased after clinical use.

Nondestructive Evaluation of RC Structures Strengthened with FRP Laminates Containing Near-Surface Defects in the form of Delaminations

Fiber reinforced polymer (FRP) composites are being utilized in a wide range of application areas in structural rehabilitations because these materials are less affected by corrosive environmental conditions and known to provide longer life with less maintenance. However, there are still some concerns about FRP strengthened reinforced concrete (RC) structures, such as the presence of near-surface defects. Currently limited data exists regarding this issue. The presence of near-surface defects in the form of delaminations between the fiber reinforced polymer (FRP) laminate and concrete substrate can significantly affect the structural integrity and stiffness of the structural section. These defects should be properly detected and accurately located to access if injection or replacement is warranted. The control and assessment of these defects still require improvements in detection techniques and standardization in these assessment methods. The latest advances in non-destructive evaluation (NDE) techniques including technologies in microwave, acousto-ultrasonic, impact-echo and thermography are providing promising results in detecting such defects and are discussed in further detail in this paper. 1 Senior Evaluation Specialist, International Code Council-Evaluation Service, 5360 Workman Mill Road, Whittier, California, 90601 mekenel@icc-es.org (Corresponding Author) 2 Associate Professor, Department of Civil, Arch. & Env. Engineering, University of Missouri-Rolla, Rolla, Missouri, 65401 jmyers@umr.edu Ekenel, M. and Myers, J.J. 2

Performance Evaluation of Carbon Fiber-Reinforced Polymer-Repaired Beams Under Corrosive Environmental Conditions

This paper presents results of an experimental study designed to evaluate the performance of reinforced concrete beams repaired with carbon fiber reinforced polymer (CFRP) sheets under corrosive environmental conditions. A total of 16 beams, 152 x 254 x 3200 mm each, were tested. One beam was used as a control while 15 beams were initially corroded electrochemically for 50 days that corresponded to approximately 9% steel mass loss. Following the initial corrosion, one beam was tested to failure while 14 beams were repaired with a flexural CFRP sheet along with a continuous wrapping or an intermittent wrapping. Following repair, two repaired beams were tested to failure while 12 beams were subjected to additional corrosion exposure for up to 310 days that corresponded to a maximum steel mass loss of approximately 34%. Six beams were exposed to additional corrosion under a sustained load to simulate a service condition. Test results showed that the beams of intermittent wrapping had a higher steel mass loss rate and thus a lower strength than the beams of continuous wrapping. The presence of the sustained load and associated flexural cracks during the post-repair corrosion exposure slightly increased the steel mass loss rate, which further reduced the beam yield load but it had no noticeable effect on the beam ultimate strength.

Comparative Corrosion and Current Burst Testing of Copper and Aluminum Electrical Power Connectors

Crimped and mechanically bolted aluminum and copper connectors are commonly used for terminating industrial electrical power cables with ratings up to 600 V. Aluminum connectors are available for use with aluminum or copper conductor, and copper connectors are available for use with copper conductor only. The performance of copper and aluminum connectors was compared by conducting accelerated aging under corrosive environmental conditions. The testing consisted of 2000 hours of cyclic salt fog environmental exposure, in conjunction with periodic electrical current burst testing. The connectors were evaluated by comparing the change in resistance of the test samples as the test progressed.

New experience in field of application of corrosion resistance protection in flue gas desulphurisation plant absorbers

AbstractAbsorbers form the main part of the flue gas desulphurisation plants for 360 MW units at the Belchatow Power Station in Poland. The plant working cycle and service life are dependent on the grades of the corrosion resistance, protection materials used as an absorber lining in individual zones. The objective of manufacturers activities in this field has been to extend the service life of the flue gas desulphurisation plant. This has been implemented by testing 'wallpapering' technology in the absorber cylindrical part, using plate sheets of Hastelloy nickel alloys, 0·5 to 1·6 mm in diameter. Experiments involving Hastelloy nickel alloys, grades C-22 and C-2000, among others, were used to evaluation the resistance of the base material, 'wallpaper' plate sheet, welded joints and heat affected zones (HAZ) towards corrosion. The corrosion tests were executed for three different conditions of corrosive environment: (a) actual boiler outlet environment: chemical composition of boiler outlet flue gases, w...

Sensors to Monitor CFRP/Concrete Bond in Beams Using Electrochemical Impedance Spectroscopy

The use of inexpensive electrochemical impedance spectroscopy based sensor technology for nondestructive evaluation (NDE) of bond degradation between external carbon fiber-reinforced polymer (CFRP) reinforcement and concrete is examined. Copper tape on the surface of the CFRP sheet, stainless steel wire embedded in the concrete, and reinforcing bars were used as the sensing elements. Laboratory experiments were designed to test the capability of the sensors to detect the debonding of the CFRP from the concrete and to study the effect of short-term (humidity and temperature fluctuations) and long-term (freeze-thaw and wet-dry exposure and rebar corrosion) environmental conditions on the measurements. The CFRP sheet was debonded from the concrete, and impedance measurements were taken between various pairs of electrodes at various interfacial crack lengths. The dependence of the impedance spectra, and of the parameters obtained from equivalent circuit analysis, on the interfacial crack length was studied. Capacitance parameters in the equivalent circuit correlated strongly with the interfacial crack length and can be used to assess the global state of the bond between CFRP sheets and concrete. Impedance measurements taken between embedded wire sensors can be used to detect the location of debonded regions.

Acousto-Ultrasonic Technology for Nondestructive Evaluation of Concrete Bridge Members Strengthened by Carbon Fiber-Reinforced Polymer

Carbon fiber-reinforced polymer (CFRP) composites have been used in a wide range of application areas in bridge rehabilitations because these materials are less affected by corrosive environmental conditions, are known to provide longer life, and require less maintenance. However, the quality control and quality assessment of these new rehabilitation systems should be further improved and standardized. A recent rehabilitation project that used CFRP laminates was done on a bridge in Dallas County, Missouri, by the Missouri Department of Transportation and the Center for Infrastructure Engineering Studies at the University of Missouri-Rolla. The acousto-ultrasonic nondestructive testing technology was performed to detect and image surface defects in the form of delaminations. These were intentionally formed at the CFRP sheet-concrete interface to investigate the ability of this technique. Acousto-ultrasonic nondestructive testing has shown the ability to detect and image the delaminations between CFRP sheet...

Acousto-Ultrasonic Technology for Nondestructive Evaluation of Concrete Bridge Members Strengthened by Carbon Fiber–Reinforced Polymer

Carbon fiber–reinforced polymer (CFRP) composites have been used in a wide range of application areas in bridge rehabilitations because these materials are less affected by corrosive environmental conditions, are known to provide longer life, and require less maintenance. However, the quality control and quality assessment of these new rehabilitation systems should be further improved and standardized. A recent rehabilitation project that used CFRP laminates was done on a bridge in Dallas County, Missouri, by the Missouri Department of Transportation and the Center for Infrastructure Engineering Studies at the University of Missouri–Rolla. The acousto-ultrasonic nondestructive testing technology was performed to detect and image surface defects in the form of delaminations. These were intentionally formed at the CFRP sheet–concrete interface to investigate the ability of this technique. Acousto-ultrasonic nondestructive testing has shown the ability to detect and image the delaminations between CFRP sheet and concrete substrate.

A comparative analysis of the wear characteristics of glazes generated on the ordinary Portland cement surface of concrete by means of CO 2 and high power diode laser radiation

The wear characteristics of a glaze generated on the ordinary Portland cement (OPC) surface of concrete using a 2 kW high power diode laser (HPDL) and a 3 kW CO 2 laser have been determined. Within both normal and corrosive environmental conditions, the wear rate of the CO 2 and HPDL generated glazes were consistently higher than the untreated OPC surface of concrete. Life assessment testing revealed that surface glazing of the OPC with both the CO 2 and the HPDL effected an increase in wear life of 1.3–17.7 times over an untreated OPC surface, depending upon the corrosive environment. The reasons for these marked improvements in the wear resistance and wear life of the CO 2 and HPDL generated glazes over the untreated OPC surface of concrete can be attributed to the partial (CO 2 laser) and full (HPDL) vitrification of the OPC surface after laser treatment which subsequently created a much more dense and consolidated surface with improved microstructure and phase characteristics which is more resistant in corrosive environments. In addition, the wear life and the wear rate of the HPDL glaze was found to be consistently higher than that of the CO 2 laser glaze. This is due to the fact that CO 2 and HPDLs have very different wavelengths; consequently, differences exist between the CO 2 and HPDL beam absorption characteristics of the OPC. Such differences give rise to different cooling rates, solidification speeds, etc. and are, therefore, the cause of the distinct glaze characteristics which furnishing each microstructure with its own unique wear resistance characteristics.

Augmentation of the mechanical and chemical resistance characteristics of an Al 2O 3-based refractory by means of high power diode laser surface treatment

Augmentation of the wear rate and wear life characteristics of an Al 2O 3-based refractory within both normal and corrosive (NaOH and HNO 3) environmental conditions was effected by means of high power diode laser (HPDL) surface treatment. Life assessment testing revealed that the HPDL generated glaze increased the wear life of the Al 2O 3-based refractory by 1.27–13.44 times depending upon the environmental conditions. Such improvements are attributed to the fact that after laser treatment, the microstructure of the Al 2O 3-based refractory was altered from a porous, randomly ordered structure, to a much more dense and consolidated structure that contained fewer cracks and porosities. In a world economy that is increasingly placing more importance on material conservation, a technique of this kind for delaying the unavoidable erosion (wear) and corrosion that materials such as the Al 2O 3-based refractory must face may provide an economically attractive option for contemporary engineers.

Surface treatment of an Al 2O 3-based refractory with CO 2 and high power diode lasers for improved mechanical and chemical resistance characteristics

Within both normal and corrosive (NaOH and HNO 3) environmental conditions, the wear rate and wear life characteristics of an Al 2O 3-based refractory were greatly enhanced by means of CO 2 and high power diode laser (HPDL) surface treatment. Such improvements are attributed to the fact that after laser treatment, the microstructure of the Al 2O 3-based refractory was altered from a porous, randomly ordered structure, to a much more dense and consolidated structure that contained fewer cracks and porosities. What is more, resulting from the different rates of solidification brought about by differences in the wavelengths of the two lasers, dissimilar microstructures were subsequently generated. Indeed, despite the fact that the glaze thickness was less, the wear life of the HPDL treated surface exceeded that of the CO 2 laser treated surface in all the test environments owing to its finer, more densely packed and less cracked microstructure.

Modelling the tribo-corrosion interaction in aqueous sliding conditions

In corrosion wear, one of the most commonly observed phenomena is the synergism where both corrosion and wear are significantly increased by the tribo-corrosion interactions, leading to much greater material losses than produced by the sum of losses by either process alone. However, mechanisms for the synergistic effect are generally not well understood and there has been little effort in modelling synergistic processes. In this paper, mechanisms for the interactions between corrosion and sliding wear of metals are proposed and a mathematical model is developed which incorporates the various factors affecting corrosion wear, including experimental and environmental conditions and material properties. Many of the observed phenomena in corrosion wear can be explained. It also provides a good basis for wear map construction and would be especially useful in carrying out dimensional analyses for constructing such maps.

A comparative investigation of the wear characteristics of a high power diode laser generated single-stage and commercial epoxy tile grout

A comparative study of a single-stage ceramic tile grout, generated using a 60 W high power diode laser (HPDL), and a commercially available tile grout has determined the wear characteristics of the two materials. Within both normal and corrosive environmental conditions, the single-stage ceramic tile grout proved to have a superior wear rate over the epoxy tile grout, 0.9 mg/cm 2 h compared with 125 mg/cm 2 h, when in an HNO 3 environment. Likewise, life assessment testing revealed that the single-stage ceramic tile grout gave an increase in wear life of 4–42 times over the commercially available epoxy tile grout, depending upon the corrosive environment. It is believed that the economic and material benefits to be gained from the deployment of such an effective and efficient means of sealing ceramic tiles could be significant.

The wear characteristics of a high power diode laser generated glaze on the ordinary Portland cement surface of concrete

The ordinary Portland cement (OPC) surface layer of concrete, which was glazed using a high power diode laser (HPDL), has been tested in order to determine the wear characteristics of the glaze. The work showed that the generation of a surface glaze resulted in the considerable enhancement of the wear characteristics over an untreated OPC surface of concrete. Within both normal and corrosive (detergent, NaOH and HNO 3) environmental conditions the wear rate of the HPDL generated glaze was 3.5 mg cm −2 h −1. In contrast, the untreated OPC surface of concrete exhibited a wear rate of 9.8–114.8 mg cm −2 h −1 when exposed to the various reagents. Life assessment testing revealed that the laser glazed OPC surfaces effected an increase in actual wear life of 1.3–17.7 times over the untreated OPC surface of concrete, depending upon the corrosive environment. The reasons for these marked improvements in the wear resistance and wear life of the HPDL generated glaze over the untreated OPC surface of concrete can be attributed to firstly, the vitrification of the OPC surface after HPDL treatment which subsequently created a much more dense and consolidated surface, and secondly, the generation of a surface with improved microstructure and phase which is more resistant in corrosive environments.

Investigations by Glass Sensors on the Corrosive Environmental Conditions at Stained Glass Windows with Protective Glazings in Europe

At 15 prominent churches and cathedrals in 7 European countries the environmental corrosive stresses at the stained glass windows were assessed by glass sensors. Special emphasis was given to the protective properties of different types of protective glazings. The obtained total stress level data, based on MI-glass sensor measurements, help to conclude on the appropriate choice of the ventilation systems and give information about specific environmental impacts. The results indicate that internally ventilated protective glazings have a higher protective effect than externally ventilated systems. The nonventilated type of protective glazing even raised the corrosive stresses for the stained glass windows.

高濃度カセイソーダ溶液中でのインコネル６００合金の腐食

Corrosion of Inconel 600 (I-600) in concentrated NaOH (1-20M) solutions was studied under various temperatures (50-140°C) and potentials. The solution treated (1050°C, 15min) and sensitized (650°C 10hrs) specimens were used. The results are as follows:(1) The polarization curves for the both specimens showed no change in electrochemical behavior in various corrosive environmental conditions at 50°C. However, the both specimens showed three peaks at higher temperatures than 50°C. The solution treated specimen showed a slightly low current density in the primary passive region and a slightly high current density in the secondary anodic peak, compared with those of the sensitized specimen.(2) The films formed on the specimen surface during corrosion tests in 20M NaOH solution at 140°C were made of NiO, Cr2O3 and Fe3O4.(3) The tests of crevice corrosion of I-600 and carbon steel (S15C) showed that general corrosion took place on the solution treated specimen, but the intergranular corrosion under the oxide films took place and it propagated to the crevice in the sensitized specimen.