Metal Loss Research Articles

Investigation of the Hydrogen Ingress and Embrittlement Induced By Corrosion of API 5L Natural Gas Pipeline Steels

Internal corrosion of natural gas pipelines is a major cause of many related accidents. In addition to the metal loss due to corrosion, hydrogen ions produced during corrosion can lead to the degradation of ductility of metals used in these pipelines. The effect of hydrogen generated through internal corrosion on current pipeline steels was studied. Three grades of API 5L steels commonly used in natural gas infrastructure were investigated: X56, X65, and X100. The rates of hydrogen diffusion were determined electrolytically via a Devanathan-Stachurski cell. The steels were subjected to hydrogen embrittlement tests using electrolytic hydrogen charging and constant strain rate tensile tests. The microstructure analysis of the investigated materials and the fracture surfaces was performed via scanning electron microscopy (SEM). This presentation reports on work to extend the life of the natural gas pipeline network via understanding the mechanisms of hydrogen ingress and subsequent embrittlement induced by corrosion processes.

Durability Assessment of Transition Metal Oxygen Electroreduction Catalysts with on-Line Flow Cell Trace Elemental Analysis

Proton exchange membrane hydrogen fuel cell (PEMFC) cathodes for commercial applications are typically based on platinum group materials that exhibit remarkable oxygen reduction reaction (ORR) activity and stability. Despite this performance, the high cost of such platinum electrodes prevents a more rapid transition to a more sustainable hydrogen economy involving PEMFCs. Platinum-free transition metal ORR catalysts have been identified and tested as high activity, low-cost alternatives with well-established protocols, though understanding the durability of these materials would require more experimental efforts. Techniques for measuring catalyst degradation typically involve activity loss measurements, surface-sensitive microscopy and spectroscopy, and liquid aliquot collection for metal loss quantification that are all performed post-catalysis for extended periods of time. Experiments using this approach provide valuable information about overall catalyst material degradation but usually cannot elucidate mechanistic or potential-dependent phenomena that may occur on shorter time scales. More rigorous experiments with synchrotron radiation have been utilized to investigate the degradation mechanisms of platinum-based fuel cell catalysts but studies on other transition metal materials are less widespread due to the high time requirements and limited accessibility of synchrotron beamlines for such experiments. In our work, we utilize an on-line electrochemical flow cell coupled with an in-house inductively coupled plasma-mass spectrometer (ICP-MS) for evaluation of fuel cell catalyst degradation in acidic electrolyte environments. Oxygen and nitrogen gas saturated electrolytes with a constant pH of 1 but differing chemical identity are flowed through the cell and across a working electrode composed of non-platinum transition metals. Dissolved metal ions are convectively transported to the ICP-MS where they are measured with up to part per trillion resolution with a time delay of ~4 seconds, enabling millisecond resolution of transient catalyst surface degradation. We evaluate the oxygen mass transport capabilities of our custom-machined flow cell against a commercial flow cell and compare to the much more established rotating disk electrode (RDE) technique for distinguishing ORR activity. Cyclic voltammetry measurements in oxygen-saturated electrolyte on various metal foils indicate potential dependent corrosion in agreement with what is expected from a Pourbaix (potential-pH) diagram of stability. In contrast, potential cycling these materials in the ORR-relevant range reveals degradation during ORR electrocatalysis that increases with ORR current to differing amounts as a function of the metal in a way that has not been previously characterized. Notably, degradation appears to be suppressed in the ORR potential range when saturating the electrolyte with nitrogen compared to oxygen, suggesting that surface-bound oxygen and ORR intermediates have a potential-dependent role in enabling degradation. Probing degradation during ORR conditions further with varied cyclic voltammetry scan rates and directions reveals more fundamental information about the timescales of catalytic corrosion processes and may inform the development of activation protocols that enhance the lifetime of ORR catalyst materials during operation. Through electrochemical flow cell testing in various pH 1 electrolytes, we make suggestions for electrolyte compositions and catalyst operation potential ranges that maintain activity and stability to advise fuel cell catalyst researchers in developing platinum-free PEMFC cathode materials. We are also developing additional flow cell configurations to allow testing of other non-precious ORR catalyst morphologies such as nanoparticle catalysts on carbon supports. The on-line ICP-MS flow cell architecture accelerates materials stability and degradation experiments for rapid assessment of platinum-free ORR electrocatalysts through in-house experiments and direct comparability to established electrochemical techniques.

Evaluation of Commercial Corrosion Sensors for Real-Time Monitoring of Pipe Wall Thickness under Various Operational Conditions.

In this study, we investigated the performance and reliability of commercial corrosion sensors for monitoring the integrity of piping systems in various fluid environments as an alternative to ultrasonic transducers. To this end, we investigated pipes’ wall-thinning using commercial electrical resistance (ER), linear polarization resistance (LPR), and ultrasonic transducer (UT) sensors under various operating environments. A pilot-scale closed-loop test bed was built to simulate a real pipeline flow situation, from which the sensor data were collected and analyzed. Experimental results indicate that, in the case of the LPR sensor, it is challenging to accurately measure the corrosion rate when a specific measure exceeds the threshold in a severe corrosion environment. In contrast, the ER sensor could measure metal loss under all conditions and reflect the corresponding characteristics. The metal loss (about 0.25 mm) of the real pipe after the experiment was confirmed to be equal to the metal loss (0.254 mm) measured by the sensor. Furthermore, the regression analysis revealed a high correlation between the results obtained from the ER and UT sensors. Thus, evaluating the remaining thickness of the piping system using the commercial ER sensor is deemed to be effective and reliable.

HYDROCARBON PROFILE AND HEAVY METAL LEVELS OF EDE-ONYIMA LAKE IN OKARKI-ENGENNI, RIVERS STATE, NIGERIA

Freshwater quality is deteriorating as a result of ongoing threats from both anthropogenic and natural sources, resulting in an overall loss of ecological integrity petroleum hydrocarbon profiles and heavy metals (Mg, Fe, Ni, Mn, Pb, Cd, Cu, Cr, and Zn) were determined in water samples collected at six sampling sites in Ede Onyima lake, Okarki-Engenni, Rivers State, Nigeria using gas chromatography, flame ionization detector, and Atomic Absorption Spectroscopy. Results showed that total petroleum hydrocarbon (TPH) varied from (0.27 -252.20 mg/L) with mean : 77.30 mg/L; Total hydrocarbon content (0.43 - 347.70 mg/L) with mean : 97.97 mg/L; Benzene, Toluene, and Xylene (9.00E-04- 6.60 mg/L) with mean : 0.11mg/L; polycyclic aromatic hydrocarbons (0.16- 3.51mg/L) with mean : 1.93mg/L. The heavy metal results showed Mg (1.11- 8.67mg/L) with mean : 2.87 mg/L; Fe (0.13 - 20.73mg/L) with mean : 7.29mg/L; Mn (0.001- 5.92 mg/L) with mean : 1.69 mg/L; Pb (0.06 - 0.06 mg/L) with mean : 0.06 mg/kg; Cu (6.33E-04- 0.31 mg/L) with mean : 0.07mg/L; Zn (9.90E-04- 0.38 mg/L) with mean : 0.08 mg/L; Ni (0.04 - 0.04 mg/L) with mean : 0.04 mg/L; Cd and Cr were less than 0.01 mg/L. The CWQI was used to capture the overall spatial and temporal trends in water quality in the Ede Onyima lake. The results showed that while PAHs and Fe exceeded guideline values and failed 100% of the time. The large magnitude of F3 is as a result of varying degrees of failure of Mn, Fe, THC, TPH, and PAHs, all of which exceeded regulatory thresholds by several magnitudes. Furthermore, the flood event had a significant effect on the quality of the water, remobilizing pollutants' availability while washing away legacy contaminated streambed deposits during baseflow.

Gain-Assisted Giant Third-Order Nonlinearity of Epsilon-Near-Zero Multilayered Metamaterials.

We investigate the third-order nonlinear optical properties of epsilon-near-zero (ENZ) Au/dye-doped fused silica multilayered metamaterials in the visible spectral range for TM incident by using nonlocal effective medium theory at different incidence angles. The nonlocal response affects the permittivity of anisotropic metamaterials when the thickness of the layer cannot be much smaller than the incident wavelength. By doping pump dye gain material within the dielectric layer to compensate for the metal loss, the imaginary part of the effective permittivity is reduced to 10−4, and the optical nonlinear refractive index and nonlinear absorption coefficient are enhanced. The real and imaginary parts of the permittivity are simultaneously minimized when the central emission wavelength of the gain material is close to the ENZ wavelength, and the nonlinear refraction coefficient reaches the order of 10−5 cm2/W, which is five orders of magnitude larger than that of the nonlinear response of the metamaterial without the gain medium. Our results demonstrate that a smaller imaginary part of the permittivity can be obtained by doping gain materials within the dielectric layer; it offers the promise of designing metamaterials with large nonlinearity at arbitrary wavelengths.

Enhanced selectivity of platinum group metals concentrates at Kola MMC’s chemical and metallurgical shop

An upgrade of the nickel refining circuit realized in 2019 by Kola MMC when the plant adopted an electrowinning process for extracting nickel from sulphate-chloride solutions resulting from chlorine dissolution of tube furnace nickel powder, led to a considerable decrease in the amount of nickel sludge generated. The latter is treated at the Chemical and Metallurgical Shop by liquid phase sulphation in the presence of sulphuric acid. Other materials containing precious metals are now used in the sulphation process. For example, the concentrate obtained as a result of flotation of the tube furnace nickel powder chlorine dissolution residue. The main purpose of sulphation is to obtain selective concentrates of platinum group metals. The products include platinum-palladium concentrate and a concentrate of concomitant metals that contains at least 20 % of rhodium. The qualitative and quantitative characteristics of the concentrates define the process to be applied, as well as the recovery of base metals during further refining. A change in the feedstock supplied to the Chemical and Metallurgical Shop affected the distribution of rhodium between the target concentrates leading to a greater loss of concomitant metals in the refining process. The high demand for platinum group metals at the global market, the drawbacks of the current process, as well as the new type of feedstock supplied created a need for the process parameters to be studied and adjusted. The paper examines the process flowsheet and looks at ways to raise the selectivity of the final products by means of liquid phase sulphation in the presence of sulphuric acid.Contributors to this paper include M. A. Lastochkina, who oversees the precious metals section at the Hydrometallurgical Laboratory of Gipronikel Institute.

Experimental and numerical study of compressive sleeve type A repair of pipes with metal loss

Experimental and numerical study of compressive sleeve type A repair of pipes with metal loss

Wall thickness image construction in wellbore casings using data-driven inversion of magnetic flux leakage

We describe the response of magnetic flux leakage measurements obtained in wellbore casings and detail an analytical approach for inverting the data to construct a 3D image of metal loss for the general case in which the magnetic permeability of the casing is unknown. This approach contrasts with current practice which assumes a defect shape and attempts to deduce metal loss from one or more response metrics matched to a library of defects generated under laboratory conditions for that shape. The traditional approach breaks down where defects do not conform to the assumed shape and when the properties of the laboratory casing are not the same as the properties of the installed casing. Moreover, there is no direct way to know whether magnetic flux in the casing is at saturation level; thus, the measurement could be operating in a nonlinear part of the magnetization curve whose shape also is unknown. The new method makes no assumptions about defect shape and approximates the relevant part of the magnetization curve within an inversion process that transforms the flux scan into a metal loss scan showing the shape and depth of metal loss. The approach is validated using data from simulations, laboratory tests, and field operations. Unlike images of flux distribution, thickness profiles reconstructed from the results of the inversion reflect the actual distribution of metal loss to a useful level of accuracy and thereby enable the casing’s mechanical integrity to be assessed with greater confidence.

Sub-Surface Defect Depth Approximation in Cold Infrared Thermography.

Detection and characterisation of hidden corrosion are considered challenging yet crucial activities in many sensitive industrial plants where preventing the loss of containment or structural reliability are paramount. In the last two decades, infrared (IR) thermography has proved to be a reliable means for inspection of corrosion or other sub-surface anomalies in low to mid thickness metallic mediums. The foundation of using IR thermography for defect detection and characterisation is based on active thermography. In this method of inspection, an external excitation source is deployed for the purpose of stimulating thermal evolutions inside objects. The presence of sub-surface defects disrupts the evolution of electromagnetic pulse inside an object. The reflection of altered pulse at the surface can be recorded through thermal camera in the form of temperature anomalies. Through authors’ previous works, cold thermography has shown that it can be a viable defect detection alternative to the most commonly used means of active thermography, known as heating. In the current work, the characterisation of defect dimensions, i.e., depth and diameter, has been explored. A simple analytical model for thermal contrast over defect is used in order to approximate the defect depth and diameter. This is achieved by comparing the similarities of the model and the experimental contrast time-series. A method of time-series similarity measurement known as dynamic time wrapping (DTW) is used to score the similarity between a pair of model and experiment time-series. The final outcome of the proposed experimental setup has revealed that there is a good potential to predict the metal loss of up to 50% in mid-thickness substrate even by deploying a less accurate nonradiometric thermal device and no advanced image processing.

Investigation the structure and properties of deformed semi-finished products produced from chips of Al–Mg alloys system alloyed with scandium

The article presents the results of studies that make it possible to solve the problem of processing secondary waste from expensive aluminum alloys without irretrievable loss of metal. For this purpose, tasks were set and solved for the development of technological schemes for obtaining longish deformed semi-finished products from chip waste of Al–Mg alloys 01570 and 1580 alloyed with scandium using methods of powder metallurgy and metal forming. For their experimental verification, the operations of chip briquetting, combined rolling-extrusion (continuous extrusion), sectional rolling, hot extrusion and drawing in combination with heat treatment were applied. According to these schemes, semi-finished products in the form of rods and wires were obtained. Structure and mechanical properties were investigated. It has been revealed that when hot-extruded rods are obtained from chip briquettes of alloy 01570 on a vertical hydraulic press, even with significant degrees of deformation during extrusion, the margin of plastic properties is small and makes it possible to obtain a wire with a diameter of only 4.2 mm after drawing. The processing of briquettes from 1580 alloy chips using the combined rolling-extrusion method makes it possible to obtain after cold deformation a wire with a diameter of up to 3 mm. At the same time, the influence of the annealing process on the structure and properties of deformed semi-finished products from the investigated alloys was studied. It is shown that due to the low plasticity of the investigated material cold working of the rods must be carried out with small degrees of deformation, alternating it with intermediate annealing according to the proposed regime. An analysis of the physical and mechanical properties of the wire obtained using combined processing showed that its strength and plastic properties are comparable to the properties of the wire obtained from a cast billet, and the structure is characterized by a high degree of elaboration and compactness. Thus, as a result of the research, technological schemes have been developed and processing parameters have been determined for the production of rods and wire from graded chip waste of alloys 01570 and 1580 using compaction, discrete and continuous extrusion, as well as cold drawing.

Pore-scale numerical simulation of the heat transfer and fluid flow characteristics in metal foam under high Reynolds numbers based on tetrakaidecahedron model

In this paper, the pressure drops and interfacial heat transfer coefficient in metal foam with different pore density which was constructed by tetrakaidecahedron models were numerically studied under high velocity by Computational Fluid Dynamics (CFD). The velocity fields, temperature fields and pressure fields in the computational domain of metal foam were investigated. The equation of pore density and hydraulic diameter of metal foam was obtained. Influence of flow rate on the whole porous zone was also studied and obtaining the fitting formula to predict pressure loss in porous metal which was applied to the pore density range from 10PPI(Pore Per Inch)to 40PPI at high flow rate. Comparing with the previous literatures, the maximum error of pressure drop value was 12.23%. Meanwhile, the relationship between Reynolds number and interfacial heat transfer coefficient was studied, the results shown that the values of heat transfer coefficient increase with the rising of Reynolds number, but the lifting rate decreases gradually. And according to the data points, the numerical formula of interfacial heat transfer coefficient in porous metal was obtained which had a great correctness through contrasting with other data. As a result, the fitting formula could accurately predict the convection heat transfer coefficient of the metal foam interface and provide relevant data for the Thermal Non-equilibrium Model.

Extraction of metals from nickel concentrate via FeCl3·6H2O chlorination followed by water leaching and the preparation of (Ni,Cu)Fe2O4 catalyst

The traditional high-temperature smelting process of nickel sulfide concentrate has highlighted some problems, such as large loss of valuable metals, reduced economic benefits, and unclean production. Herein, a clean process of low-temperature chlorination roasting and water leaching was proposed to co-extract Ni, Cu and Co from low-grade nickel sulfide concentrate. The important factors such as concentrate particle size, roasting temperature, roasting time and chlorination agent dosage affecting the extraction of valuable metals were systematically studied, and 93.5 % Ni, 90.3 % Cu and 88.7 % Co were extracted under the optimal conditions. The thermal analysis kinetics of the chlorination process were investigated based on the differential thermal and thermogravimetric analysis (TG- DTA) combined with Kissinger method and Flynn-Wall-Ozawa (FWO) method. The results show that the apparent activation energy (Ea) of the chlorination process of the metallic minerals is 65.8 kJ⋅mol−1 and the kinetic equation can be expressed as dαdt=1.0×107exp-65,800RT1-α1.6. The (Ni,Cu)Fe2O4 (NCF) photocatalyst was prepared from leaching solution using α-Fe2O3 as a carrier to composite with other valuable metals, the photocatalytic degradation rate of which to the MB solution could reach 99.7 % within 150 min. The NCF composites could retain its photocatalytic efficiency for at least four cycles of reaction under visible light irradiation.

Low threshold and wavelength tunable SPASER based on plasmonic coupled nanostructure

We propose a low threshold and wavelength tunable plasmonic coupled nanolaser based on a plasmonic coupling between Au nanosphere and Au film. By the finite-element method, we investigate the optical properties of the plasmonic coupled nanolaser with different nanosphere diameters and gap distances between Au nanosphere and Au film. The optical cross section of the plasmonic nanolaser based on the coupled nanostructure can be 60 times larger than that based on an independent Au nanosphere. And the corresponding gain threshold of the plasmonic coupled nanolaser is only 35% of that of the nanolaser with the independent Au nanosphere. This is attributed to that the coupled nanostructure exhibits a stronger electric field and optical intensity than the independent Au nanosphere, it can more effectively improve gain to compensate for metal loss. In addition, the plasmonic coupled nanolaser also exhibits a wavelength tunability in a wide spectral range by controlling the Au nanosphere diameter and gap distance between Au nanoparticle and Au film. This work can provide us an effective way to develop the on-chip application of nanolaser.

On the quantitative assessment of corrosion damages of aluminum at the early stages using confocal laser scanning microscopy

Despite being widely used in such industries as chemical, aviation and food ones, aluminum and its alloys are known to be prone to localized corrosion, and this remains a problem to be solved, especially when it comes to pitting corrosion. Therefore, there is a necessity to detect traces of corrosion at the earliest stages and to quantify the extent of corrosion damage. The simplest solution for assessing the overall corrosion rate is to use the gravimetric method, which, however, does not provide information for assessment of localized corrosion. This paper is devoted to the consideration of the possibilities of using the method of confocal laser scanning microscopy (CLSM) for assessing corrosion resistance using high-purity aluminum. The CLSM method, due to its high resolution (especially along the vertical axis), enables to obtain quantitative data on the volume of corroded metal, determine the depth of corrosion damage including building their profilograms, and analyze the morphology of the surface damaged by corrosion. Owing to the high sensitivity of the CLSM method, corrosion losses were detected within 21 days, contrary to the standard gravimetric method, which failed to determine the loss of metal even after 160 days of corrosion testing.

Impact of the additive manufacturing process on the high-temperature corrosion of 316L steel in the presence of NaCl–KCl–ZnCl2 molten solar salt

A comparative study of the high-temperature oxidation and corrosion resistance of wrought and additive manufacturing selective laser melting (SLM) 316L stainless steel was performed in presence of molten NaCl–KCl–ZnCl2 salt used for thermal energy storage in the new generation of concentrated solar plants. Isothermal tests at 650 and 700 °C in a dry air atmosphere were conducted to evaluate (i) the effect of the manufacturing process and (ii) the effect of molten salts on the corrosion behavior of the steel by dimensional metrology analysis, scanning electron microscopy and X-ray diffraction characterization. The manufacturing process had a significant influence on the oxidation resistance. The wrought samples had a mass gain after 48 h that was four times greater than that of SLM samples at 650 °C, and 50% greater at 700 °C. The presence of the salt primarily increased the corrosion rate of all the samples and, again, the wrought pieces suffered 13% and 6% more corrosion in terms of metal loss than the SLM ones at 650 and 700 °C, respectively. The presence of more pathways for Cr diffusion associated with a higher number of defects in the microstructure of the SLM sample, as dislocations and grain boundaries, facilitated the formation of Cr2O3 scales in the SLM sample, avoiding the intergranular attack shown in the wrought one.

A study of the potential gold recovery from the ores of the Altyn-Zhylga deposit

The study covers the Altyn-Zhylga gold deposit located in the Batken region of the Kyrgyz Republic. The purpose of this work is to study the potential gold recovery when using the traditional processing methods and to identify the need for further technological research. In terms of its main components, the ore of the deposit rates as sulfide gold- and silver-bearing ore, with copper as the associated valuable component. Its ore minerals are represented by chalcopyrite, bornite, covelline, arsenopyrite, and free gold. The main industrially valuable components are copper and gold, with silver and molybdenum regarded as potential associated products. The distribution of copper, gold, and silver by size classes is mainly proportional to the yields of each class. However, a slight increase in gold, copper, and silver in the classes below 0.25 mm was noted in the sample. The processing technology for this ore was developed using gravity concentration methods as these enable the removal of free, coarse gold and silver, their parts associated with sulfides, and associated copper minerals from the process, which ensures that the resulting processing tailings have stable metal grades. Gravity concentration (using a gravity concentration table or a Knelson centrifugal separator) yielded a copper concentrate containing gold and silver with the recoveries of 76.6 % for copper, 38.1 % for gold, and 14.4 % for silver. The copper, gold, and silver grades in the gravity tailings are high, therefore the tailings are not final. In order to reduce metal losses, these tailings require further processing using other methods.

Stabilizing the Unstable: Chromium Coating on NiMo Electrode for Enhanced Stability in Intermittent Water Electrolysis.

Hydrogen production through water electrolysis is a promising method to utilize renewable energy in the context of urgent need to phase out fossil fuels. Nickel-molybdenum (NiMo) electrodes are among the best performing non-noble metal-based electrodes for hydrogen evolution reaction in alkaline media (alkaline HER). Albeit exhibiting stable performance in electrolysis at a constant power supply (i.e., constant electrolysis), NiMo electrodes suffer from performance degradation in electrolysis at an intermittent power supply (i.e., intermittent electrolysis), which is emblematic of electrolysis powered directly by renewable energy (such as wind and solar power sources). Here we reveal that NiMo electrodes were oxidized by dissolved oxygen during power interruption, leading to vanishing of metallic Ni active sites and loss of conductivity in MoOx substrate. Based on the understanding of the degradation mechanism, chromium (Cr) coating was successfully applied as a protective layer to inhibit oxygen reduction reaction (ORR) and significantly enhance the stability of NiMo electrodes in intermittent electrolysis. Further, combining experimental and Molecular Dynamics (MD) simulations, we demonstrate that the Cr coating served as a physical barrier inhibiting diffusion of oxygen, while still allowing other species to pass through. Our work offers insights into electrode behavior in intermittent electrolysis, as well as provides Cr coating as a valid method and corresponding deep understanding of the factors for stability enhancement, paving the way for the successful application of lab-scale electrodes in industrial electrolysis powered directly by renewable energy.

Immobilization of trace elements and lettuce growth in soil amended with activated dolomite phosphate rock fertilizers

Activation of low-grade phosphate rocks such as dolomite phosphate rock (DPR) with organic molecules of humic acid (HA) and sodium lignosulfonate (SLS) holds promise for developing slow release P fertilizers. Consequently, activated DPR fertilizers also contains multiple essential plant elements, including P, Ca, Mg, Zn, and Fe, while minimizing leaching losses of nutrients and heavy metals. Greenhouse experiments were conducted to examine the availability of Ca, Mg, and trace metals in soils applied with activated DPR fertilizers and subsequent response of lettuce (Lactuca Sativa L.) as compared with original DPR and water-soluble P fertilizers including superphosphates (SP) and diammonium phosphates (DAP). Application of activated DPR fertilizers stimulated the uptake of Ca, Mg, Zn, Fe, B by lettuce plants relative to original DPR and DAP. Potential toxic elements such as Cr, Cd, Ni, Pb, and Cu were mostly immobilized in soil without uptake by lettuce when applied with activated DPRs primarily due to increased soil pH, as compared with water soluble fertilizers such as DAP and SPs. Apparently, the activated DPR fertilizers offer advantages over original DPR materials and water-soluble P fertilizers in providing multiple nutrients with minimal adverse effects on soil and environmental quality.

PHYSICOCHEMICAL EVALUATION OF SOME TALC MINERAL DEPOSITS COLLECTED FROM FOUR STATES IN NIGERIA

This paper presents the analytic comparison of the physicochemical properties of talc mineral deposits present in some states in Nigeria with the intent of providing insight to the mineral composition of the talc deposit. Samples of talc mineral ore collected from Abaji, Abuja (ABS), Kagara, Niger state (KGS), Kebbi state (KBS) and two samples were obtained from Isanlu, Kogi state (Kogi brown and Kogi grey), were analysed via X-Ray Florescence XRF for metal oxides composition, bulk density, pH, solubility, acid solubility, moisture content and loss on ignition. The result of the metal oxides composition analysis indicates the presence of SiO2 in the range between 67.27, and 53.45%, MgO is present between 21.77, and 27.68%, sample KBS being the highest and KGS the lowest. Fe2O3, in the range 2.08, 11.60 and 10.23, 11.03 and 5.86% with sample KGS having the highest content and KBS lowest. Al2O3 is present between 1.00 -2.64%. In all the samples while metal oxides such as CaO, P2O5, SO3, TiO2, K2O, Cr2O3, NiO, MnO are present in traces between 0.09 to 0.3%. The pH of the samples is in the range of 6.97-7.54, bulk density is between 0.8013- 1.390g/cm-3, the moisture content is in the range of 0.1-0.6%. Loss on ignition is 3.756 -5.370%. The results showed that the Kebbi sample has higher purity than the samples from Niger, Kogi states and Abuja.

A Novel Crack Quantification Method for Ultra-High-Definition Magnetic Flux Leakage Detection in Pipeline Inspection

Cracks that may cause pipeline cracking and leakage become the main risk of in-service pipelines after conventional metal loss defects have been detected. Therefore, it is imperative to develop ultra-high-definition magnetic flux leakage (MFL) detection for cracks. Due to the larger spatial sampling interval of conventional MFL inspections than the crack defect width, sparse sampling will result in problems such as missed detection of crack defects or insufficient signal sampling of crack defect MFL signals. To address the problem, this paper presents a detection topology in which the magnetic field signal is integrated first and then sampled, and it can effectively sample the leakage magnetic field of cracks. Furthermore, a magnetic field spatial integration (MFSI) method is proposed based on the magnetic dipole model, which develops an analytical solution for the depth quantification of crack defects. Using the multi-MFL spatial integral values under different lift offs, iterative equations are constructed, and the numerical solution for the width quantification of crack defects is provided. The finite element simulation and physical experiment are constructed. And, the results show that the proposed MFSI method can realize the quantification of crack size. When the crack defect aspect ratio is greater than 4, the quantization error of the crack depth and width does not exceed 0.7 mm and 0.1 mm, respectively. The robustness of the MFSI method for crack quantification is also discussed and verified. Moreover, based on theoretical analysis and simulation data, this paper concludes that the distribution of cracks MFL signal is width-insensitive, which would cause that classic MFL opening profile recognition methods for metal loss defects are no longer applicable to crack defects. Therefore, the proposed MFSI method is useful and meaningful for crack defect quantification in ultra-high-definition MFL detection.