Corrosion Weight Loss Research Articles

Corrosion resistance of Mg–8·8Li alloy compared with AZ91

The superlight Mg–Li alloys exhibit good formability but poor corrosion resistance due to the alloying of lithium. In this paper, the corrosion behaviour of Mg–8·8Li alloy was investigated by electrochemical measurements, corrosion morphology observations and weight loss determination. The results indicate that Mg–8·8Li alloy displays worse corrosion resistance than AZ91D alloy in the early stages of corrosion. However, the corrosion resistance of AZ91D alloy declines and becomes worse than Mg–8·8Li alloy with increasing exposure time. In addition, it is found that a 250°C annealing treatment has a detrimental effect on the corrosion resistance of Mg–8·8Li alloy.

Effect of pre-corrosion on fatigue life of high strength steel 38CrMoAl

The effect of pre-corrosion on fatigue behavior of high strength steel 38CrMoAl was investigated with a fatigue test method using the accelerated pre-corrosion specimen in the neutral salt spray environment. The methods of weight-loss and energy dispersive spectrum (EDS) were adopted. The corrosion weight-loss rate was fitted with the test time using power law, and the relationship between the corrosion weightloss rate and the time was formulated. Moreover, the fatigue behaviors of the steel for different pre-corrosion time were investigated by the axis-direction tensile fatigue test. The fatigue life distribution characteristics of the pre-corrosion specimens were studied using the statistical probability methods, and the mathematical expectations and the standard tolerances of the material fatigue lives after different pre-corrosion time were obtained. It was found that the crack initiation of the high strength steel was accelerated by the preferential corrosion at the local plastic deform areas. The fatigue life obeys the lognormal distribution perfectly. Furthermore, within the common time range of the engineering, the standard tolerances of the logarithm of the fatigue life were independent of the pre-corrosion time.

Effect of Y on Microstructure and Corrosion Resistance of AZ61 Magnesium Alloy

The effect of Y addition on the microstructure of AZ61 alloy was investigated by optical microscopy (OM), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The corrosion behavior of AZ61 alloy with Y addition in 3.5 % NaCl solution was studied by static weight loss and polarization curves corrosion tests. The results show that AZ61 alloy with Y addition can refine grain size of the matrix and alter the distribution of the phase β-Mg17Al12 from continuous network morphology transition to small and dispersive distribution along the grain boundary by forming the second phase Al2Y which has a high melting point. In addition, the addition of Y can decrease the corrosion current density of AZ61 magnesium alloy in 3.5% NaCl solution, thereby improving the corrosion resistance of AZ61 magnesium alloy. Results show that AZ61 magnesium alloy with 1.0% Y has the most refined microstructure and the best corrosion resistance.

Effect of Temperature on the Corrosion Resistance of QPQ Treated Specimens in CO2 Environment

When the pressure of CO2 is 2 MPa, through the autoclave corrosion tests of annealed N80 steel specimens in simulated oil field water solution at different temperature, the mechanism of corrosion and the change rule of corrosion resistance with the change of temperature were discussed. In the autoclave tests, some iron elements of the specimens become Fe2+ions and the Fe2+ ions go into the solution, which results in the corrosion weight loss. Scaling develops because the CO32- ions in the simulated oil field water solution react with iron elements of the specimen. To QPQ treated specimens, with the increase of temperature, the compactness of the scaling increase, the corrosion weight loss and the weight of scaling decrease. In the same temperature, the corrosion weight loss and the weight of scaling of QPQ treated specimens are both lower than that of untreated specimens.

Anticorrosion and cytocompatibility behavior of MAO/PLLA modified magnesium alloy WE42

Recently, biodegradable magnesium alloys have been introduced in the field of cardiovascular stents to avoid the specific drawbacks of permanent metallic implants. However, the major obstacle of the clinical use of magnesium-based materials is their rapid corrosion rate. In this paper, a composite micro-arc oxidation/poly-L: -lactic acid (MAO/PLLA) coating was fabricated on the surface of the magnesium alloy WE42 to improve its corrosion resistance and the cytocompatibility of the modified materials was also investigated for safety aim. In our study, the morphology of materials was analyzed by Scanning electron microscopy. Potentiodynamic polarization was used to evaluate the corrosion behavior of the samples and corrosion weight loss was used to demonstrate their degradation rate. Furthermore, we applied cytotoxicity test in testing the cytocompatibility of the modified samples. The results showed that the PLLA coating effectively sealed the microcracks and micropores on the surface of the MAO coating by physical interlocking to interfere the corrosion ions. The corrosion rate was decreased and the cyototoxicity test showed that the MAO/PLLA composite coating WE42 had good cytocompatibility.

Influences of cube texture on etched foil capacitance

The influences of aluminum cube texture on etched foil qualities and current efficiency were studied in this paper. The present results indicated that the decrease of cube texture (volume fraction) would lead to the decrease of tunnel densities on etched foils. Current efficiency changed little with cube texture and could reach up to 98%. The same current efficiency led to the same electrochemical corrosion weight loss, which caused the etched foils with a smaller tunnel density had a larger tunnel size. The same electrochemical corrosion weight loss would also lead to the etched foils produced by different cube texture foil have the same folding endurance. The etched foil produced by the foil with a better cube texture would have a larger tunnel density, which caused the capacitance of it was larger.

Study on the Complex of Sodium Tungstate and Urotropine as Inhibitors against Stainless Steel Corrosion in the NaCl Solution

The corrosion weight loss method and polarization curve measurement were conducted to study the effects of the complex inhibitor of sodium tungstate and urotropine on the corrosion of 304 stainless steel in the 3.5% NaCl solution. The results indicated that the complex inhibitor has good synergistic inhibitory effect for stainless steel in the NaCl solution. Combining sodium tungstate and urotrpine at a total concentration of 500 mg/L, when the mass ratio of sodium tungstate to urotrpine was 7:3, the inhibitory effect was optimum. In addition, the probable inhibitory mechanism was analyzed.

Study on Carbonation and Corrosion Resistance of Reinforced Recycled Concrete

By processing waste into recycled aggregate concrete, and producing recycled concrete aggregate with 50 percent of it replacing natural gravel, we make a study of different curing conditions on the carbonation of recycled concrete as well as the resistance capacity of steel corrosion. The experiment results indicate that the depth of carbonation of recycled concrete increases sharply with the standard curing period lowering. The recycled concrete steel corrosion resistance rate decreases as standard maintenance ages. The recycled concrete steel corrosion rate is much lower than the general concrete steel. The steel corrosion weight loss rate of general concrete is less than 0.3%, with no rusting of the steel. The steel corrosion weight loss rate of recycled concrete is mostly more than 0.3%, with apparent rusting.

Modeling Corrosion Property of High Vanadium High Speed Steel (HVHSS) under H<sub>3</sub>PO<sub>4</sub> Medium Condition Using Artificial Neural Network

The components in slurry pump suffer serious corrosion abrasion under H3PO4 medium. Presently, High chromium cast irons are often used to produce the components in slurry pump. New high vanadium high speed steel(HVHSS) has been proved to be a more excellent wear resistance material than high chromium cast irons under abrasive wear and rolling wear. In order to apply HVHSS in slurry pump to replace high chromium cast irons, the corrosion properties of HVHSS were tested under different H3PO4 medium concentration conditions. Using back-propagation (BP) neural network, the non-linear relationship between the corrosion weight losses (W) and H3PO4 concentration, corrosion time (C, t) is established on the base of the dealing with experimental data. The results show that the well-trained BP neural network can predict the wear weight loss precisely according to H3PO4 concentration and corrosion time. The prediction results reveal that the corrosion time and H3PO4 concentration have obvious effect on corrosion weight loss of HVHSS. And corrosion weight loss takes on linear relationship with corrosion time and H3PO4 concentration, respectively.

Modeling Corrosion Property of High Chromium Cast Iron under H<sub>3</sub>PO<sub>4</sub> Medium Condition Using Artificial Intelligence

The components in slurry pump suffer serious corrosion and abrasion in the phosphorus fertilizer manufacturing process because they undergo corrosion of H3PO4 medium and impact of particles at the same time. Presently, High chromium cast irons are often used to produce the components in slurry pump. In order to reveal the corrosive law, the corrosion properties of high chromium cast iron with 26wt.%Cr content (Cr26) were tested under different H3PO4 medium concentration conditions. Using back-propagation (BP) neural network, the non-linear relationship between the corrosion weight losses (W) and H3PO4 concentration, corrosion time (C, t) is established on the base of the dealing with experimental data. The results show that the well-trained BP neural network can predict the wear weight loss precisely according to H3PO4 concentration and corrosion time. The prediction results reveal that corrosion weight loss rises linearly with increasing corrosion time. The H3PO4 concentration has obvious effect on corrosion property. When H3PO4 concentration is lower than about 0.5mol/L, high chromium cast iron has well resistance to H3PO4 corrosion. However, the corrosion resistance of high chromium cast iron rapidly decreases when the H3PO4 concentration exceed about 0.8 mol/L. It is suggest the high chromium cast iron be used under the condition of H3PO4 concentration of lower 0.8 mol/L.

Accelerating Corrosion Test Study on Galvanized Q345 Steel

Galvanized Q345 steel specimens were accelerating corroded with accelerating environment spectrum for equivalent 1, 3, 4 and 5 years, and then its corrosion behavior was studied based on macro corrosion appearances, micro corrosion appearances, weight loss, pits depth and fatigue strength. The results show that, i because the zinc coating can protect the matrix metal from corroding, the corrosion resistance of galvanized Q345 is much better than Q345; ii between the 1st year and the 4th year, pitting corrosion is dominative, and after the 4th year, the corrosion form transforms from pitting corrosion to uniform corrosion; iii after corrosion for 5 years, the zinc coating was not destroyed completely, and with the turning point of the 4th year, the corrosion rate of the zinc coating becomes higher firstly and then gets lower, which agrees with previous study.

Study on the Combined Anticorrosion Method of Thermal Spraying and Coating of Carbon Steel in Deposit Water of Storage Tank

Storage tank was protected from corrosion with the combined method of thermal spraying and coating, and corrosion resistance of the coating was studied through on-the-spot static weight loss method, potentiodynamic polarization curve and electrochemical AC impedance test. The result showed that the hanging slices with thermal sprayed aluminum powder, glass flake and epoxy resin coating had least weight loss and best corrosion resistance after 10 months of corrosion with on-the-spot weight loss experiment. In the polarization curve experiment, the anodic polarization curve of the hanging slices with thermal sprayed aluminum powder and glass flake had passivation characteristics, strong polarization area shifted left, weak corrosion current and greater polarization resistance. In the AC impedance spectra, hanging slices with thermal sprayed aluminum powder and glass flake had greater capacitive reactance arc and better corrosion resistance.

Performance of phosphate–alumina pigments in waterborne paints for protection of cold-rolled steel

Core–shell theory presents a new easy method to obtain high performance, economic, and eco-friendly anticorrosive mixed pigments. The core–shell pigments in this work are prepared by depositing a surface layer of an expensive efficient anticorrosive pigment (phosphates) on a bulk of less expensive extender pigment (alumina). The combination of these two compounds led to the production of new pigments with improved properties different from each of its individual components; and consequently these improved properties led to changing the efficiency of protection properties of paint films containing these new pigments. The new pigments were characterized using XRD, SEM, TEM, and EDAX analysis to elucidate their structure and prove the presence of phosphate ions on the surface of alumina. These pigments were also evaluated according to ASTM measurements. Then they were incorporated in three groups of emulsion paint formulations based on styrene acrylic emulsion copolymer, and comprising different concentrations of Zn, Mg, and 1Zn·1Mg phosphates/alumina core–shell pigments; in addition to a control formulation free of these pigments, to evaluate their efficiencies in anticorrosive paints for protection of cold-rolled steel. Chemical, physical, and mechanical measurements were carried out, besides corrosion resistance tests and weight loss of steel panels under paint films which were determined in 5% NaCl solution for 28 days. The results proved that the prepared formulations containing the prepared pigments could protect steel efficiently from corrosion compared to the control specimen. Groups II and III containing higher weight percentages of prepared pigments showed the best performance in corrosion protection, and the best performance among these two groups was paint films containing magnesium phosphate/alumina pigments.

1119 MG合金メッキ材の静的腐食抵抗と腐食疲労特性に関する研究(OS11-5 材料の疲労挙動と損傷評価-環境-)

Corrosion fatigue tests and corrosion weight-loss tests in 3% NaCl solution were conducted using the anodized Mg alloy to study a correlation between corrosion fatigue strength and corrosion resistance of the material.

Bearing capacity and corrosion weight losses of the bonded metal joints in the conditions of Indonesia, North Sumatra province

: The article is focused on the analysis of the bonded metal joints capacity and corrosion weight losses in the conditions of equatorial Indonesia – North Sumatra province. For the purpose of the given article, the province was divided into three main climatic zones: Medan, Balige, Pagarbatu, where the dependence was observed of the bonded joints capacity on the duration of the weather exposure. The joints life and their further usability were predicted based on the analyses of the measured values.

The influence of tin and silver as microstructure modifiers on the corrosion rate of Pb-Ca alloys in sulfuric acid solutions

The effect of microstructure modifiers, Sn and Ag, on the corrosion rate of commercial Pb–Ca alloy in H2SO4 electrolyte was investigated by the potentiodynamic polarization and by the weight loss corrosion rate measurement at the open circuit potential. The effect of microstructure modification of the Pb–Ca alloy, provoked by the alloying with tin and silver as well as by the proper thermo-mechanical treatment, is recorded by optical microscopy. The weight loss experiments have shown three- to five-fold decreases in the corrosion rate of ternary Pb–Ca–Sn and quaternary Pb–Ca–Sn–Ag alloys, compared to the results for primary Pb–Ca alloy. It is largely in accordance with the results of potentiodynamic polarization measurements that showed comparable decrease in the passive current density of the modified alloys. The obtained results are discussed in terms of the synergetic effect of the addition of modifiers and the thermo-mechanical treatment on to the Pb–Ca alloy microstructure refinement, and accordingly the increase in their corrosion resistance.

Effect of pretreatment on anticorrosive phosphating conversion coating of sintered NdFeB magnets

Different pretreatment procedures were investigated, and alkaline cleaning and acid picking pretreatment techniques were developed, for the first time, to achieve a phosphating conversion coating on a sintered NdFeB magnet. The effects of different additives on the pretreatment procedures are illustrated by several visual schematics. Corrosion immersion tests showed that NdFeB substrates with optimum pretreatment and phosphating conversion coating procedures can endure at least 17 h before pitting occurs in 5 wt-% neutral NaCl solution. Potentiodynamic polarisation tests in 3·5 wt-% NaCl solution show that corrosion potential Ecorr increases nearly 60 mV by combination of pretreatment and phosphating conversion coating, and the corresponding polarisation impedance value R is increased by 50%. The corrosion weight loss tests also confirm that compact and anticorrosive phosphating conversion coating could be formed on the NdFeB substrate with the optimum pretreatment.

Effects of Electric Field Treatment on Corrosion Behavior of a Ni-Cr-W-Mo Superalloy

Electric field treatment was performed on a Ni-Cr-W-Mo superalloy to investigate the effects of electric field treatment on its corrosion behavior. The microstructure evolution and the elements distribution at grain boundaries of both annealing twins and high angle grains were examined. The results show that the corrosion resistance can be improved by the electric field treatment and both of the corrosion weight loss and corrosion rate are decreased with the increasing treating time. When the alloy is electric field treated at 1093 K for 600 min with 4 kVcm � 1 , the intergranular corrosion rate is 65.3 mmy � 1 with the decreasing ratio of 25.1% compared with the untreated one, and the immersion corrosion rate is 3.9 mmy � 1 with the decreasing ratio of 57.9% compared with the untreated one. The redistribution of elements between the original high angle grain boundaries and the annealing twins occurred by the formation and growth of the annealing twins during the electric field treatment, as well as the improvement of exhaustion of Cr and Mo elements at the grain boundaries. With the increasing treating time, a large amount of original high angle grain boundaries are replaced and the continuously distributed original grain boundaries are separated, which leads to the retardation the growth rate of the corrosion ditches. The corrosion resistance of the alloy is improved due to the changes of corrosion behavior of the grain boundary. Moreover, the promotion effect of electric field treatment on the atom diffusion rate decrease the exhaustion tendency of Cr and Mo elements on both sides of normal high angle grain boundary. Those can be considered as the reasons of improving the corrosion resistance after electric field treatment. (doi:10.2320/matertrans.MF200905) With the rapid development of the aerospace engineering, the alloying elements ratio of superalloy is increased to meet the demands for long-term service at elevated temperatures. Besides the excellent properties including the high-temper- ature strength and plasticity, the oxidation existence, high- temperature corrosion resistance and irradiation resistance of the alloy are also required. 1-3) The distribution and size of carbides at grain boundaries increase especially when the alloy was experienced long-term services. It is easy for the intergranular rupture to occur at the grain boundary under corrosive environment. Researches on nickel-base Ni-Cr- W-Mo and GH4586A superalloys after electric field treat- ment reveal that annealing twins occurred in alloys and the number of annealing twins increase with the increasing treated time. During the deformation, the crack propagation direction changes with the annealing twins, and this leads the increase of both the uniformity and work of plastic deformation. The plasticity can be improved greatly without strength changing. 4-7) The coherent twin boundary with low energy can be caused with electric field treatment on nickel-base super- alloys and the fraction of low energy boundary can be increased. This agrees with the Grain Boundary Design and Control-Grain Boundary Engineering (GBE). 8-12) It aims at preventing the intergranular rupture and intergranular corro- sion by obtaining low energy and coherent boundary with high fraction in polycrystalline. As conventional GBE techniques, such as deformation heat treatments including strain recrystallization and strain heat treatment can be used to increase the fraction of coherent grain boundary in austenite steel, nickel-base alloy, copper and aluminum alloys. In other words, it can be considered that the electric field treatment will become one of the GBE techniques for obtaining high fraction of coherent grain boundary with low energy. In the present study, the electric field was employed on a nickel-based Ni-Cr-W-Mo superalloy to investigate the effects of electric field on its corrosion resistance. The mechanisms were also discussed. The present work aims to study potential application for electric field treatment on the progress of research on superalloys. 2. Material and Experimental Procedures

Corrosion Characteristics and Mechanical Properties of Inconel 622 Weld Overlay of Waterwall Tubes in Coal Fired Boilers

Recently in Japan, boiler waterwall tube damage such as fireside corrosion and circumferential cracking in a low NOx environment has become a serious issue, despite the fact that relatively lower sulfur content coal is typically being used than in the US. Thermal spray coating is the most popular method for tube protection in Japan, and thermal spray coating tubes are used for this purpose.However, extensive damage to thermal spray coating tubes from cracking and exfoliation has recently been experienced. It is reported that the thermal fluctuations that occur as a result of operating changes create alternating stress, leading to cracking and exfoliation of the thermal sprayed thin coating. Corrosion-resistant weld overlays, such as stainless steel type 309, alloy 625 and alloy 622, are now commonly used to protect corrosion of boiler tubes in low NOx coal fired boilers in the US. In order to develop a fundamental understanding of the high temperature corrosive behavior of alloy 622 weld overlay, gaseous corrosion testing and certain mechanical tests for consideration of long-term aging were undertaken. After one year of service in the low NOx combustion environment of a coal fired supercritical boiler, field tests on alloy 622 weld overlay panels are continuing.This report describes the behavior of alloy 622 overlay panels in a field test installed in a Japanese supercritical boiler, the laboratory results of weight loss corrosion testing, and mechanical tests related to aging.

Hydrogen permeation and corrosion behaviour of high strength steel 35CrMo under cyclic wet–dry conditions

Hydrogen permeation behaviours of high strength steel 35CrMo under different cyclic wet–dry conditions have been investigated by using Devanathan–Stachurski's technique. Four electrolytes were used: distilled water, seawater, seawater containing 1500 ppm H2 S and seawater containing 0 · 03 mol L2 1 SO2. The corrosion weight loss of 35CrMo in the wet–dry cycles was measured simultaneously. The experimental results show that hydrogen can be detected at the surface opposite to the corroding side of the specimen during wet–dry cycles and the permeation current density during a wet–dry cycle showed a maximum during the drying process. The hydrogen permeation was obviously promoted by Cl2 ions, H2 S and SO2. The hydrogen permeation in the real marine atmosphere has also been investigated. There is a clear correlation between the amount of hydrogen permeated and the corrosion weight losses. Results show the importance of hydrogen permeation that merits further investigation.