Mild Steel Specimens Research Articles

A novel route of carburizing through microwave hybrid heating

Abstract Carburizing is a surface treatment process by diffusing carbon into the steel. These days, manufacturing industries demand highly efficient processes that consume low power. Microwave processing is a newly evolving process that consumes low power. This study proposes a novel route for carburizing mild steel (substrate) through experimental and simulation studies using a microwave heating. Charcoal powder was used as a susceptor to convert microwave energy into heat energy and to deposit carbon on the surface of the specimen. The mild steel specimens were exposed to the microwave power input of 900 W and 360 W for exposure time of 1500 s and 1980 s naming it as S2 and S3 respectively. The microstructural analysis of specimens S2 and S3 confirms the formation of pearlite structures at the surface. However, the amount of pearlite structure was significantly higher for the S3. The higher carbon content is confirmed through energy-dispersive x-ray spectroscopy (EDS) analysis of specimen S3. The average hardness of the S3 specimen was determined to be 220.8 HV, which shows an increase of 38.36% compared to the S1 (base metal). x-ray diffraction (XRD) results indicate the additional cementite peaks (Fe3C) and ferrite-confirming phase transformations for carburized samples. The wear analysis of S2 and S3 was conducted through pin-on-disk testing. The peak COF of 0.73 and 0.64 was observed for S2 and S3 respectively. The hard surface of S3 resists the penetration of the counter body to a greater extent due to the fine morphology of pearlite. From the FEM study, the maximum value of 7.96 × 10 3 (V/m) was determined at the center region for the electric field distribution in the microwave cavity, which is the optimum value for efficient heating. The maximum temperature of the mild steel obtained during the carburization process was 900 °C in 1800 s. The microwave carburizing process requires relatively less time than the conventional carburizing process which will save energy consumption.

An experimental investigation of abrasive jet machining parameters for optimized surface finish of mild steel components

Abrasive jet machining is one of the unconventional machining processes that are initiated for alternations of surface characteristics of ductile materials, like mild steel, due to the entrainment of high-velocity abrasive particles. The present experimental investigation deals with the major process parameters of the AJM process, namely air pressure, standoff distance, and time of machining, on the average surface roughness (Ra) of mild steel specimens. Experiments were conducted on the self-developed AJM setup using aluminum oxide abrasive particles of an average size of 50 µm. The pressure of air is changed in three levels, 6, 7, and 8 bars. The standoff distance is taken as 2 mm constant for all the cases. The surface roughness was measured at machining times of 20, 40, and 45 seconds. The presence of the increase of air pressure from 6 to 8 bars applied for all the machining time showed an increasing influence on roughness, although always significant in Ra. For 8 bars of pressure and 45 s of machining, the minimum resulted in 1.39 µm, compared with 3.47-4.02 µm. The rate of decrease in surface roughness is sharp with increasing machining time from 20 to 40 seconds but marginal beyond that. An optimal machining time of 40–45 seconds was identified to obtain a minimum Ra. Capability of AJM as an effective technique to enhance the surface finish of mild steel components, and practical insight of this study is very useful toward optimization of process parameters for attaining the targeted surface quality. The results obtained may assist in expanding the industrial application of AJM toward the finishing of ductile materials in various manufacturing fields.

Examining Shape Dependence on Small Mild Steel Specimens during Heating Processes.

With regard to the heating technology of small test specimens (D < 1 inch, i.e., 25.4 mm), only a limited amount of data and literature are available for making adequate technological decisions. Heating time of small geometric shapes is influenced by the technological parameters of the furnace, the temperature, the disposition technique in the furnace and the geometric characteristics of the workpiece. How to shorten heating time to achieve a suitable material structure is a vital question, while considerable energy is saved at the same time. Among the geometric characteristics, shape dependence is one of the important aspects that must be taken into account in terms of heating technology. Shape dependence is usually taken into account with empirically produced correction factors, which can result in significant oversizing of heating time, energy-wasting technology and material structure of insufficient fineness. In the course of our work, we investigated and compared the shape dependence of cylindrical and prismatic specimens with the same surface-to-volume ratios, which were combined with surface heat transfer analyses and geometric effect tests to formulate new approximate equations for determining heating time. As a result, we could mathematically derive a relationship between heating time, size and shape of the active surfaces, the correlation of which can shorten heating time by 20%. In addition, a shape factor (1.125) between cylinder and prismatic-shaped specimens was determined, which can be used with the new equation to calculate heating time for similar specimens. At last, a relationship is developed between the amount of heat that can be stored in the body during heat equalization and the complexity of the shape, which can be characterized through ratios depending on heating times and active surfaces in the function of total surface/volume ratio. Based on this relationship it can be determined more precisely when heat equalization occurs; therefore, shorter heating time can be achieved. In conclusion, with the help of this new method, optimal heating time for structural steel components, in the case of small cross-section and weight, can be determined.

Production and characterization of low-density silicon nitride reinforced zinc nanocomposite coatings on mild steel for applications in marine and automotive industries

In today's automotive, marine and petrochemical industries, the desire for lightweight materials has increased. Hence, necessitating the production of components with low density. In this work, lightweight Zn–Si3N4 coatings were developed by including Si3N4 in the zinc matrix. The optimal coatings were produced on steel samples at 45 °C and varied Si3N4 particles and voltages following ASTM A53/A53M standard. The deterioration (corrosion) property i.e. corrosion rate (CR) and current density (jocorr) of the uncoated (control) and coated samples were examined in 0.5 M of sulphuric acid using a potentiodynamic polarization technique following ASTM G3/G102 standard. The microstructure of the samples was studied via the SEM micrographs and XRD patterns, while the wear performance resistance (following ASTM G99 standard) and electrical conductivity of the samples were examined with a pin-on-disc tribometer and ammeter-voltmeter. The corrosion experiment indicated that the uncoated mild steel specimen possessed a CR of 12.345 mm year−1 and jocorr of 1060 μA/cm2, while the CR and jcorr of the coated samples ranged from 2.6793 to 4.7975 mm year−1 and 231−413 μA/cm2, respectively. The lower CR and jcorr values of the coated specimens, relative to the coated sample showed that the coatings possessed superior passivation ability in the test medium. The SEM micrographs of the samples showed refined morphology, while the XRD patterns revealed high peak intensity crystals such as Zn4SiN, ZnNSi, Zn4N and Zn2NSi, which could be beneficial to the mechanical properties and corrosion resistance of the steel. Moreover, the wear resistance study indicated that the COF of the uncoated sample ranged from 0.1 to 0.5, while those for coated specimens ranged from 0.05 to 0.35. Similarly, the uncoated steel exhibited a wear volume (WV) of 0.00508 mm3, while the WV of the coated specimens ranged from 0.00266 to 0.0028 mm3, indicating the existence of high strengthening mechanisms between the interface of the protecting device and the steel. Also, the electrical conductivity of the mild steel sample reduced from 12.97 Ω−1cm−1 to 0.64 Ω−1cm−1, indicating that the electrical resistivity of the steel was enhanced by the coatings.

Investigation of Garcinia kola Exudates as Corrosion Inhibitor for Mild Steel in Acidic Environment

This study investigated the performance of Garcinia kola exudates in preventing mild steel exposed to acid concentrated water and soil. The study was performed in order to find an alternative coating substance that can reduce the corrosion of mild steel pipes exposed to corrosive water and soil media. Various mild steel specimens were cut into portions and coated with the exudates at 25 - 50µm thickness. To accelerate the rate of corrosion, 0.5M hydrochloric acid (HCl) was added to tap water in a container. Also, the same concentration of HCl was equally added to soil samples. Uncoated mild steel specimens were immersed in the acid concentrated water and soil, servicing as control sample. The rate of corrosion was monitored for 30 days (720 hours). The inhibition efficiency of the exudates for both corrosive media was compared. Results showed that the weight loss and corrosion rate of mild steel decreased with increase in coating thickness. Comparatively, weight loss and corrosion rate in the uncoated specimens were higher than the coated specimens. For uncoated specimens, the corrosion rate was 0.2793mm/yr and 0.4150mm/yr for specimen immersed in water and soil respectively, but at 25µm coating thickness, it decreased to 0.01369mm/yr and 0.2870mm/yr for specimens in water and soil. Also, at 50µm coating thickness, corrosion rate decreased to 0.0052mm/yr and 0.0318mm/yr for specimens in water and soil, respectively. The inhibition efficiency increased with coating thickness, ranging from 51.00 – 98.15% for specimens immersed in water and 30.84 – 92.33% for specimens buried in soil at 25µm – 50µm coating thickness. The results demonstrated that Garcinia kola exudates can be used as corrosion inhibitor for mild steel exposed to corrosive media.

Impact of the Delay Period between Electrochemical Hydrogen Charging and Tensile Testing on the Mechanical Properties of Mild Steel

With escalating global regulatory pressure for countries to adhere to emission laws, repurposing existing natural gas pipelines for hydrogen-based commodities stands to be an economical solution. However, the effects of hydrogen embrittlement must be thoroughly considered for this application to avoid the unexpected catastrophic failure of these pipelines. The literature proposes several physicochemical embrittlement models. This paper reports one aspect of hydrogen embrittlement that remains to be quantified: the recovery of ductility (embrittlement) of mild steel specimens subjected to artificially accelerated hydrogen absorption via electrochemical charging as a function of time. The effects of charging duration and particularly the delay period between charging and mechanical tensile testing were investigated. Unsurprisingly, longer charging time shows a greater loss of elongation; however, a more extensive recovery of ductility correlated with longer charging time in the first few days after charging. The data also show that while the uncharged mild steel met all minimum required values for strength and elongation for the specified grade, there was a substantial variability in the elongation to failure. The same trends in variability of elongation translated to the hydrogen-charged specimens. Due to this extensive variability, failure to meet the elongation specification of the grade is reported based on the worst-case scenario obtained for a given set of samples for each exposure condition. These results have practical implications for the monitoring and testing of infrastructure exposed to hydrogen, particularly as this relates to industry planned operational shutdown schedules.

High‐potent trifunctional polybenzoxazines coatings for superhydrophobic cotton fabrics and mild steel corrosion protection applications

AbstractNew trifunctional polybenzoxazines were developed and utilized as a high‐potent coating material for superhydrophobic cotton fabrics and mild steel corrosion protection applications. New trifunctional benzoxazines resin have been synthesized using trihydroxytriphenylmethane (TTM) with dimethylaminopropylamine (dmapa), 1‐(3‐aminopropyl)imidazole (ipa) and aminoethoxyethanol (aee) as amine sources with paraformaldehyde through Mannich condensation. The structural confirmation of synthesized benzoxazines was ascertained by spectral studies. The ring opening polymerization of TTM‐Bzs was studied using DSC analysis. All the three TTM‐Bz monomers show curing temperature lower than 210°C. The thermo‐stability and water contact angle (WCA) of polybenzoxazines were studied using thermogravimetric analysis and goniometer, respectively. Among the TTM‐PBz studied, the poly(dmapa) exhibit better thermo‐stability and hydrophobic behavior when compared to rest of the synthesized polybenzoxazines. Poly(TTM‐dmapa)‐coated cotton fabric exhibits the superhydrophobic behavior and mild steel (MS)‐coated specimen possesses the higher charge transfer resistance value of 3.47 × 107 Ω cm2. It was also inferred that all the TTM‐PBz‐coated MS specimens exhibit higher corrosion protection behavior as well as good thermo‐stability and hydrophobic nature. Further, the obtained results suggested that these materials can be suitably exploited for hydrophobic anticorrosion applications with improved performance and enhanced longevity.

Carboxylated cellulose nanofibrils based on banana rachis as additive in oil-based emulsion coolant for effective flank wear reduction in lathe operation

Nitro-oxidized carboxylated cellulose nanofibrils (NOCNFs) from the banana rachis are employed in oil-emulsion coolant as an additive. The concentrations of NOCNF were 0.1, 0.2, 0.3 wt. %. The cutting parameters include the spindle speeds and depth of cut. The temperature and wear reduction were significant. The temperature at the tool flank decreased from 119°C to 76°C, corresponding to an 11% reduction in wear at the depth of cut co. 2 mm and spindle speed of 1330 rpm. The viscosity of the nanofluid and the corrosion of the low-carbon mild steel specimen are discussed. Arguably, a stable NOCNF nanofluid suspension is good against wear even at elevated temperatures. Interestingly, these results occurred at a lower NOCNF concentration co. 0.3% wt. compared to 1–2 wt. % from Al2O3 nanoparticles in literature. In this paper, banana rachis nanofibrils are attractive for developing of effective and environmentally friendly additives from biomass.

Effects of Welding Techniques on the Corrosion Resistance of Mild Steel

The performance and longevity of welded structures depend heavily on corrosion resistance, particularly when mild steel is used as the primary material. The paper provides an overview of the investigation of the influence of various welding techniques on the corrosion resistance of mild steel. The study combines mild steel specimens using spot-welding, gas metal arc, and electric arc welding techniques. Electrochemical and immersion testing techniques are used to assess the welded samples' resistance to corrosion. The impact of metal microstructure, welded zone surface characteristics, corrosion rates, and filler material selection on corrosion resistance is examined. The results demonstrate that the choice of welding process has a significant effect on mild steel corrosion resistance. Some techniques have a higher level of corrosion resistance owing to the use of heat. As exposure duration rises, both diluted and concentrated hydrochloric acids cause weight loss in the absence of an inhibitor. The temperature increased over time until 190 minutes, which resulted in a decrease in temperature efficiency. In the impact test, adding 3%, 6%, and 9% of the welded components to the metal alloy increased the impact's energy output from 12.32 J to 12.69 J, 12.99 J, and 13.51 J, respectively. The energy effect of the reinforced mild steel was reduced owing to the brittleness of the welded parts relative to the ductile metal matrix. The composite absorbs impact stresses, and the enhanced weight ratio of the welded mild steel thereby increases its toughness.

Numerical Investigation of Tensile and Compressive Behavior of Mild Steel Subjected to High Strain Rate

Numerical simulations were conducted to validate computational and constitutive models for steel materials through dynamic material tests involving both tension and compression. These simulations involved the numerical modeling of the split Hopkinson pressure bar (SHPB) apparatus, with the appropriate loading applied directly in compression and indirectly in tension. To induce a tensile wave within the specimen, a shoulder, such as a coupler or collar, was interposed between the bars. The simulations were carried out using the LS-DYNA finite element code. In these numerical simulations of the SHPB tests, the MAT-15 Johnson–Cook material model was applied to represent mild steel. The resulting stress–strain relationships obtained under both compression and tension conditions were subsequently compared to corresponding experimental data. The primary objectives of these simulations were to determine the optimal placement of strain gauges on both the input and output bars of the tensile SHPB setup. Additionally, the simulations aimed to assess the influence of the gauge length-to-diameter ratio on the behavior of the mild steel specimen subjected to dynamic tension and compression. The results showed that the pulse produced due to the mechanical mismatch of the element at boundaries can be avoided using the length of the input bar smaller than the output bar. Further, the location of the strain gauge in the case of the output bar should be toward the output bar-shoulder interface, while in the case of the input bar, it should be considered at the center of the span of the bar.

Comparative analysis of abrasive wear between aluminium alloy and mild steel in a pin-on-disc tribological test

A comparative analysis of the abrasive wear of aluminium alloy and mild steel on the pin-on-disc wear test machine has been successfully carried out. An investigation on the effects of wear, stress and strain on the aluminium alloy and the mild steel was conducted. The wear test carried out determined the difference between rate of wear of the aluminium alloy and the mild steel. The input parameters applied in determining the wear rate were time of wear, sliding distance, track diameter of the disc and mass difference before and after the experiment. The finite element analysis developed the stress and elastic strain distribution obtained on the application of 2 kg load (20 N) on the aluminium alloy and mild steel specimen. The equivalent (Von Mises) stress distribution in mild steel had a maximum stress value of 0.023625 Mpa and minimum stress of 1.444×10-5 Mpa while that of the aluminium alloy yielded a maximum and minimum stress of 0.0365 Mpa and 8.5×10-5 Mpa respectively. It was evident that the aluminium alloy recorded a higher magnitude of stress than the mild steel. This showed that the aluminium alloy being relatively light was more stressed than the mild steel. It was discovered that the rate of wear was higher in the aluminium alloy than in the mild steel.

An experimental and theoretical investigation of corrosion inhibitive behaviour of 4-amino antipyrine and its schiff’s base (BHAP) on mild steel in 1 M HCl solution

Corrosion inhibitive behaviour of 4–aminoantipyrine (AAP) and its Schiff base 4 – ((4–bromo-2–hydroxybenzylidene)amino)–1,5–dimethyl–2–phenyl–1H–pyrazole–3(2H)-one (BHAP) derived from 4–aminoantipyrine and 4-bromosalicylaldehyde has been investigated on mild steel specimen in 1 M HCl solution using potentiodynamic polarisation (PDP), EIS (electrochemical impedance spectroscopy). The AAP and BHAP compounds were synthesized by green, eco-friendly magnetic nanocatalyst, which can be further reused. Moreover, the previously reported catalysts are inorganic which are hardly degraded, while organic compound-based corrosion inhibitors are biocompatible. SEM (scanning electron microscopy) micrographs and Gravimetric measurement (weight loss) indicate that the rate of corrosion decreases with an increase in the concentration of inhibitor. The obtained result shows that 200 ppm BHAP has a maximum efficiency of 93.9%, while AAP has a slightly lower efficiency of 81%. The adsorption of BHAP on a mild steel surface followed the Langmuir adsorption isotherm and was found to involve chemisorption. Further insight into the mechanism of interaction of BHAP molecules with mild steel was obtained by Density Functional Theory (DFT).

Comparative study of polyanthranilic acid and sulphonated polyaniline on the mild steel corrosion in aqueous hydrochloric acid

ABSTRACT Investigation of corrosion in mild steel specimens, using 0.5 N muriatic acid mixture with PANA and SPANI conducting polymers, has been done using Weight Loss (WL), Electrochemical Impedance Spectroscopy (EIS), Potentiodynamic Polarization (PDP), and Surface Morphology. The highest Inhibitor efficiency (IE) reported at 70 ppm for PANA was 86.18%, whereas 89.2% for SPANI, at a temperature of 35±1°C, under 3 h duration. Both polymers exhibit synergistic inhibitor actions at low acid concentrations and temperatures, indicating effective adsorption of polymers on the specimen surface and are seen to satisfy the Langmuir adsorption isotherm and follow cathodic and anodic types of properties. The estimated synergism value is unity, which is only attributed to a synergy that the higher IE in both polymers is achieved by adding surfactants. AFM supports all the above evaluation results. The results conclude that SPANI shows much better characteristics than PANA for the conditions examined.

Flame-retardant and anti-corrosion behaviour of cardanol-based polybenzoxazine composites

A new monomer of bi-functional benzoxazine was synthesised using cardanol (C) and p-phenylenediamine (ppda) under suitable experimental conditions. The curing behaviour of the cardanol-based 1,4-bis(7-pentadecyl-2H-benzo[1,3]oxazin-3(4H)-yl)benzene (C-ppda) benzoxazine monomer was studied by differential scanning calorimetry analysis, and the polymerisation temperature (T p) of C-ppda benzoxazine was found to be 237°C. Further, the benzoxazine monomer was reinforced with varying weight percentages (5, 10 and 15 wt%) of bio-ash derived from Aerva lanata (AL-ash) to obtain hybrid composites. Thermogravimetric analysis data indicate that AL-ash-reinforced benzoxazine composites possess excellent thermal stability and a flame-retardant behaviour. The morphology of AL-ash- and cardanol-based benzoxazine composites was analysed using field emission scanning electron microscopy (FESEM). The FESEM results indicate homogeneous distribution of AL-ash in the composites. Energy-dispersive X-ray spectroscopy analysis was used to determine the elemental composition of the AL-ash used for the preparation of composites. The value of the water contact angle of poly(C-ppda) was found to be 148°. Data obtained from corrosion studies indicate that the mild steel specimen coated with a benzoxazine matrix and the specimen coated with bio-ash-reinforced benzoxazine composites exhibit an excellent resistance against corrosion. The bio-ash-reinforced composites of cardanol-based benzoxazine can be used in the form of sealants, encapsulants, adhesives, coatings and matrices in microelectronics and automobile applications under high thermal and moist environmental conditions.

Sustainable l-tyrosine based bio-benzoxazines for efficient protection of mild steel surfaces from marine environment

In the present work, a new type of bio-based tyrosine-dipeptide (TB) was successfully synthesized and it was converted into a structurally modified benzoxazine (TB-Bz) using three different amino compounds (aniline (a), dodecylamine (dd) and furfurylamine (ff)) and formaldehyde at appropriate reaction conditions. The molecular structure of these benzoxazines (TB-a, TB-dd and TB-ff) was elucidated using Fourier transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance spectroscopy. The curing behaviour and thermal stability of the benzoxazines were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) respectively. The ring opening polymerization of TB-a, TB-dd and TB-ff benzoxazines were observed at 222 °C, 231 °C and 233 °C respectively. Data obtained from thermal analysis, the char yield of corresponding polybenzoxazines (poly(TB-a), poly(TB-ff) and poly(TB-dd)) were observed at 43%, 51% and 25% at 850 °C respectively. The hydrophobic behaviour of poly(TB-a), poly(TB-ff) and poly(TB-dd) was ascertained from the measurement of water contact angle studies and the values obtained are 139⁰±2, 143⁰±2, 146⁰±2, respectively. The corrosion protection studies of the mild steel specimen surfaces were carried out using open-circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization. Among the mild steel specimens, coated with different benzoxazines, the poly(TB-ff) coated specimen was found to be less aggressive towards corrosion and possesses about 98.3% corrosion protection efficiency. The data obtained from different studies suggest that the bio-based tyrosine dipeptide benzoxazines developed in the present work can be considered as a better coating material for the protection of surfaces of mild steel against corrosion under adverse environmental conditions.

Exploring the Effectiveness of Isatin–Schiff Base as an Environmentally Friendly Corrosion Inhibitor for Mild Steel in Hydrochloric Acid

A recent study has shown that Schiff base OHMHI is an effective inhibitor of the corrosion of mild steel in acidic media. The study utilized weight loss measurements and electrochemical techniques, such as EIS and potentiodynamic polarization, to analyze the corrosion inhibition efficiency of OHMHI. The results of the study show that the presence of OHMHI in the corrosive environment significantly reduced the corrosion rate of mild steel and increased its corrosion resistance. The impedance spectra analysis indicated that OHMHI was adsorbed on the surface of mild steel, providing a protective layer. The potentiodynamic polarization study confirmed the protective role of OHMHI by showing an increase in the passive current density of the mild steel in the presence of OHMHI. The inhibitory efficiency of OHMHI was found to be 96.1%, indicating that it is an effective corrosion inhibitor for mild steel. The study also investigated the optimal conditions for the use of OHMHI as a corrosion inhibitor, with a concentration of 0.5 mM and a temperature of 303 K being chosen. The Langmuir adsorption isotherm concept was used to demonstrate the physical and chemical adsorption of OHMHI on the surface of mild steel. Morphological investigations of the uninhibited and inhibited surfaces of the mild steel specimen were examined using scanning electron microscopy (SEM) analysis. Furthermore, computational investigations using density functional theory (DFT) and experimental data were merged to explore the corrosion inhibition efficiency and mechanism of inhibition. Although the results are promising, further studies are needed to determine the long-term effects of OHMHI on mild steel corrosion and to evaluate its effectiveness under different environmental conditions. Overall, the study highlights the potential of OHMHI as an effective corrosion inhibitor for mild steel in acidic media.

Synthesis and Characterization of Sustainable Curcumin‐Based Bio‐benzoxazines for Antimicrobial and Anticorrosion Applications

AbstractIn the current study, three novel bio‐based benzoxazines were produced from curcumin (CU), which reacts individually with three different primary amines such aniline (a), furfurylamine (ffa) and octadecylamine (oda) under suitable experimental conditions. FTIR and 1H‐NMR spectra were used to confirm the molecular structure of synthesized curcumin based benzoxazine monomers (CU‐a, CU‐ffa and CU‐oda). It was found that the curing temperatures of the three benzoxazine monomers, CU‐a, CU‐ffa, and CU‐oda are 207 °C, 193 °C, and 199 °C respectively. According to theromogravimetric analysis (TGA) analysis, cured poly(CU‐a), poly(CU‐ffa), and poly(CU‐oda) have remaining char yields of 78, 77, and 55 %, respectively, and their corresponding limiting oxygen index (LOI) values are 49, 48, and 40, respectively, confirming that they have exceptional thermal stability and flame‐retardant qualities that are ideal for applications. The value of water contact angle of poly(CU‐a), poly(CU‐ffa) and poly(CU‐oda) are 131°, 135° and 137° respectively, which infer their excellent hydrophobicity. Results from corrosion and anti‐microbial studies ascertain that these curcumin based benzoxazines can be considered as efficient coating materials to protect the surfaces of mild steel specimen under adverse environmental conditions. Using density‐functional theory (DFT) band gap of the monomers has been calculated and found that CU‐a possesses the lower value of band gap of 2.9212 eV than other benzoxazines.

Biopolymer sodium alginate based titania and magnetite nanocomposites as natural corrosion inhibitors for mild steel in acidic medium

Green biopolymeric materials and its hybrid nanocomposites, i.e. sodium alginate grafted polymethylmethacrylate based titanium dioxide and iron oxide (SA-g-PMMA/TiO2 and SA-g-PMMA/Fe3O4) have been explored for the prevention of mild steel's corrosion in 15% HCl. It is reflected from the electrochemical impedance data that SA-g-PMMA/TiO2 exhibits maximum inhibition efficiency of 97.28% followed by SA-g-PMMA/Fe3O4 that gives 96.82% efficiency while the unmodified sodium alginate possess merely 84.74% efficiency. The declining trend of inhibition efficiency with rising temperature has been explained through gravimetric studies conducted at 303 K- 333 K. The thermodynamic activation and adsorption parameters revealed the mixed mode of adsorption of inhibitors over mild steel surface which follow Langmuir adsorption isotherm. It has been observed from tafel polarization studies that all studied inhibitors are mixed type in nature. The surface morphological inspection of the mild steel samples was done through FE-SEM and AFM, which revealed the formation of better protective adsorption layer over the exposed metallic surface by the nanocomposites in comparison to sodium alginate alone. In addition to this, the elemental composition of adsorbed film on inhibited mild steel specimens was obtained by XPS technique. Quantum parameters obtained through Density Functional Theory (DFT) further corroborate the experimental outcomes.

Compressive thermal wave imaging for subsurface analysis

Subsurface detail extraction in active thermography demands high capturing rates, resulting in less exposure time, data redundancy, large bandwidth requirement, and wastage of sensing resources and memory. Compressive sensing (CS) is a data acquisition technique that overcomes these limitations by acquiring the signal at sub-Nyquist rates with fewer measurements considering the signal is sparse in some transformed domains and reconstructing the original response. This paper validates the application of CS in frequency modulated thermal wave imaging by experimenting on a quick responsive mild steel specimen with artificially simulated back hole defects. The discrete cosine transform is selected as sparsity prior and the orthogonal matching pursuit is used to reconstruct the original thermal response from the compressed measurements. The initial analysis is carried out on choosing the optimal sparsity parameter and the number of measurements, followed by the effect of the number of measurements on defect detection in various post-processing techniques used in frequency modulated stimulus. The defects detected and their qualitative analysis through assessing signal-to-noise ratio confirmed the suitability of CS for efficient reconstruction of thermal data and thereby enhancing the defect signature.

Fracture characteristics and damage prediction in flat steel beams under contact explosions

Research to predict and mitigate local damage of steel elements subjected to contact and close-in explosion remains a topic of interest. In this study, the effects of charge mass, specimen geometry, and explosive charge position on the damage and fracture of flat, mild-steel specimens under contact charges are investigated. From macroscopic and microscopic observations of the fracture surfaces, rupture properties of the flat steel specimen under contact explosion are examined. Based on these observations, the rupture process of flat steel specimens under contact explosion is considered as follows: 1) the opposite surface of a blast -loaded specimen was damaged by spalling due to tensile stress wave, and 2) the rest of the cross-section of a specimen was stretched and ruptured by blast pressure into two pieces. On the microscopic fracture surface observed by a scanning electron microscope demonstrates cleavage, which is caused by brittle spalling and rupture. Their microscopic fracture surfaces are different based on charge positions, specimen thicknesses, and observation points. Furthermore, the effects of charge mass and specimen cross-section on damage to steel specimens under contact explosions are evaluated, and empirical equations to predict thickness limits are developed for spalling and rupture of flat, mild-steel specimens.