Mass Loss Tests Research Articles

A sustainable bioplastic obtained from rice straw

A new bioplastic was produced from rice straw, an agricultural waste that generally is not recovered. For the synthesis the sample was treated by using the Naviglio extractor, then it was dissolved by trifluoroacetic acid. The material exhibits good mechanical properties, with tensile strength and elongation at break equal to 45 MPa and 6.1% and 10 MPa and 63% for dried and wet dumbbells, respectively. It results that the mechanical properties of the produced bioplastic, in its dry state, are comparable to those of polystyrene, while cast bioplastic in wet state is similar to plasticized poly(vinyl chloride). This demonstrates the high mechanical performance of the newly obtained bioplastic both in dry and wet status. The morphology of bio-based material, investigated by scanning electron microscopy, showed a uniform and compact surface structure. 2D X-ray Diffraction analysis reveals that bioplastic is essentially amorphous. Mass loss test noted that it is completely decomposed after being embedded in soil for 105 days. Industrial and environmental advantages of the newly obtained biomaterial are evaluated in terms of embodied energy and CO2 footprint production and in comparison with thermoplastic starch and other plastics. Finally, shape memory test revealed promising dual shape effects of the biomaterial, with a partial but significant shape recovery. In summary, depending on the environmental humidity, the material shows a dual mechanical behaviour that can be exploited to obtain shrink films and sheet or to drive shape memory effect. Therefore, we suggest rice straw bioplastic as a new potential eco-material for different application fields.

Soft computing model for analysing the effect of friction stir processing parameters on the intergranular corrosion susceptibility of aluminium alloy AA5083

Abstract Aluminium alloy AA5083 is prone to intergranular corrosion in marine environments. In an attempt to reduce the intergranular corrosion, AA5083 was subjected to friction stir processing (FSP). The FSP experimental trials were conducted as per face-centered central composite design with three levels of variation in FSP process parameters viz. tool rotation speed (TRS), tool traverse speed (TTS) and tool shoulder diameter (SD). Intergranular corrosion susceptibility of the processed specimens was assessed by performing nitric acid mass loss test. The mass loss of the specimens was correlated with the intergranular corrosion susceptibility as per the standard ASTM G67-13. The experimental results indicate that FSP had significantly reduced the intergranular corrosion susceptibility of the AA5083 alloy. Soft computing techniques namely Artificial Neural Network, Mamdani Fuzzy system, and Sugeno Fuzzy system were used to predict the intergranular corrosion (IGC) susceptibility (mass loss) of the friction stir processed specimens. Among the developed models, Sugeno fuzzy system displayed minimum percentage error in prediction. So Sugeno fuzzy system was used to analyze the effect of friction stir processing process parameters on the IGC of the processed specimens. The results suggest that stir processing of AA5083 at a TRS of 1300 rpm, TTS of 60 mm/min and SD of 21 mm would make the alloy least susceptible to intergranular corrosion.

Corrosion behaviors and mechanism of electroless Ni-Cu-P/n-TiN composite coating

In the present investigation, electroless Ni-Cu-P/n-TiN composite coating was prepared using alkaline citrate-based bath. X-ray diffraction (XRD), scanning electron microscopy(SEM), energy-dispersive spectroscopy(EDS), electrochemical measurements, weight loss tests and Raman spectrometer were used to character the properties of the coating. As the Cu content increased from 7.3 wt% to 24.8 wt%, the corrosion current density of the Ni-Cu-P/n-TiN coating decreased from 10.80 to 4.34 μA. And the inclusion of Cu in Ni-P alloy resulted in refinement and less porosity in microstructure. The addition of TiN resulted in a slight decline in anti-corrosion property of the coating. As the mass loss test showed, Ni-24.8%Cu-P exhibited perfect corrosion resistance. Studies by Raman spectroscopy on coatings proved that Cu(II)3(PO4)(OH)3, Cu(OH)2 and CuO were examined while no compound of nickel was found, and Cu exhibited preferred corrosion in saline solution, providing cathodic protection to Ni alloy.

Influence of aging treatment on corrosion behavior and mechanism of Mg–Y alloys

This paper studied the influence of aging treatment on the corrosion behavior and mechanism of Mg—Y alloys with different Y content through corrosion mass loss test, electrochemical test and corrosion morphologies observation. Results show that the peak-aging times of Mg–(0.25, 2.5, 5, 8 and 15) Y alloys at 250 °C were 4, 6, 10, 12 and 16 h. The aging treatment reduced the corrosion resistance of Mg–Y alloys, and the corrosion resistance of Mg–Y alloys became worse with increasing of the aging time. The change magnitude of the open circuit potentials for Mg–(0.25, 2.5)Y alloys was greater than that of Mg–(5, 8 and 15)–Y alloys. The polarization curves of Mg (0.25, 2.5, 5, 8 and 15) Y alloys had the similar shape after aging treatment, and the slopes of the anodic branch were greater than those of the cathodic branches. After aging treatment, the corrosion modes of Mg–0.25Y and Mg–(2.5, 5, 8 and 15) Y alloys were uniform corrosion and pitting corrosion with small local deep corrosion.

An experimental study of electrochemical incompatibility between repaired patch concrete and existing old concrete

This research program examines the performance of different patch repair strategies for repairing concrete bridge deck slabs, damaged due to premature corrosion of embedded reinforcing steel bars (rebars). The electrochemical compatibility between the repaired patch concrete and the existing old concrete in fifteen (1000 mm × 1000 mm × 200 mm) specimens was examined using half-cell potential, chloride content, rebar mass loss and corrosion penetration rate tests. The experimental results showed that the potential difference between the repaired patch concrete and the existing old concrete local corrosion increased significantly at the periphery of the patch, and gradually progressed into the repaired zone. This effect varied from one repair technique to another. Different measures to increase the service life of the repair system are also proposed, such as incorporating a sacrificial embedded anode, an impressed current cathodic protection system, along with the use of surface coating or membrane as an additional line of defence.

Influence of ignition of waste fishbone on enhancing heavy metal stabilization in municipal solid waste incineration (MSWI) fly ash

Abstract Natural fishbone was found effective for heavy metal stabilization (particularly Pb) in municipal solid waste incineration (MSWI) fly ash in a previous study presented by the authors. Natural fishbone containing hydroxyapatite (HAP) could stabilize Pb and Zn under appropriate conditions; however, undesirable release of Cu and P occurred in the presence of non-HAP fraction. Therefore, ignition of fishbone for optimizing this technique was investigated. Based on thermogravimetry and differential thermal analysis, mass loss test, and X-ray diffractometry, it was found that ignition not only removed the non-HAP fraction, but also increased the crystallinity of HAP in fishbone as a function of temperature. Various ignition temperatures were carefully evaluated based on the performance of candidate fishbones in metal stabilization under designated conditions. Accordingly, fishbone ignited at 430 °C (IGN-430) was selected. Both natural and IGN-430 fishbones were involved in the stabilization of heavy metals in fly ash under various scenarios. IGN-430 provided more efficient metal stabilization than natural fishbone under the same conditions, because it supplied more fishbone HAP at the same dose. The non-HAP fraction in fishbone was the main source of released P in the leachate and presumably facilitated Cu and Zn release from fly ash. This facilitation hindered metal stabilization, the influence of which was greater at higher liquid condition. Consequently, IGN-430 fishbone is preferred to natural fishbone used for metal stabilization in fly ash, as it provided a more efficient metal stabilization without undesirable release of the other elements. A solid-like condition was even more beneficial for heavy metal stabilization in fly ash by fishbone HAP.

A XANES Study of Sulfur Speciation and Reactivity in Cokes for Anodes Used in Aluminum Production

Availability of anode raw materials in the growing aluminum industry results in a wider range of petroleum cokes being used to produce carbon anodes. The boundary between anode grade cokes and what previously was considered non-anode grades are no longer as distinct as before, leading to introduction of cokes with higher sulfur and higher trace metal impurity content in anode manufacturing. In this work, the chemical nature of sulfur in five industrial cokes, ranging from 1.42 to 5.54 wt pct S, was investigated with K-edge XANES, while the reactivity of the cokes towards CO2 was measured by a standard mass loss test. XANES identified most of the sulfur as organic sulfur compounds. In addition, a significant amount is identified (16 to 53 pct) as S-S bound sulfur. A strong inverse correlation is observed between CO2-reactivity and S-S bound sulfur in the cokes, indicating that the reduction in reactivity is more dependent on the amount of this type of sulfur compound rather than the total amount of sulfur or the amount of organic sulfur.

Conditioning and Testing Protocol Combinations to Detect Asphalt Mixture Damage

Asphalt mixes often have many ingredients that can interact with each other. When put into service, where there are multiple environmental effects, there are many interactions that need mixture testing. This paper’s objective was to evaluate laboratory conditioning protocols coupled with subsequent property measurements for their ability to detect damage of asphalt mixtures in the southeastern U.S. climate (or similar climates). The investigation’s focus is the property measurements themselves, and in particular how a given test can simultaneously assess multiple types of damage (i.e. oxidation, moisture damage, and freeze-thaw damage). While in service, mixtures can be damaged in multiple manners so laboratory conditioning protocols that expose specimens to multiple types of damage are needed as are test(s) that can detect these damages in a manner that can help assess performance during service. Four plant produced mixtures with all virgin ingredients were evaluated at intermediate temperatures with mixture and binder tests. The mixtures were well suited for such a comparison because they consisted of all virgin binder. Indirect tensile (IDT) strength did not relate to Cantabro Mass Loss (CML) or binder test results, which was concerning. Even more concerning was IDT’s inability to respond to laboratory conditioning protocols that considered multiple environmental effects (i.e., oxidation, moisture, and freeze-thaw). CML results related to binder properties and were able to reasonably detect multiple types of environmental effects. As such, Cantabro testing is recommended over tensile strength for intermediate temperature mixture property assessments related to non-load associated environmental effects.

Durability properties of ternary blended geopolymer concrete under ambient curing

The present paper is an attempt to explore the durability properties of ternary blended geopolymer concrete incorporating fly ash, GGBS, wollastonite as appendage of strength parameters. The Large scale production of cement is triggering environmental problems. This has made the researchers to prefer supplementary cementatious material in fabricating concrete. Fly ash [1], GGBS is a waste material produced by industries used as binder material to way towards the waste utilization. Wollastonite, a naturally occurring mineral can be exploited in geopolymer concrete as a partial replacement of fly ash. G40 grade of geopolymer concrete is used in this study and mix design was built accordingly by replacing fly ash by the combinations of wollastonite and GGBS with suitable alkaline solution and Superplasticizer. A constant 50% of fly ash was used for all the mixes and rest 50% with the combinations of 15%,35%; 25%, 25%; 35%,15% of wollastonite and GGBS respectively .In this present experimental work durability tests (mass loss tests) like resistance to sulphateattack, chloride attack; sorptivity, abrasion resistance were explored for plain mix and optimal mix, which was extracted from previous experimental work of compressive strength properties of ternary blended geopolymer concrete.

Effect of high temperature on strength and mass loss of admixtured concretes

Chemical admixtures are used in concretes to prove some properties at ambient temperature. The admixtured concretes may present different behaviour at high temperature than at normal conditions. In this study, five different types of chemical admixtures – Superplasticizers (SP), hardening accelerators (HA), setting retarders (SR), air entrainers (AE) and water repellents (WR) – Were incorporated with different fraction of cement mass (0.5, 1.0, 1.5 and 2.0%), to investigate their influences on the strength and mass losses of concretes under high temperature. This study concerns the behaviour of admixtured concretes at ambient temperature 20 °C (normal conditions) and those subjected to temperatures 105 °C (oven dry) and 300 °C with a rate of 2 °C/min. Compressive-strength and mass loss tests were performed on the samples 10 × 10 × 10 cm3which were cooled up slowly to ambient temperature. It was concluded that among the chemical admixtures used, the superplasticizer (SP) significantly increased the workability of SPC. The tests results indicated that at a temperature of 300° C, the concrete with an air entrainer admixture caused the greatest loss of strength and mass when compared with others admixtured concretes. The lowest losses are those obtained for concretes with superplasticizers at this temperature.

Effects and mechanism on Kapton film under ozone exposure in a ground near space simulator

The effect on aircraft materials in the near space environment is a key part of air-and-space integration research. Ozone and aerodynamic fluids are important organizational factors in the near space environment and both have significant influences on the performance of aircraft materials. In the present paper a simulated ozone environment was used to test polyimide material that was rotated at the approximate velocity of 150–250 m/s to form an aerodynamic fluid field. The goal was to evaluate the performance evolution of materials under a comprehensive environment of ozone molecular corrosion and aerodynamic fluids. The research results show that corrosion and sputtering by ozone molecules results in Kapton films exhibiting a rugged “carpet-like” morphology exhibits an increase in surface roughness. The morphology after ozone exposure led to higher surface roughness and an increase in surface optical diffuse reflection, which is expressed by the lower optical transmittance and the gradual transition from light orange to brown. The mass loss test, XPS, and FTIR analysis show that the molecular chains on the surface of the Kapton film are destroyed resulting in CC bond breaking to form small volatile molecules such as CO2 or CO, which are responsible for a linear increase in mass loss per unit area. The CN and CO structures exhibit weakening tendency under ozone exposure. The present paper explores the evaluation method for Kapton’s adaptability under the ozone exposure test in the near space environment, and elucidates the corrosion mechanism and damage mode of the polyimide material under the combined action of ozone corrosion and the aerodynamic fluid. This work provides a methodology for studying materials in the near-space environment.

Electrochemical noise analysis on the pit corrosion susceptibility of biodegradable AZ31 magnesium alloy in four types of simulated body solutions

Magnesium alloys have been investigated as biodegradable implant materials since the last century. Non-uniform degradation caused by local corrosion limits their application, and no appropriate technology has been used in the research. In this study, electrochemical noise has been used to study the pit corrosion on magnesium alloy AZ31 in four types of simulated body solutions, and the data have been analyzed using wavelet analysis and stochastic theory. Combining these with the conventional polarization curves, mass loss tests and scanning electron microscopy, the electrochemical noise results implied that AZ31 alloy in normal saline has the fastest corrosion rate, a high pit initiation rate, and maximum pit growth probability. In Hanks’ balanced salt solution and phosphate-buffered saline, AZ31 alloy has a high pit initiation rate and larger pit growth probability, while in simulated body fluid, AZ31 alloy has the slowest corrosion rate, lowest pit initiation rate and smallest pit growth probability.

On the Interaction Between Erosion and Corrosion in Chromium Carbide Coating

In this paper, the effects of slurry flow velocity and impact angle on erosion–corrosion (E–C) behavior of the chromium carbide coating in NaCl solution containing SiO2 particle were investigated. A jet impingement system was used. The mass loss test, polarization curve and surface characterization were employed to examine the coating performance. The erosion–corrosion regime of the Cr7C3-coated and uncoated specimens was determined. Results showed that pure erosion and corrosion-enhanced erosion were the dominant regime for the uncoated samples. However, both the erosion and corrosion contributed to the coating damage. Mass loss values of the coated and uncoated samples increase with flow velocity. In addition, coated and uncoated samples experience maximum mass loss at 45° and 90°, respectively. Finally, E–C degradation mechanisms were evaluated using scanning electron microscopy. The images indicate the abrasive wear mechanism and lips removal as well as plastic deformation for the uncoated sample. Also, brittle fracture, cracking and flake fragmentation were recommended as the main fracture mechanism for the chromium carbide coating.

Corrosion Mechanisms in Dissimilar AZ31/AZ80 Friction Stir Welds

Corrosion of dissimilar friction stir welds (FSW) made in AZ31/AZ80 magnesium alloys was investigated using the scanning reference electrode technique (SRET), and microcapillary polarization technique, complemented by optical and SEM/EDX microscopy. The corrosion rate of the base metals along with the welded specimen was estimated by mass loss testing. The stir zone material in both alloys showed a higher corrosion potential than the base metal due to the partial dissolution of β-Mg17Al12 and Al-Mn particles. The basic corrosion mechanism in dissimilar welds was determined to be different from that of a similar joint. The corrosion behavior of the dissimilar FSW joint was governed by the galvanic coupling of the two alloys, and not by the microstructural evolution occurring during the welding process. The corrosion behavior of the joint was governed by the galvanic coupling between the α-Mg matrix in AZ31 and the Al-rich intermetallics in AZ80. The welded specimens exhibited the highest corrosion rate, while AZ80 was the most corrosion resistant material.

Enhancing Corrosion Resistance of Type 310S Stainless Steel in Carbonate Melt by Hot-Dip Aluminizing

Corrosion behavior of hot-dip aluminized coating formed on type 310S stainless steel was studied for the first time in carbonate melt at 650°C for solar-thermal applications. The heat pre-treatment at 800°C for 24 h endowed the coating with a high interdiffusion resistance at 650°C. Polishing out the rough outer surface of the coating enabled better estimation of the corrosion resistance. The aluminized coating having dense layers quickly and sufficiently alloyed with Cr by the high temperature heat pretreatment showed enhanced corrosion resistance in carbonate melt. Mass loss and electrochemical tests confirmed that the heat pre-treated aluminized coating decreased the corrosion rate of 310S stainless steel at least by two orders of magnitude. The formation of a ∼50 nm thick passive film of lithiated-alumina on the coating is responsible for the high corrosion resistance.

Intergranular corrosion susceptibility of friction stir processed aluminium alloy 5083

The amalgamation of high strength and low density of aluminium alloys makes it suitable for light weight structural applications. Aluminium alloy AA5083 is prone to intergranular corrosion, when exposed to aggressive chloride containing marine environments. When aluminium alloy 5083 is exposed to marine environments, the continuous network of secondary phase particles present in the matrix reacts with the chloride ions and dissolves into the solution, creating new cites for corrosion. In addition to this phenomenon, secondary phase particles form galvanic couple with primary phase of the matrix, accelerating the corrosion. With an objective to improve the intergranular corrosion resistance, AA5083 was subjected to friction stir processing (FSP). FSP trials were conducted by varying the tool rotation speed, tool traverse speed and tool shoulder diameter, as per face centered central composite design. The intergranular corrosion susceptibility of friction stir processed AA5083 was studied by nitric acid mass loss test according to the ASTM G67-04 standard. Mathematical model was generated using linear – radial basis function and the model was used to study the effect of process parameters on the intergranular corrosion susceptibility of friction stir processed AA5083. The results indicate that FSP results in refinement of grain structure, dispersion and partial dissolution of secondary phase particles in the matrix, thereby reducing the intergranular corrosion susceptibility of AA5083.

Mechanical and corrosion properties of AA5083 alloy sheets produced by accumulative roll bonding (ARB) and conventional cold rolling (CR)

Influence of accumulative roll bonding (ARB) and conventional cold rolling (CR) on the mechanical and corrosion properties of AA5083 alloy sheets has been studied. Tensile tests showed significant increase in strength and a decrease in elongation after each ARB deformation and cold rolling reductions. Results of nitric acid mass loss test (NAMLT) revealed that cold rolled and ARB processed specimens were resistant toward intergranular corrosion (IGC) in as‐deformed state. However, after 7 days of sensitization at 100 and 150 °C, cold rolled material became IGC sensitive, while ARB specimens stayed IGC resistant. IGC susceptibility can be correlated with different morphology and distribution of β‐phase (Mg2Al3) precipitated during sensitization. It was found that extensive shear banding contributed a favorable distribution of β‐phase precipitates in the structure of IGC resistant ARB processed specimens. In case of IGC susceptible conventionally cold rolled specimens, large amount of β‐phase precipitated preferentially along the elongated grain boundaries. Electrochemical parameters were in a good correlation with the results of NAML tests, which in turn, confirmed the superiority of ARB multilayered structure over conventional cold rolled structure in terms of IGC susceptibility and corrosion stability.

Formation mechanism and mechanical properties of surface nanocrystallized Ti–6Al–4V alloy processed by surface mechanical attrition treatment

In the present work, surface mechanical attrition treatment (SMAT) was proposed to achieve surface nanocrystallization on Ti–6Al–4V surface via high-energy planetary ball milling method using a planetary ball mill. The characteristics of microstructure were studied using different methods. Surface nanocrystallization is achieved on Ti–6Al–4V substrate. The process of refinement could be summarized into four steps. During the refinement process, the reticular continuous beta phase performs a significant role, it cracked, broke up and moved to each side along the grain boundaries. The movement of beta grains has the capabilities of effectively optimizing the grain orientation and accelerating the further refinement of alpha grains. Twinning also plays an important role during the refinement. The grain orientation between different types of grains seems to be larger than that of same type grains. The interface will be divided into smaller nanocrystalline grains once the dislocation density breaks the threshold. Then, the balance will be achieved again and owns a higher critical value which cannot be broken, then a stable grain size can be achieved ultimately. The results of microhardness, friction coefficient and wear mass loss tests of SMAT samples indicate that the mechanical behaviors of substrate are greatly enhanced after this novel SMAT treatment.

Reducing the corrosion rate of magnesium via microalloying additions of group 14 and 15 elements

A characteristic of magnesium (Mg) dissolution is that dissolution is accompanied by a concomitant increase in the hydrogen evolution reaction (HER), a phenomenon known as cathodic activation. When magnesium undergoes free corrosion or forced dissolution in response to anodic polarisation, cathodic activation is manifest, which allows magnesium dissolution to readily proceed. However, recent work revealed that alloying magnesium with micro additions of arsenic, As (a group 15 element) was capable of retarding cathodic activation, resulting in a significant reduction in the corrosion rate of Mg-As alloys. As such, in the pursuit of elements with similar chemical and electrochemical properties to arsenic, but with less toxicity, a number of group 14 and 15 elements were alloyed with magnesium and reported herein. Based on the binary alloying additions studied herein, it was revealed that Bi, Ge, Pb, Sb and Sn, demonstrated suppression of cathodic activation of Mg following anodic polarisation (about one order of magnitude lower based on the cyclic galvanostatic-potentiostatic testing), in addition to lower free corrosion rates (about one order of magnitude based on the mass loss and hydrogen evolution testing). Employing a number of corrosion rate assessments, including online atomic emission spectroelectrochemistry, it was shown that reduction in Mg corrosion rates – historically considered difficult to achieve – can be robustly demonstrated. The present work has implications for the development of more corrosion resistant Mg alloys, Mg anodes for cathodic protection, or for the use of Mg as a primary battery electrode.

The repassivation response from single cycle anodic polarization: The case study of a sensitized Al-Mg alloy

The repassivation behaviour of artificially aged 5083-H111 Al-Mg alloy in near neutral NaCl solutions was investigated by means of single cycle anodic polarization. Artificial aging was carried out at 150 °C during different times up to 360 h. The characterization of the microstructure and composition by XRD, SEM/EDS and metallographic analyses pointed out most favoured grain-boundary β(Al3Mg2) phase precipitation for 168 h of isothermal treatment time. Nitric acid mass loss test (NAMLT) and microhardness measurements indicated the highest degree of sensitization (DoS) and developed strength for 168 h as well. For all the aging conditions, the potential drop at high currents during the reverse scan of the cyclic polarization was detected at the pit transition potential Eptp with similar but higher values than the corrosion potential of β phase (Ecorr ≈ −900 mV vs SCE). The associated current density iptp and the steepness of the potential drop increase as the amount and contiguity of β phase precipitates along grain boundaries. The onset and sustenance of metastable conditions that limit the simultaneous repassivation of all the corroded surfaces are driven by the anodic dissolution of β(Al3Mg2). Metastable processes that limit the hydration of metal ions while producing high local hydrogen concentration are more likely to involve the formation/decomposition of reactive hydride intermediates. Eptp corresponds to the mixed electrode potential at which both metal dissolution and hydrogen evolution occur beyond some distance into the cavity, while iptp evaluates the catalytic activity of the corroding surfaces. The effective anodic charge transfer coefficient αeff determined from the steepness of the potential drop estimates the contribution of Cl− electromigration in response to local electrodissolution processes.