Higher Corrosion Rate Research Articles

The differences in the corrosion product compositions of Methanogen-induced microbiologically influenced corrosion (Mi-MIC) between static and dynamic growth conditions

Currently, corrosion rates (CR) and/or corrosion products (CP) obtained for methanogen-induced microbiologically influenced corrosion (Mi-MIC) on carbon steel are mainly analyzed from static-incubations. By using a multiport-flow-column, much higher CRs (0.72 mm/yr) were observed, indicating static-incubations are not suitable for determining the corrosive potential of Mi-MIC. With the combination of various analytical methods (ToF-SIMS/SEM-EDS/SEM-FIB) and contrary to previously published data, we observed that CPs contained phosphorus, oxygen, magnesium, calcium and iron but lacked carbon-related species (e.g. siderite). Overall, siderite nucleation is disrupted by methanogens, as they convert aqueous bicarbonate into carbon dioxide for methanogenesis resulting in increased localized corrosion.

Brass dezincification with a bipolar electrochemistry technique

A bipolar electrochemistry approach was applied to characterise the dezincification of brass. The dissolution of both Cu and Zn resulted in the formation of Cu2O, CuO, ZnO and CuClx, with corrosion product formation characterised as a function of the potential gradient. At low potentials, protective corrosion products formed, with compositional changes observed via dezincification up to a critical applied potential threshold. Above the critical potential, no corrosion products could form, resulting in higher corrosion rates. The influence of corrosion product formation after bipolar electrochemistry assessment is compared to results from standard three-electrode potentiodynamic polarisation tests.

Post Forming Analysis and In Vitro Biological Characterization of AZ31B Processed by Incremental Forming and Coated With Electrospun Polycaprolactone

Abstract Main problems related to the adoption of magnesium alloys for temporary orthopedic prostheses manufacturing are (i) the need of an efficient production process and (ii) the high corrosion rate compared with the bone healing time. In this work, the single-point incremental forming (SPIF) process, an effective and flexible solution for manufacturing very small batches even composed by one piece, was investigated. Tests were conducted on AZ31B-H24 sheets and were aimed at understanding the effect of temperature on the mechanical characteristics (microstructure, hardness, and roughness) of the sheet after the above-mentioned forming process and their correlation with both the corrosion rate and the cytocompatibility. In addition, after the forming process, samples processed by SPIF were coated by electrospun polycaprolactone (PCL) to reduce the corrosion rate and to further improve the cytocompatibility. Grain refinement was achieved thanks to the combined effect of temperature and strain rate during forming and finer grain size resulted to improve the magnesium corrosion resistance. In simulated body fluids, the electrospun PCL-coated samples exhibited a slower pH increase compared with uncoated samples. No indirect cytotoxic effects were detected in vitro for MC3T3-E1 cells for both coated and uncoated samples. However, cells colonization was observed only on electrospun PCL-coated samples, suggesting the importance of the polymeric coating in promoting the adhesion and survival of seeded MC3T3-E1 cells on the implant surface.

The study of corrosion behaviour api 5l steel in sea water using immersion test method

API 5L steel, a low carbon steel with a high alloy content, is often used as an underwater construction material or oil and gas pipeline. Banten has a wide sea area and has a long coastline where part of the coastline is used for petrochemical industries. There are three coast areas of Banten, namely Bayah Rangkasbitung, Anyer and Merak, that are used for petrochemical industries. Most of those industries use API 5L steel for underwater construction materials and pipes to channel seawater, chemical compounds, gas and oil. Whereas, seawater will greatly affect the lifetime of API 5L construction steel because it can cause corrosion. The purpose of this study is to analyze the corrosion characteristics of API 5L steel affected by the environment of seawater media and the temperature of seawater in accordance with its natural conditions. The samples of API 5L steel were immersed in seawater media with variation of immersion time of 5, 10, 15 Days and variation of immersion temperature of 20°C, 40°C, and 60°C. In this study, a series of tests were carried out, namely immersion test, weight loss test, and SEM test (Scanning Electron Microscopy). The highest corrosion rate on API 5L steel is 0.39 mmpy which belongs to Merak’s seawater media in the immersion time of 15 Days and the temperature of 60°C, while the lowest corrosion rate on the API 5L steel is 0.013 mmpy which belongs to Bayah’s seawater media with a time of immersion of 10 Days and a temperature of 20°C.

Microstructure and corrosion resistance of TiN/TiO2 nano-composite film on AZ31 magnesium alloy

The high corrosion rate of Mg alloy restricts its application. In this paper, a nano-composite film as TiN/TiO2 was introduced to Mg alloy to improve the corrosion resistance. The nano-composited film was fabricated by atomic layer deposition (ALD) and in-situ oxidation (20 SCCM oxygen flow, at 250 °C, duration ≥ 20 min). When oxygen is introduced, the initial ALD-ed crystalline TiN layer is rapidly oxidized till the amorphous TiO2 layer is saturated. A stable TiN/TiO2 nano-composited film would be obtained then. X-ray photoelectron spectroscopy depth (XPS-depth) and transmission electron microscopy image (TEM) show that the nano-composite film has an interlayer structure. The nano-composite film shows good adhesion to the Mg alloy substrate in the nano-indentation analysis. Moreover, the nano-indentation scratches heal to a certain degree after 48 h, which means the film could self-heal. With the film, the surface potential mapping is not only overall higher but also less fluctuating by scanning Kelvin probe (SKP) analysis. There is a higher Ecorr (increasing ~0.42 V) and a much lower icorr (decreasing ~1/200) for potentiodynamic polarization (PDP) measurement. Equivalent circuit fitting for electrochemical impedance spectroscopy (EIS) profile changes from Rs(CPE1Rct) to Rs(CPE2(Rf(CPE1Rct))). The film makes less corroded withing a more uniformed corroded mode during neutral salt spray test (NSS). All these indicate that Mg alloy corrosion resistance is greatly improved. The work not only provides a flexible method for the interlayer composite film fabrication but also make an effective surface modification for Mg alloy corrosion resistance.

Noninvasive In Situ NMR Study of "Dead Lithium" Formation and Lithium Corrosion in Full-Cell Lithium Metal Batteries.

Capacity retention in lithium metal batteries needs to be improved if they are to be commercially viable, the low cycling stability and Li corrosion during storage of lithium metal batteries being even more problematic when there is no excess lithium in the cell. Herein, we develop in situ NMR metrology to study “anode-free” lithium metal batteries where lithium is plated directly onto a bare copper current collector from a LiFePO4 cathode. The methodology allows inactive or “dead lithium” formation during plating and stripping of lithium in a full-cell lithium metal battery to be tracked: dead lithium and SEI formation can be quantified by NMR and their relative rates of formation are here compared in carbonate and ether-electrolytes. Little-to-no dead Li was observed when FEC is used as an additive. The bulk magnetic susceptibility effects arising from the paramagnetic lithium metal were used to distinguish between different surface coverages of lithium deposits. The amount of lithium metal was monitored during rest periods, and lithium metal dissolution (corrosion) was observed in all electrolytes, even during the periods when the battery is not in use, i.e., when no current is flowing, demonstrating that dissolution of lithium remains a critical issue for lithium metal batteries. The high rate of corrosion is attributed to SEI formation on both lithium metal and copper (and Cu+, Cu2+ reduction). Strategies to mitigate the corrosion are explored, the work demonstrating that both polymer coatings and the modification of the copper surface chemistry help to stabilize the lithium metal surface.

(Invited) Effect of Bentonite Dry Density on Corrosion of Embedded Copper

As per international consensus on the best practice for managing used nuclear fuel (UNF), the NWMO, plan to isolate and contain UNF within a multiple-barrier system, underground in a deep geological repository (DGR) [1]. In the proposed design, used fuel bundles will be sealed in copper-coated carbon steel used fuel containers (UFC), encased in blocks of highly compacted bentonite clay, and emplaced ~500 m below ground in the DGR. Any gaps between the rock walls and the bentonite blocks will then be filled with a bentonite gapfill material (GFM).Due to its small pore size, high swelling pressures, and cation exchange properties [2], the bentonite will significantly limit the transport of active species to and from (in the case of a UFC failure) the UFCs. The high swelling pressure can suppress a potential UFC corrosion induced by sulphate reducing bacteria (SRB) by decreasing the clay pore space and lowering water activity [3]. Those properties of the bentonite clay are a function of several physical and chemical parameters. The goal of this work is to investigate the effect of bentontie dry density, presence of oxygen, and evolution of conditions on corrosion of copper in contact with bentonite, and on SRB viability, by varying water composition and GFM dry density.In this work we are conducting a series of experiments in bentonite-filled modules exposed to ocean conditions (ocean modules, OM) and more controlled laboratory-based conditions (pressure vessels, PC). The OM are porous vessels containing copper coupons embedded in GFM that has been compacted to various dry densities. The modules are then placed in the Pacific Ocean at up to 2.6 km depth for months-to-years at a time where they are exposed to seawater with hydrostatic pressures representative of potential DGR pressures. PC experiments contain copper coupons embedded in GFM are pressurized to 100 bar with Type-1 water for varying durations up to 1 year. After exposure, copper coupons are analyzed by SEM, XPS, FIB, and AES. The change in topography is evaluated using CLSM, the water activity of the bentonite assessed, and 16s RNA analysis used to determine the presence of SRB.Two OMs, both with cold-spray (Cucs) and wrought (Cuw) copper coupons, with GFM (dry density of 1.25 or 1.45 g/cm3) were exposed to seawater at 90 meters deep for 6 months. Analysis found the copper surface, post-experiment, to be non-uniformly corroded, possibly due to non-uniform wetting, and subsequently swelling, of the clay. The surface corrosion products consisted of Cu2O (~85 %at), Cu2S (~ 5 %at), CuCl (~3 %at), and CuO (~ 3 %at). Cuw had higher amounts of Cu2O and lower amounts of Cu2S at both GFM dry densities. Both the Cuw and Cucs exposed to the higher density GFM had lower amounts of Cu2S and higher amounts of Cu2O on the surface. This may be the result of non-uniform swelling, decresed mobility of the sulphide or a decrease in the number of metabolically active SRBs, or a combination of those factors [3]. Mass loss measurements, determined that Cucs had a higher corrosion rate than Cuw; however, Cuw corrosion rates were less affected by the GFM dry density variation. Overall, the increase in bentonite dry density resulted in a decrease in copper corrosion rates, with the Cucs corrosion rate being decreased more significantly than that of Cuw. Profilometry measurements of the surface, performed after removal of the corrosion products, showed a decrease in surface roughness on Cucs as the GFM dry density was increased, but the surface roughness of Cuw was not significantly affected.The experiments performed in PCs for 1 month duration, found similar results. Cross-sections of the film formed at the copper surface revealed the presence of copper, oxygen, and sulphur, unevenly distributed across the copper surface, accounting for the non-uniform corrosion observed. The corrosion rates were significantly higher than those in the OM experiments, due to higher oxygen concentration. Profilometry measurements concluded the Cucs and Cuw surfaces had lower roughness than those in the OM experiments. Noronha. Deep Geological Repository Conceptual Design Report Crystalline/Sedimentary Rock Environment, NWMO., Toronto, ON, Canada, Report# APM-REP-00440-0015 R001, 2014.Muurinen. Measurements on Cation Exchange Capacity of Bentonite in the Long- Term Test of Buffer Material (LOT). Report# 2011-10; POSIVA: 2011.Stroes-Gascoyne, C.J. Hamon, D. Priyanto, D. Jalique, C. Kohle, W. Evergen, A. Grigoryan, D. K. Kober, Microbial Analysis of a Highly Compacted Wyoming MX-80 Bentonite Plug Infused Under Pressure with Distilled Deionised Water over a Period of Almost Eight Years, NWMO, Toronto, ON, Canada, TR-2014-20, 2014.

(Invited) Atmospheric Corrosion Monitoring in Cold Arctic Climate Using Modular Corrosion Test Racks

Atmospheric corrosion is a complex process, which involves chemical, electrochemical, and physical changes to the metal exposed. Atmospheric corrosion occurs when a metal surface is under a thin layer of moisture, but not completely immersed, and the metal surface corrodes while exposed to environmental factors. The arctic and sub-arctic region identified by the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) has an average temperature of -18oC or less during winter. It is commonly assumed that there is very little to no corrosion in cold environments. However, previous studies in the Antarctic and Arctic regions have shown significant corrosion damage when exposed to cold conditions. Studies in the sub-arctic region of Canada, Norway, and Russia show extensive atmospheric corrosion rates (when compared to Antarctica) due to human developments and the resulting increase in mining and metallurgical industries. Experimental and theoretical work has shown that the electrochemical process proceeds at temperatures as low as -25oC to -20oC . Moreover, very little corrosion data are available for metal alloys exposed to cold arctic and sub-arctic conditions. The two important factors that affect atmospheric corrosion rates are aerosol chlorides (or salt-laden snow from the marine environment or deicing salts on roads) and time of wetness (TOW) along with other climatic parameters such as rainfall, temperature, humidity. Factors that drive the atmospheric corrosion in cold climates are winds that can bring in salt-laden snow from the marine environment and the use of de-icing salts can also contribute to high levels of chlorides. The eutectic point or the freezing point of de-icing salts can be lowered to -50oC, melting the ice/snow layer on top of metal samples. This phenomenon keeps metal samples moist for much longer periods, thus increasing the TOW. In the presence of chlorides and moisture, extensive atmospheric corrosion damages can be observed on metal samples. Another contributing factor to high corrosion rates is low rainfall, which in turn cannot periodically wash off the deposited chlorides and SO2 on top of the samples. In addition, ever-increasing ambient temperatures due to climate change in recent years affect the snow presence on top of the metal samples. The temperature of the samples is not too high to evaporate the snow/ice deposited, but high enough to cause melt and sustain moisture for longer periods of time. This leads to the formation of varying thickness of wet ice/snow layers on the metal surface. Long hours of sunlight in the summer also increase the surface temperature of metal samples beyond the ambient temperatures, causing dew formation and condensation, which in turn results in higher TOW. The atmospheric corrosion damage in cold environments is close to the main human activity, which is concentrated near the coastal areas. The substantial human growth and climate change in the arctic and sub-arctic region pushes for a renewed better understanding of the atmospheric corrosion mechanisms that can lead to good choice of materials selection and better design practices for infrastructure and other applications. The combination of urbanization and proximity to marine environments make arctic and sub-arctic regions in North America, particularly Alaska, an important natural laboratory to study atmospheric corrosion in cold regions. Design and establishment of modular corrosion test racks equipped with weather stations will be discussed. The angle of exposure can be changed to 0, 30 and 45-degrees to the horizontal (see the attached figure). This will allow us to test the metals alloys exposed to different angles for the same exposure period and study the effect of snow/ice retention on top of the metal surface. Figure 1

(Keynote) Corrosion of 1018 Plain Carbon Steel in Petroleum-Based and Renewable Diesel Fuel/Seawater Mixtures

The substitution of biofuels for conventional fuels can result in unexpected issues and forms of corrosion. A study was conducted on corrosion rates and the identification of corrosion products that formed on plain-carbon 1018 steel (UNS G10180) exposed in seawater/fuel mixtures of petroleum-based F-76; a 50%:50% by volume (50:50 v/v) blend of F-76 and hydro-treated renewable diesel derived from algae (HRD-76); or HRD-76 for various time durations (i.e., 3 days, 10 days, 1 month, 6 months, and 1 year). The 1018 coupons were immersed in bottles with the bottom half of the sample submerged in the seawater layer and the top half in the fuel layer. The 1018 steel has a composition which is within specifications for steels typically used for pipelines and storage vessels and tanks. Energy dispersive X-ray analyses (EDXA), X-ray diffraction (XRD), Raman spectroscopy, and FTIR spectroscopy were used to identify the corrosion products. To differentiate between abiotic electrochemical corrosion and microbiologically influenced corrosion (MIC), various permutations of filtered and unfiltered fuel and seawater combinations were used as the exposure media. A 0.22 micron filter was used to produce sterile seawater and fuel. Both aerobic and anaerobic conditions were examined. Natural, off-shore, surface seawater and synthetic seawater according to ASTM International specifications were used in the study. Hence, the test conditions were aerobic or anaerobic of the following seawater-fuel mixtures: 1) filtered seawater/filtered fuel, 2) filtered seawater/non-filtered fuel, 3) non-filtered seawater/filtered fuel, and 4) non-filtered seawater/non-filtered fuel.Corrosion rates of 1018 plain-carbon steel in the seawater-fuel mixtures were driven primarily by oxygen reduction and were highest in HRD-76, followed by the F-76/HRD-76 blend, and then F-76. This ordering corresponded to that of the dissolved-oxygen diffusion coefficients which were also ordered from highest to lowest as HRD-76, F-76/HRD-76 blend, and F-76.The region of steel in the seawater layer was most severely corroded due to the high corrosivity induced by chlorides. Corrosion was dominated by abiotic mechanisms and overshadowed any effects of MIC. At the fuel/water interface and zones submerged in the seawater layer, rust formation showed an inner black layer identified as magnetite and an outer red/yellow layer identified as lepidocrocite and goethite. The amount of magnetite in the inner layer increased with increasing content of HRD-76 in the fuels. Hence, the highest amount of magnetite was observed for the coupons exposed in HRD-76 followed by those in the HRD-76/F-76 50v:50v blend and least in the F-76. White precipitates identified as Mg(OH)2 (magnesium hydroxide), MgO (magnesium oxide), Na2CO3 (sodium carbonate), Na2CO3•H2O (thermonatrite), Na3H(CO3)2(H2O)2 (trona), CaCO3 (calcite and aragonite) formed in the fuel zone and was shown to be a consistent visual indicator for a high corrosion rate of steel. Precipitation was likely induced by a high amount of oxygen reduction (in the fuel layer) that generated OH-, which precipitated the carbonates and hydroxides. The presence of the white precipitates was most abundant on the coupons exposed to the HRD-76 and to a lesser degree on those exposed to the HRD-76/F-76 50v:50v blend, which is consistent with higher rates of oxygen diffusion and hence corrosion in the HRD-76 fuel. Acknowledgements: This work was supported under the Hawaii Natural Energy Institute’s Asia Pacific Research Initiative for Sustainable Energy Systems (APRISES) program, University of Hawaii at Manoa, Office of Naval Research (Grant Award Number N00014-13-1-0463).

The Effect Analysis of Coating Thickness Variation and Mixture Composition of Magnesium – Flake Glass on Epoxy Coating on Abrasive Resistance, Adhesion Strength, and Prediction of Corrosion Rate of ASTM A36 Steel Plate

Steel cannot be separated from the marine manufacturing industry. It is important to control the corrosion rate of steel used for offshore structures. The coating method can be used in mobilization areas and splash zones that have high corrosion rates due to sustained friction loads in the marine environment. The purpose of this study was to analyze the different in adhesion strength, abrasion resistance, and corrosion rate prediction of ASTM A36 low carbon steel plate with coating thickness variations of 300µm, 500µm, and 700µm and Magnesium Carbonate - Flake Glass mixture variations of 10%, 20%, and 30%. In the pull-off test, the highest value of adhesion strength was obtained from specimen with 300µm coating thickness and 10% Magnesium Carbonate - Flake Glass mixture with a value of 5.67 Mpa. The highest abrasion test value was obtained from specimen with 700µm coating thickness and 30% Magnesium Carbonate - Flake Glass mixture with a value of 0.91 Wear Cyces per Micrometer. Whereas in the three cells electrode test, the highest value was found at specimen with 700µm coating thickness and 30% Magnesium Carbonate - Flake Glass mixture with a value of 0,00010 mmpy.

Corrosion risk assessment of geothermal reinjection wellbore in Xining Basin, China

A potential corrosion risk exists during the re-injection of geothermal water in Xining Basin of China due to air entering the well caused by it being open. In this paper, a series of corrosion experiments using metal coupons and geothermal waters was conducted to evaluate the corrosion risk for steels in different typical geothermal waters by dissolved air. A novel and comprehensive prediction model for O2 corrosion rate in reinjection wellbores was established, and a sensitivity analysis of factors influencing air corrosion risk in reinjection wellbores was carried out. The results show that the main corrosive components in the geothermal water from the Xining Basin are Cl−, SO42−, H+ and the O2 added, which can cause a uniform corrosion and a small amount of local corrosion on the surface of carbon steel. The main corrosion products are FeO(OH) and Fe3O4. A high O2 partial pressure and flow velocity, a moderate temperature and salinity, and low pH promote a high corrosion rate for carbon steel. When the geothermal water is injected with a small amount of air, only the deeper part of the wellbore with a high temperature and pressure will suffer a serious corrosion risk, while when a large amount of air is mixed with geothermal water and injected, a huge corrosion risk will be imposed on the entire wellbore. Anti-corrosion measures should be taken if air is added to a wellbore. Removing the O2 from the geothermal water is the most effective solution for carbon steel. In addition, the established corrosion rate prediction model can consider more influencing factors and specializes in the situation of a low O2 partial pressure, which can be used as an effective tool to assess the corrosion risk in reinjection wells.

Effects of friction stir processing on the microstructure, mechanical and corrosion behaviors of an aluminum-magnesium alloy

This article deals with the corrosion behavior of friction stir processed aluminum-magnesium alloys undergoing electrochemical measurements, including potentiodynamic polarization and electrochemical impedance spectroscopy. The effects of friction stir processing (FSP) critical parameters such as the rotational tool speed (w in the range of 800–1400 rpm) and traverse velocity (v in the field of 50–200 mm/min) along with varying cooling rates imposed using submerged cooling medium (air, water/dry-ice mixture, and liquid nitrogen) on the microstructural features and mechanical properties of Al-Mg alloys in two tempering states of annealed and wrought were characterized. Then, by assessing the electrochemical behavior of the friction stir-modified stirred regions produced using varying cooling rate and initial temper, a correlation between the microstructural details with the mechanical and chemical properties was established. The experimental results revealed the significant grain refinement down to ~1 μm following FSP treatment by controlling the processing conditions, which had a detrimental impact on the electrochemical behavior due to the activation of grain boundary corrosion phenomenon. The primary tempering state of alloy in the form of stored strain energy played a critical role by controlling the fraction of sub-boundaries and recrystallized grains upon FSP modification. The inferior electrochemical property reported for the FSP treated annealed Al-Mg alloy under processing conditions of w = 800 rpm and v = 200 mm/min, as the less noble structure with the highest corrosion rate (CR) of 0.01814 mm/year.

Correlating the Five-Parameter Grain Boundary Character Distribution and Corrosion Behavior of Zinc-Carbon Nanotube Composite Coatings

Grain boundary engineering (GBE) of coatings using optimum weight fractions of foreign inclusions can improve corrosion resistance performance. This is illustrated here by correlating the corrosion behavior with the five-parameter grain boundary character distribution analysis of Zn-carbon nanotube (Zn-CNT) composite coatings. Zn-CNT composite coatings with different volume fractions of CNTs were electrodeposited on mild steel substrates by dispersing different amounts of CNTs (4, 6, 8, 10, 15, and 20 mg/L) in the Zn electrolyte bath. All the coatings exhibited compact and crack-free morphology. Electrochemical impedance spectroscopy (EIS) measurements were conducted in 3.5 wt pct NaCl solution. The Nyquist and Bode plots showed a decrease in the coating corrosion rate with initial CNT addition up to the Zn-CNT3 coating (produced from 8 mg/L of CNT in the electrolyte), after which the corrosion resistance decreased with continued addition of CNTs. This showed that an optimum exists for CNT in the Zn coating to achieve high corrosion resistance performance. Orientation distribution maps from the coating cross section were acquired using the electron backscatter diffraction (EBSD) technique for correlating the microstructure with the corrosion data. The lower corrosion rate in the Zn-CNT3 coating was attributed to the strong basal plane texture in grains along the growth direction. The angle/axis misorientation showed that most grain boundaries have [ $$ 2\overline{11} 0 $$ ] and [ $$ 10\bar{1}0 $$ ] axis misorientations signifying special grain boundaries. The five-parameter analysis showed that these grain boundaries are mostly symmetric and tilt boundaries, which are low-energy boundaries, whereas in Zn and Zn-CNT6 (produced from 20 mg/L of CNT in the electrolyte) coatings, the higher corrosion rates were due to the high fraction of high-angle grain boundaries (HAGBs), grain texture along the growth direction that corresponds to an orientation that is active in the corrosive environment, and the absence of special grain boundaries.

Effect of TiN, TiAlCN, AlCrN, and AlTiN ceramic coatings on corrosion behavior of tungsten carbide tool

Hard ceramic coatings are widely used for cutting and forming applications because these coatings on the surface of the tools considerably improve the oxidation, wear, and corrosion resistance of the materials. The aim of this study is to investigate the electrochemical corrosion behavior of TiN, TiAlCN, AlCrN, AlTiN, and multi-layered coat of AlTiN on tungsten carbide (WC) at different mediums. Coatings were performed using the cathodic arc evaporation-physical vapor deposition (CAE-PVD) method. The corrosion behaviors of the coated and uncoated WC materials were carried out with potentiodynamic polarization curves which used to calculate the corrosion rate of the tested materials at the pH values of 2, 7, and 10 at the room temperature. The surface morphologies of the uncoated and coated samples were examined by a scanning electron microscopy (SEM) before and after the corrosion testing. The corrosion experiment results indicated that the corrosion rate (114.7 × 10–6 mpy) of TiAlCN coating was much lower than WC substrate material (38.83 mpy) in pH = 7. The highest corrosion rate (1.559 mpy) was obtained for TiN coating, although the corrosion rate (490.8 × 10–9 mpy) of AlCrN coating was lower in pH = 10. The corrosion resistance of AlCrN coating was also the highest, even if in acidic environment.

In Vivo Evaluation of Bioabsorbable Fe-35Mn-1Ag: First Reports on In Vivo Hydrogen Gas Evolution in Fe-Based Implants.

This work investigates the influence of Ag (1 wt%) on the mechanical properties, in vitro and in vivo corrosion, and biocompatibility of Fe-35Mn. The microstructure of Fe-35Mn-1Ag possesses a uniform dispersion of discrete silver particles. Slight improvements in compressive properties are attributed to enhanced density and low porosity volume. Fe-35Mn-1Ag exhibits good in vitro and in vivo corrosion rate of Fe-35Mn due to an increase in microgalvanic corrosion. Gas pockets, which originate from an inflammatory response to the implants, are observed in the rats after 4 weeks implantation but are undetectable after 12 weeks. No chronic toxicity is observed with the Fe-35Mn-1Ag, suggesting acceptable in vivo biocompatibility. The high corrosion rate of the alloy triggers an increased level of nonadverse tissue inflammatory responses 4 weeks after implantation, which subsequently subsides at 12 weeks. The Fe-35Mn-1Ag displays properties that are suitable for orthopedic applications.

The Effect of Circulation of 3% HCL Solution On the Corrosion Rate of Aluminum

Corrosion is usually called rusting. Corrosion to aluminum is carried out by circulating and non-circulating methods. The specimens were placed in 3% HCl solution, each with 3 specimens in one vessel. There are 9 specimens in 3 vessels. In this study, aluminum was immersed with a circulation of 385 L/hour and 432 L/hour and also without circulation with immersion time for 4 days. The highest corrosion rate was obtained in aluminum soaked in 3% HCl for 4 days with a circulation of 432 L / hour, 0.5215 Mpy. The lowest corrosion rate was obtained for aluminum immersed in 3% HCl for 4 days without circulation, 0.1830 Mpy.

SINTESIS GREEN INHIBITOR EKSTRAK DAUN TREMBESI (Samanea saman (Jacq.) Merr) SEBAGAI PEREDUKSI LAJU KOROSI LOGAM BAJA KARBON

Extract of trembesi leafs consist tannins compound that can reducing corrosion rate. This studey was to examine the efficiency of trembesi leaf extract as a inhibitors of corrosion rate. In this study, carbon steel metal was used as an immersion object in 10% HCl solution as a corrosion medium. Trembesi leaf extract were added in the corrosive medium with variations in volumes of 3, 6, 9, 12 mL with carbon steel immersion for 14 days. Corrosion rate was calculated using the weight loss method. The results shows, the lowest corrosion rate was obtained in the addition of 9 mL inhibitor concentration of 0.008989 cm/year and the highest corrosion rate was without the addition of an inhibitor of 0.011669 cm/year. The highest inhibitor efficiency value was 22.97% with the addition of 9 mL.

Surface Characterization and Corrosion Resistance of Biomedical AZ31 Mg Alloy Treated by Microarc Fluorination.

The application prospect of biodegradable materials is being studied extensively. However, the high corrosion rate and its alloys in body fluids have been major limitations of the application of pure Mg (magnesium). To improve corrosion resistance of biodegradable AZ31 Mg alloy, we adopted microarc fluorination within a voltage range of 100-300 V in 46% hydrofluoric acid. To obtain morphologies, chemical compositions, and structural characteristics, field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were performed, respectively. Results showed that the coating was mainly composed of MgF2. Electrochemical corrosion and immersion tests proved that the corrosion resistance of MAF-treated AZ31 Mg alloy was significantly improved compared with untreated AZ31 Mg alloy in HBSS (Hank's Balanced Salt Solution). Current densities of AZ31, MAF100, MAF150, MAF200, MAF250, and MAF300 were 342.4, 0.295, 0.228, 0.177, 0.199, and 0.212 μA/cm2, respectively. The roughness test indicated that samples under MAF treatment of 200 V, 250 V, and 300 V had large surface roughness. Meanwhile, the contact angle measurement and surface free energy test suggested that those samples had smaller contact angle and higher SFE than Ti. Thus, MAF-treated AZ31 Mg alloy might have promising application in various fields.

Corrosion Behavior of Al in Ethanol–Gasoline Blends

The corrosion behavior of pure aluminum (Al) in 20 v/v% ethanol–gasoline blends has been studied using electrochemical techniques. Ethanol was obtained from different fruits including sugar cane, oranges, apples, or mangos, whereas other techniques included lineal polarization resistance, electrochemical noise, and electrochemical impedance spectroscopy for 90 days. Results have shown that corrosion rates for Al in all the blends were higher than that obtained in gasoline. In addition, the highest corrosion rate was obtained in the blend containing ethanol obtained from sugar cane. The corrosion process was under charge transfer control in all blends; however, for some exposure times, it was under the adsorption/desorption control of an intermediate compound. Al was susceptible to a localized, plotting type of corrosion in all blends, but they were bigger in size and in number in the blend containing ethanol obtained from sugar cane.

Investigation on corrosion behaviour of aluminium 6061-T6 alloy in acidic, alkaline and salt medium

Aluminium 6061 is a precipitation-hardened aluminium alloy, containing magnesium and silicon as its major alloying elements. T6 temper 6061 has an ultimate tensile strength of at least 290 MPa (42,000 psi) and yield strength of at least 240 MPa (35,000 psi). More typical values are 310 MPa (45 ksi) and 270 MPa (39 ksi), respectively. Corrosion acts on a continuous basis and it is a tedious issue to normalize it or to eradicate it. Hardened aluminium alloy containing Magnesium and Silicon as its major alloying elements. This research work deals with investigating the corrosion behaviour of this Aluminium 6061-T6 reaction in the acidic alkaline and in the salt medium. By analyzing the comparative results it will clarify that the Aluminium 6061 T6 alloy has higher corrosion rate in alkaline solution than in the acidic solution. The corrosion resistance of aluminium alloy is higher in solutions of acids and salts containing sulfate and nitrate ions than in chloride ions.