Aggressive Acidic Environments Research Articles

Evaluation of diethyl 4-(5-bromo-1H-indol-3-yl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate: synthesis, anti-corrosion potential, and biomedical applications

The pursuit of advanced multifunctional compounds has gained significant momentum in recent scientific endeavours. This study is dedicated to elucidating the synthesis, rigorous characterization, and multifaceted applications—encompassing anti-corrosion, antimicrobial, and antioxidant properties—of Diethyl 4-(5-bromo-1H-indol-3-yl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate. The 1,4-dihydropyridine derivative was meticulously synthesized through a strategic reaction of ethyl acetoacetate, ammonium acetate, and 5-bromoindole-3-carboxaldehydein the ethanol medium at 60 C. Subsequent spectral validations were conducted using sophisticated techniques, namely FTIR, NMR, and Mass spectrometry, resulting in data that perfectly resonated with the hypothesized chemical structure of the compound. Its anti-corrosive potential was assessed on mild steel subjected to an aggressive acidic environment, employing comprehensive methodologies like gravimetric analysis, Tafel polarization, and EIS. Concurrently, its antimicrobial prowess was ascertained against a spectrum of bacterial and fungal pathogens viz., Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas, Candida albicansandAspergillusniger, leveraging the disc diffusion method and using Gentamicin as a reference standard.The empirical results illustrated a substantial decrement in corrosion rates with ascending concentrations of the organic compound, achieving an apex of anti-corrosive efficacy at 81.89% for a concentration of 2 × 103 M. Furthermore, the compound outperformed Gentamicin in antimicrobial screenings, manifesting superior efficacy against all tested pathogens. The antioxidant potential, quantified using the DPPH free radical scavenging assay against ascorbic acid as a benchmark, was found to have an IC50 value of 113.964 ± 0.076 µg/ml.This comprehensive investigation accentuates the paramount potential of the synthesized dihydropyridine derivative in diverse domains—from industrial applications as a corrosion inhibitor to therapeutic avenues given its pronounced antimicrobial and antioxidant capabilities. The compelling results obtained pave the way for expansive research and development initiatives cantered around this multifaceted compound.Graphical

Sulfuric acid resistance behaviour of alkali-activated slag and waste glass powder blended precursors

The acid resistance of cementitious materials is an important property when exposed to aggressive acidic environments. In this study, the waste glass powder (GP) and slag as precursors were activated by alkali (Na or K)-silicates or by a combination of (Na or K)-silicates with air pollution control (APC) residues to produce alkali-activated materials (AAMs) and alkali/sulfate-activated materials (ASAMs). The compressive strength and volume change of the AAMs and ASAMs mortar were performed to understand the influence of sulfuric acid attack on the resulting performances. Meanwhile, the microstructure and micro-mechanics evolution were investigated by the nanoindentation technology. The results showed that the compressive strengths of all AAMs and ASAMs mortar decreased under a low pH solution. The Na- and K-AAMs mortar exposed to the acid solution shrank considerably even though a large amount of gypsum formed, while the Na- and K-ASAMs exhibited certain expansion behavior due to the existing sodium sulfate. Upon the sulfuric acid attack, the framework changes of the K-A-S-H/N-A-S-K caused by dealumination had less effect on the integrity than the dealumination and decalcification of the C(-A)-S-H gel. In comparing the alkali cations, the K-type activator impacted more positively than the Na-type activator for the performance development of the AAMs and ASAMs under the sulfuric acid attack. Moreover, the AAMs and ASAMs showed a buffering capacity of acid. This work provides a scientific reference value for applying the AAMs and ASAMs in real environments.

Electrochemical and theoretical investigations of favipiravir drug performance as ecologically benign corrosion inhibitor for aluminum alloy in acid solution

Aluminum–silicon alloys have become a preferred option in the automotive and aerospace industries thanks to their fault-tolerant process ability and reasonable static characteristics at relatively affordable costs. This study aimed to investigate the use of favipiravir (FAV) drug as a biocompatible and eco-friendly inhibitor to protect aluminum alloy (AlSi) surface in an aggressive acid environment (1.0 M HCl). The electrochemical measurements declare that FAV is categorized as an inhibitor of mixed type with a cathodic effect. At 100 ppm, FAV had the highest inhibitory efficiency (96.45%). FAV is associated with lower double-layer capacitance values and more excellent charge-transfer resistance. These results show that AlSi corrosion in 1.0 M HCl is reduced in the presence of FAV. The Langmuir model is well-suited to the FAV adsorption behavior (R2 ≈ 1). Chemisorption is the primary adsorption in this environment. The theoretical calculation studies corrosion inhibitors' molecular structure and behavior. Different quantum chemical properties of the FAV have been calculated, including energy difference (ΔE), softness, global hardness, and energy of back-donation depending on the highest occupied and lowest unoccupied molecular orbitals. In addition, Mulliken and Fukui’s population analysis and the Molecular Electrostatic Potential map represent the electron distribution and the molecule’s active centers. Experimental findings and quantum chemical computations matched, and FAV is recommended as a green corrosion inhibitor.

Performance evaluation of OPC mortar exposed to organic acid environments

Concrete structures are deteriorated everyday due to its widespread exposure to aggressive acidic environments. The main objective of the study is to evaluate the degradation kinetics of OPC mortar specimens exposed to various organic acids. Acetic acid, citric acid, lactic acid and propionic acid are the organic acids used for the experiment and the concentrations adopted are 5 %, 10 % and 15 % (w/v). The results show that specimens immersed in citric and lactic acids exhibits a higher degradation than that immersed in acetic and propionic acids. Specimens subjected to 15 % lactic acid solution have been completely disintegrated by 42 days of acid exposure.

Improving sulphuric acid resistance of slag-based binders by magnesium-modified activator and metakaolin substitution

Alkali-activated slag (AAS) is an appealing alternative to ordinary Portland cement (OPC) in aggressive acid environment considering its relatively low calcium content and potential in retarding aggressive media penetration. This study evaluates the effect of reactive MgO–NaOH mixture as an activator on the performance of AAS with and without metakaolin substitution upon sulphuric acid exposure. The experimental results reveal an improved acid resistance of slag pastes with supplementary magnesium and the improvement is further enhanced with 20% metakaolin substitution. The improved effect by supplementary magnesium is not only attributed to its microstructure refinement for retarding acid penetration; but also contributed by the acid neutralisation capacity of the formed brucite and the potentially positive effect of magnesium on stabilising the AAS binding gel. Stratified silica-rich gels are formed in the metakaolin-substituted AAS, whose formation is primarily attributed to the intrinsic difference of the formed aluminosilicate gels and related to the pH value and the presence of Mg2+. Considering the dense structure of these gels, they might act as protective barriers for the AAS upon acid deterioration.

Adsorption, electrochemical and theoretical studies on the protective effect of N-(5-bromo-2-hydroxybenzylidene) isonicotinohydrazide on carbon steel corrosion in aggressive acid environment

Adsorption, electrochemical and theoretical studies on the protective effect of N-(5-bromo-2-hydroxybenzylidene) isonicotinohydrazide on carbon steel corrosion in aggressive acid environment

Corrosion Protection in Acidic Medium for Mild Steel Using Various Plants Extract as Green Corrosion Inhibitor - A Review

Acidic solutions is widely adapted in industries for various operations whereas green corrosion inhibitors is used for the elimination of corrosion / deposition of scales. By using inhibitors, control of metal corrosion occurs in aggressive environment. Various types of natural composites were designed for finding out corrosion inhibition efficiency. Organic compounds possessing nitrogen, sulphur and oxygen exposed excellent inhibition effectiveness. Nevertheless, large number of natural compounds have toxic effect on environment as well as on living organism. Hence, it is necessary to point out cheap, easily available, biodegradable and eco-friendly inhibitor to corrosion with high inhibition efficiency. This article deliberates the properties of inhibitor, adsorption mechanism of inhibitor, inhibition mechanism and inhibitor efficiencies of plant extract in aggressive acidic environment.

Superior Corrosion Resistance of Ti-Al-Zr Alloy in Aggressive Nitric Acid Environments

This paper describes the corrosion behavior of a Ti-based alloy, Ti-Al-Zr for aggressive nitric acid applications. Corrosion behavior of the materials was established using electrochemical polarization technique, for three process variables encountered in reprocessing plants: (a) nitric acid (1, 3 and 6 M), (b) temperature (25 and 75 °C) and (c) oxidizing ions (Ce+4 and V+5 ions). Electrochemical polarization tests established that the Ti-Al-Zr alloy was in passive condition up to a potential of 4000 mVAg/AgCl even at 75 °C, and it showed uniform corrosion. SS304L, however, showed severe intergranular corrosion at a much lower anodic potential, thus establishing better corrosion resistance for Ti-Al-Zr alloy in the aggressive nitric acid environment.

Degradation kinetics of alkali-activated mortar in aggressive citric acid environment

Acid attack is a complex phenomenon arising in construction industries worldwide as it is responsible for the deterioration of concrete in acidic environments resulting in premature degradation with regard to mass changes, weakening of mechanical properties, and increase in porosity due to calcium leaching. This paper investigates the citric acid resistance of geopolymer composites (GP) and its comparison with conventional concrete system (OPC) in lower and higher concentrations of acid medium. The GP samples displayed increased resistance to citric acid attack than OPC system in terms of mass and strength loss. It was also found that geopolymer mortar made with a blend of ground granulated blast furnace slag (GGBS) and red mud (RM) offered increased acid resistance based on the parameters studied in the degradation kinetics

Development of zero cement composite for the protection of concrete sewage pipes from corrosion and fatbergs

The pursuit of environmental friendly alternatives for ordinary Portland cement (OPC) finds increased attention when the latter poses serious durability issues in major infrastructure applications, such as sewage drainage pipes. The presence of large quantities of free lime in OPC concrete used in the manufacturing of sewage pipes, exposes them to (i) concrete corrosion in acidic sewage environment, and (ii) clogging of sewage network due to the formation of calcified fatbergs. There appears to be very limited or no research on the development of an eco-friendly zero cement composite that can protect the concrete sewage pipes from corrosion and can eliminate the free lime that contributes towards the formation of fatbergs. Therefore, to address this research gap, an experimental investigation was undertaken on quaternary blended cement composites containing nano-silica, fly-ash, slag, and hydrated lime. These cement composites were tested for compressive strength to identify their mechanical properties, and an acid attack durability test exposed to 3.5% sulfuric acid solution to identify their corrosion performance in an aggressive acid environment. X-ray diffraction, thermogravimetric and scanning electron microscopic analysis were carried out to ascertain the physicochemical properties of the cement composites. The results show that an eco-friendly zero cement concrete developed with a quaternary blended mix of nano-silica, fly-ash, slag and hydrated lime successfully addresses the mechanical and durability requirements of the concrete sewage pipes. It surpasses ASTM's minimum strength requirement for the sewage pipes, and brings about a significant improvement in withstanding an aggressive acidic environment as evident from the 96% reduction in its mass loss due to concrete corrosion, compared to that of the OPC concrete. Moreover, the high amorphous silica content present in nano silica, slag and fly-ash assists in totally consuming the free lime that interacts with fat, oil and grease to produce fatbergs.

A critical review on the effect of organic acids on cement-based materials

Ingression of acids into concrete structure arrests its long-term durability by the progressive degradation of the highly alkaline cementitious materials. Acid attack results in the decalcification of hydration products leading to higher inherent porosity and both micro-macro cracks, providing a path for the passage of aggressive ions into the interior of concrete. Amplification of agriculture and food industries such as the breeding, dairy or sugar industries produce large quantities of effluents that are the major sources of organic acids. These effluents have complex acidic compositions leading to serious degradation of structures made for their production, collection, storage and treatment. New binder systems that are capable of proposing extensive long term durability in aggressive acidic environment and also being a sustainable option need to be evolved. From earlier studies, application of various binder systems containing materials such as fly ash, ground granulated blast furnace slag, silica fume, bagasse ash etc. has an influence on the hydration products, micro-structural and macro-structural changes in cement-based materials when subjected to aggressive acidic media, thus enhancing the performance and durability of concrete structures. This paper outlines the basic mechanism of organic acid attack and highlights the influence of various binder systems on the alteration of degradation kinetics when exposed to various organic acids.

A comprehensive study of mild steel corrosion in the aggressive acidic environment using CMPPC, a substituted pyrazole derivative

CMPPC, 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde was synthesised from 3-methyl-1-phenyl-5-pyrazolone, and its corrosion protection properties for mild steel in HCl were studied using mass loss studies, impedance spectroscopy, polarisation studies, adsorption studies and basic quantum chemical calculations. The protection efficiency decreases with an increase in temperature and acid concentration but increases with an increase in the concentration of the inhibitor. Electroanalytical screening reveals that the molecule behaves like a mixed-type inhibitor. CMPPC adsorbs on the metal surface, and the phenomenon obeys Langmuir adsorption isotherm pattern. Various kinetic and thermodynamic parameters are calculated using Arrhenius and Van’t Hoff approaches. Molecular dynamics simulations are employed using computational chemistry protocols. The results indicate that the CMPPC offers maximum interaction on Fe(111) plane of the metal surface.

INFLUENCE OF SULFURIC ACID ATTACK ON CONCRETE WITH INDUSTRIAL WASTE

The paper aims at investigating cement composites with incorporated wastes such as blast granulated slag, fly ash, or micro silica regarding their durability and resistivity against aggressive acidic environments. An aggressive acidic attack was simulated with H2SO4 with a pH of 1.95. The experiments proceeded under model laboratory conditions over a period of 6 weeks, and the accelerated tank leaching test was applied. Both physical (mass of samples, water absorption, and surface disruption) and chemical parameters of concretes (pH, leachability of main components, chemical composition) were examined. The changes in the mass of samples, surface changes, as well as absorbability increases were observed after exposure to sulfuric attack. The leached-out amounts of calcium, silicon, aluminum, and iron, measured using X-ray fluorescence analysis, varied depending on the composition of the analyzed composite and the kind of waste incorporated. The samples with micro silica and slag were identified to be the most durable, regarding the leaching of basic inorganic compounds of the cement matrix. The sample with fly ash was observed to have the lowest change in water absorbability. The positive effect of incorporating waste into cement composite was confirmed when compared to a concrete sample without any waste added.

Severe microbiologically influenced corrosion of S32654 super austenitic stainless steel by acid producing bacterium Acidithiobacillus caldus SM-1

Microbiologically influenced corrosion (MIC) of S32654 (654SMO) super austenitic stainless steel (SASS) by acid producing bacterium (APB), Acidithiobacillus caldus SM-1, a strain of sulfur-oxidizing bacteria (SOB) used in biohydrometallurgy field, was investigated using electrochemical measurements and surface characterizations during a 14-day immersion test. The results indicated that S32654 SASS was susceptible to MIC by APB, and A. caldus SM-1 was capable of producing an aggressive acidic environment underneath the biofilm, resulting in the dissolution of the passive film and severe pitting attacks against S32654 SASS, which is commonly regarded as a corrosion resistant material.

A study of deterioration of cement paste due to acid attack using X-ray computed micro-tomography

Cementitious materials are highly vulnerable to rapid and serious deterioration in aggressive acidic environments. The aim of this paper is to understand the microstructure deterioration of cement paste due to acid attack using the non-destructive technique called X-ray computed micro-tomography (micro-CT). To investigate this deterioration, an accelerated static immersion based leaching test with periodic abrasive action was performed on cement paste specimens of size 10 × 10 × 60 mm, prepared using ordinary Portland cement with a water-to-cement ratio of 0·40. After 28 d of initial curing in saturated lime water, specimens were exposed to 1% sulfuric, 1% hydrochloric, 0·5 M acetic and 0·5 M citric acid solutions for a maximum period of 6 weeks. X-ray micro-CT was used for imaging the deteriorated specimens to investigate the changes in microstructure. Various parameters related to degradation were also deduced based on the image analysis performed on the CT images in order to evaluate the performance of the cement paste in various acid solutions. Parameters such as altered depth/area could be considered as primary indicators of attack, which can be best captured and analysed using X-ray CT.

Electrical conducting Xanthan Gum-graft-polyaniline as corrosion inhibitor for aluminum in hydrochloric acid environment

The work reports the preparation and characterization of Polyaniline (PANI) grafted on Xanthan Gum (XG) backbone as a conducting biopolymer. The grafting has been achieved by polymerization of aniline under acidic conditions employing microwave radiation. The formation of the graft copolymer has been confirmed by FTIR, UV-Vis and TGA data. The DC conductivity measurements indicated enhancement in conductivity of XG on grafting with PANI. The corrosion inhibitor property of XG and XG-g-PANI in aggressive acid environment was checked on aluminum surface by weight loss, potentiodynamic polarization, AC impedance and surface studies. Both the samples are found to be potential inhibitors, the effect being significantly higher for the grafted sample.

Nature of tonsteins in the Azeisk deposit of the Irkutsk Coal Basin (Siberia, Russia)

In this paper data on the mineral and chemical composition of tonsteins from the Jurassic Azeisk deposit located in the Irkutsk Basin (South Siberia, Russia) are presented. The mineral composition includes kaolinite (87–89%); quartz (3.0–4.0%), cristobalite (4.9–5.3%), illite (1.9–2.1%) and feldspar (1.0–2.0%). Accessory minerals comprise zircon, monazite, uranium oxides, native minerals (gold, silver, nickel, zinc, tungsten, and silicon), sulfides and intermetallic compounds. The tonsteins and coals of the Azeisk deposit have high concentrations of REE, Y, Zr, Hf, U, Th, Ta, Sn, Ga, Cu, Pb, Se, Hg, Sb, and Te. The highest concentrations of these elements were found at the contact with coals. The enrichment of the coal with lithophile rare metals is possibly caused by their leaching from the tonsteins. The accumulation of these trace elements is a characteristic feature in coals both above and below the tonsteins. The width of the enrichment in the coal zone depends on the properties of chemical elements and features of the coal properties and character of interaction between the coals and tonsteins. The authors verify the pyroclastic nature of the initial matter of the tonsteins of the Azeisk deposit. Mineralogical and geochemical data from the tonsteins suggest a felsic (rhyolite) composition for the original volcanic matter that was altered in the aggressive acidic environments of the peat bogs. As a result of the burial of this material in a paleo-peatland some of the elements typical of felsic pyroclastics accumulated.

On exfoliation corrosion of alloy 2060 T8E30 in an aggressive acid environment

Abstract In this study, we investigated exfoliation corrosion (EFC) of the alloy 2060 T3E80 in an aggressive solution, namely EXCO. The pH value increased from 0.25 at the initial time point to 3.45 after 96 h of testing. In Stage 1 (0.25

Analysis of the Durability of Lightweight Concrete Protected by an Acrylic Layer in an Aggressive Acid Environment

When exposed to adverse conditions the concrete must be protected so as to maintain absorption at acceptable levels. This paper presents the assessment of a lightweight expanded clay concrete protected by an acrylic layer exposed to an aggressive environment. The specimens were prepared with 370kg/m3 of cement and the water-binder ratio of 0.50 corresponds to the value established in NBR 6118 types for concrete subjected to highly aggressive environments. The concrete produced presented specific mass of 1,600kg/m3, dry consistency and compressive strength of 25MPa. Visual inspection shows that the protected specimens of lightweight concrete presented a clear reduction of the loss of cohesion of the grout caused by the attack as well as lower water absorption and mass loss. The acrylic layer assessed as a surface protector presented a good adherence level to the substrate and efficiency since it reduced the penetration of the aggressive agent, thus minimizing degradation and increasing durability of the lightweight expanded clay concrete.

Degradation of Plastic Pipe Surfaces in Contact with an Aggressive Acidic Environment

Polyethylene (PE) pipes transporting water are vulnerable to aggressive agents which are able to diffuse through buried plastic pipes causing oxidative degradation. The latter may occur as a result of a spontaneous chemical reaction with atmospheric oxygen or as an induced oxidizing reaction with disinfectant agents (i.e. chlorine or hypochlorous acid ions) which are commonly added to municipal water supplies for public health reasons. Basically, PE pipes surfaces undergo undesired oxidation reactions whenever they are in contact with adverse external environments and/or when conveying fluids which tend to modify internal pipe wall structure. In this work, the effects of distilled water and diluted hydrochloric acid at different concentrations on the external and internal surfaces of a high density polyethylene (HDPE-100) pipe are studied. The measured parameters are roughness and hardness in order to appreciate surface quality variances in as-received and degraded materials. Initially the outer surface is rougher than the inner's one but in contact with distilled water, the external surface roughness increased by 6% although the internal face of the tube revealed a small decrease (<5%). When exposed to hydrochloric acid, pipe roughness (μm) showed a substantial increase as a function of increasing medium concentration. Crystallinity (χ in %) measurements confirmed the gap between outer (51.55%) and inner (61.31%) surfaces indicating that degradation has taken place at the structural level when HDPE was in contact with such aggressive agents. On the other hand, it is revealed that after exposure to oxidizing environments, crystallinity dropped by approximately one third when compared to as-received material; therefore reducing resistance to fracture and subsequently pipe lifetime.