Immersion Period Research Articles

The effect of CaCO3 deposit on corrosion of NaCl - Alkali/ surfactant/ polymer produced water pipeline

In this work, the corrosion behavior of the CaCO3 layer deposited on the NaCl-alkaline/surfactant/polymer flooding pipeline steel is studied. The results showed that in the non-galvanically-coupled state, localized corrosion occurred on the CaCO3 deposit electrode, and uniform corrosion occurred on the bare electrode. The corrosion of the carbon steel was inhibited by the deposited CaCO3 layer, and the galvanic corrosion occurred, which promoted the corrosion of the bare electrode and inhibited the corrosion of the CaCO3 deposit electrode. The polarity of the bare electrode and the CaCO3 deposit electrode was reversed after the 1 h immersion. During the immersion period below 1 h, the CaCO3 deposit electrode was the anode and the bare electrode was the cathode. However, after the immersion for 1 h, the bare electrode became the anode, and the CaCO3 deposit electrode became the cathode.

The In Vitro Impact of Two Scaffold-Type Structure Dental Ceramics on the Viability, Morphology, and Cellular Migration of Pharyngeal Cancer Cells

There is a growing trend with respect to the use of ceramic materials in dental practice. With an increase in the number of cases of head and neck cancer, the use of dental implants in these patients is subject to controversy. Consequently, the purpose of the present study was to evaluate the impact of two ceramic materials on the viability, proliferation, migration, and structure of the cytoskeleton and nuclei of pharyngeal cancer cells. Therefore, samples of the two ceramic were immersed in artificial saliva with three different pH values in order to better simulate the natural biological environment. A 21-day immersion period was followed by testing of the saliva on pharyngeal cancer cell line Detroit-562 for its viability, morphology, and migration, as well as its effects on the nucleus and cytoskeleton. The results of the study after stimulation of Detroit-562 cells for 72 h with the three types of artificial saliva in which the ceramic materials were immersed indicated the following: (i) viability of cells did not change significantly, with the percentage of viable cells not falling below 90%; (ii) no morphological changes were recorded, with the shape and number of cells being similar to that of the control cells; (iii) the scratch assay method indicated that the two types of ceramics do not stimulate cell migration; and (iv) fluorescence immunocytochemistry revealed that both the nucleus and the cytoskeleton distributions were unaltered, as they were observed in unstimulated cells. The preliminary results of the study indicate that the investigated ceramic materials did not interact unfavorably with tumor cells when immersed in artificial saliva, thereby supporting the possibility of their safe use in cancer patients.

Colour Stability of 3D-Printed and Prefabricated Denture Teeth after Immersion in Different Colouring Agents-An In Vitro Study.

This study investigated the colour stability of three dimensional (3D)-printed and conventional denture teeth after immersion in different colourants. A total of 60 artificial maxillary central incisors were selected from three types of materials: 3D-printed dental resin (NextDent, 3D Systems, Soesterberg, The Netherlands), prefabricated acrylic teeth in Ivostar Shade (Ivoclar Vivadent, Schaan, Liechtenstein), and SpofaDent Plus in shade A2 (SpofaDental, Jičín, Czechia). These were immersed in four types of colourants at room temperature (23 °C ± 1 °C), including artificial saliva (pH = 6.8) as a control group, coffee, red wine, and Coca-Cola (n = 5). The temperature and the pH of the colouring agents were maintained throughout all immersion periods. After 7 days (T1), 14 days (T2), and 21 days (T3), the ∆E values were measured with a SpectroShade Micro (SpectroShade, Oxnard, CA, USA) spectrophotometer. Their means were then calculated and compared by two-way ANOVA. The independent factors, immersion time and different staining solutions, as well as the interaction between these factors, significantly influenced ΔE. The highest and the lowest mean ∆Es were recorded for prefabricated teeth in red wine, and 3D-printed teeth in artificial saliva, respectively. All the specimens demonstrated an increased colour change at T1 compared to T3, and the difference in mean ∆E was statistically significant.

The acquisition of L2 Spanish intonation

Abstract This study examines the developmental patterns manifested in the intonational grammar of American English-speaking learners of Spanish based on their use of intonational features (e.g., [±delayed peak], [±deaccentuation], or [±compression]) involved in focus marking in three different discursive contexts (i.e., broad focus, informational subject focus and corrective subject focus). The data, collected through a Question & Answer pairs task performed by learners and native speakers, suggests that while development towards the target language is possible, it is constrained by markedness and learnability. The analysis of the results is framed within Mennen’s L2 Intonation Learning theory, which considers the multidimensionality that characterizes intonational grammars and the complexity of the acquisition process as a result of it. Individual factors related to the learners’ experience (i.e., experience abroad and hours of exposure) were examined and extended periods of immersion (i.e., more than 8 months) were found to have a positive effect.

Rivers as a potential dispersing agent of the invasive tree Acacia dealbata

BackgroundThe silver wattle Acacia dealbata is a fast-growing tree from Australia that has become naturalised in different regions of the world, attaining invasive status in most of them. In Chile, A. dealbata reaches large abundances along banks and floodplains of invaded fluvial systems, suggesting that rivers may act as a vector for seed dispersal. As hydrochory has not been documented previously in this species, the aim of this study is to evaluate the potential for water dispersal of seeds of this invasive tree along rivers.MethodsSeed samples from rivers were collected at three sites along two A. dealbata-invaded rivers within the Cachapoal basin, central Chile. Number of seeds collected was contrasted versus hydraulic and local conditions with RDA. Seed buoyancy and sedimentation velocity were determined and compared between sites with an ANCOVA. Finally, the probability of seed germination after long periods of immersion in water was assessed, simulating transport conditions in the flow. Germination results were tested with a GLM.ResultsResults indicate that increasing abundance of A. dealbata seeds in the flow is related to the level of turbulence of the flow. Seeds display high floatability but their sedimentation velocity is high when they do sink. Finally, silver wattle seeds can germinate after long periods (many weeks) of immersion in water; however, their probability of germination depends to a large extent on whether seeds are scarified or not.ConclusionsBased on the evidence collected, we suggest that the seeds of A. dealbata have the necessary traits to be dispersed by rivers, this being the first research testing this hypothesis. The success of hydrochory of A. dealbata would depend on river flow turbulence, and whether there are natural mechanisms for scarifying the seeds either before or during transport. The proposed methodology can be used to assess river hydrochory for any tree species.

Hierarchical Ti3C2T@MoS2 heterostructures: A first principles calculation and application in corrosion/wear protection

• The interface interactions between Ti 3 C 2 T x and MoS 2 were elaborately investigated using first-principles calculations based on DFT. • The van der waals forces play a crucial role in Ti 3 C 2 T x @MoS 2 heterostructures. • Ti 3 C 2 T x @MoS 2 heterostructure composites with 2D hierarchical structures were prepared via a facile one-step hydrothermal method. • The as-prepared epoxy composite coating showed enhanced anticorrosion and antiwear properties. Surface and interface engineering plays a crucial role in modulating the properties of materials, especially two-dimensional (2D) materials. Hence, a strategy, forming heterostructures with MoS 2 , is proposed to overcome the natural agglomeration of Ti 3 C 2 T x MXene nanosheets. Most importantly, the interactions between Ti 3 C 2 T x and MoS 2 were elaborately investigated by first-principles calculations based on density functional theory (DFT) for the first time. The calculations demonstrate that van der Waals forces dominate the interface interactions of Ti 3 C 2 T x and MoS 2 , rendering Ti 3 C 2 T x @MoS 2 heterostructures favorable stability. The Ti 3 C 2 T x @MoS 2 heterostructure composites were synthesized through a facile one-step hydrothermal method and exhibit a 2D hierarchical structure. Furthermore, the corrosion and tribological properties of epoxy composite coatings with varying proportions of Ti 3 C 2 T x @MoS 2 composites were studied in detail. As a result, the epoxy composite coating with 0.1 wt.% Ti 3 C 2 T x @MoS 2 composites (Ti 3 C 2 T x @MoS 2 -0.1) exhibits excellent corrosion protection and antiwear performances. The Ti 3 C 2 T x @MoS 2 -0.1 keeps the largest low-frequency impedance modulus (| Z | 0. 01 Hz) and coating resistance ( R c ) during the whole immersion period. Its wear rate is 0.09 μm 3 /(N μm) under the load of 10 N, one half of that of pure epoxy coating (EP). This work further broadens the application of MXene-based heterostructure composites.

Celery Root Phenols Content, Antioxidant Capacities and Their Correlations after Osmotic Dehydration in Molasses.

The osmotic dehydration (OD) of celery root in sugar beet molasses was studied at three temperatures (20, 35, and 50 °C) and three immersion periods (1, 3, and 5 h) in order to examine the changes in antioxidant potential and phenolic profile of celery root throughout the process. The antioxidant capacity (AOC) of dehydrated samples was evaluated by spectrophotometric and polarographic assays, the total phenolic content by the Folin-Ciocalteu method, and the individual phenolic compounds by HPLC-DAD. As a result of OD in molasses, the AOC and phenols content in samples increased proportionally to the augmentation of temperature and the immersion time. Vanillic acid, syringic acid, and catechin were detected in dehydrated samples as a result of transfer from molasses. Compared to fresh celery root, the content of identified phenols in osmodehydrated samples was improved from 1.5 to 6.2 times. Strong correlations between applied assays were obtained, except for the DPPH. Based on the correlation analysis chlorogenic acid, gallic acid, chrysin, catechin, and kaempferol showed the greatest contribution to the overall AOC of osmodehydrated celery root. Molasses, an agro-industrial waste from sugar production, could be valorized as a valuable osmotic solution.

IMPACT ASSESSMENT OF MUNICIPAL CORPORATION CAMPAIGNING ON PUBLIC AWARENESS TO CONSERVE THE TAPI RIVER WITH REFERENCE TO IDOL IMMERSION: A STATISTICAL EVALUATION

India is the culturally diversified country where large numbers of festivals are celebrated everyyear. Among these festivals, Ganesh Chaturthi is one of the important festivals and during this festivaldifferent sized Ganesh idols are worshiped for few days and later on immersed in nearby water body. Theidol immersion process is the major cause of water quality deterioration and ultimate increase the pollutionin water resources. The present study focused on evaluation of the municipal corporation campaigning andpublic awareness to conserve the Tapi river which gets polluted due to idol immersion. To fulfill the objectiveof the present study, water samples were collected during the Ganesh festivals of 2010, 2014 & 2019 andwere analyzed for important water quality parameters including temperature, pH, dissolved oxygen, totalhardness, total alkalinity, bio-chemical oxygen demand, chemical oxygen demand, oil & grease and totalcalcium. Results showed that the water quality parameters were more fluctuated during the idol immersionof 2010 and 2014 compared to 2019. These results were statistically verified and observed that temperatureand BOD had significant changes in the year 2014 whereas total alkalinity, COD and oil & grease exhibitedsignificant changes during the year 2010 and 2014. Insignificant changes in temperature, BOD, totalhardness and significant changes in COD were noted during immersion and post immersion period of 2019.The outcome of present study clearly indicated that campaigning of municipal corporation is effectivelywork to aware the public to use of ecofriendly idols, idol immersion in artificial small water holdings etc.to conserve the Tapi River during the idol immersion.

Xylopia aethiopica EXTRACT AS GREEN AND ECO-FRIENDLY CORROSION INHIBITOR AND ITS QUANTUM CHEMICAL ANALYSIS.

This work examines the corrosion inhibitory behavior of Xylopia aethiopica stem bark and root bark extracts respectively on corrosion of mild steel in 2M HCl solution and their quantum chemical analysis using gravimetric technique and quantum computational modeling. The corrosion rates of the mild steel coupons in blank HCl solutions were found to increase with increase in concentration of the corrodent, period of immersion and rise in temperature. On the other hand, the corrosion rate decreased in the acid solution containing the test extracts and the decrease became more pronounced on increase in the concentrations of Xylopia aethiopica stem bark and root bark extracts respectively. The decrease in corrosion rate indicates that the extracts inhibited corrosion of mild steel in the acid solution and inhibition efficiency increased with increase in extract concentrations. The inhibition is attributed to adsorption of the test extract constituent molecules on the mild steel surface, forming a film layer that protects the metal surface from the corrodent. Results of quantum chemical computational analysis proved that, 3-dimethyl- 1-vinylcyclohexene among the constituent compounds of Xylopia aethiopica bark extract would be the most likely organic compound to share electrons with the metal surface for possible adsorption bond. The adsorption of the extract molecules on the mild steel surface fitted into Langmuir adsorption isotherm with slope values of 0.86 and 0.98 for Xylopia aethiopica root bark and stem bark extracts respectively, and regression correlation (R2) values of 1.0 and 0.99 for root and stem extracts respectively.

Assessing writing development during study abroad

Abstract In research about second language (L2) development during study abroad (SA), writing is underrepresented. This is partly due to the difficulty of designing adequate tasks and measures to gauge writing development during a short immersion period. Our study explores the applicability of a narrative task assessed in terms of both linguistic complexity, accuracy, and fluency (CAF) and functional adequacy (FA), a novelty in SA writing research. Texts written by 30 advanced students of L2 German before and after SA were analysed. The results show moderate correlations between the measures for fluency and lexical variation and two FA dimensions. This suggests that, in the SA context, CAF and FA develop together to a certain extent, although the constructs are conceptually different.

Designing a corrosion resistance system using modified graphene oxide-epoxy microcapsules for enhancing the adhesion strength of the epoxy coatings

New microencapsulated material with advanced corrosion resistance activity and superior adhesion strength on the steel sample was synthesized by in-situ polymerization. In this process, urea-formaldehyde was used as capsule shell material for encapsulating modified graphene oxide. The formation of microcapsules was effectively evidenced by FT-IR, SEM, and TGA-DSC analyses. Initially, graphene oxide was modified by the adsorption of Catharanthus roseus L. (C.R) leaves extract and characterized by FT-IR, SEM, EDX, and DFT studies. GO-C.R and UF-GO-C.R (microcapsules) were separately impregnated into epoxy resin and fabricated on the steel substrates. The anti-corrosion performance of UF-GO-C.R/Epoxy in comparison with neat GO-C.R/Epoxy coated sample was evaluated by electrochemical impedance spectroscopy (EIS) and salt spray test. Results reveal that UF-GO-C.R microcapsules in epoxy matrix showed the protection efficiency of 83.6 % after the immersion period of 7 days in 3.5 % NaCl solution which was relatively higher than those with neat GO-C.R. In addition, the coating loaded with UF-GO-C.R microcapsules showed improvement in the adhesion of epoxy coatings on the steel surface which was evident from the increase in peel strength (290 N) through peel-off adhesion test.

Cynodon dactylon L. extract as an eco-friendly corrosion inhibitor of mild steel in saline solution

Corrosion-induced loss of metal integrity is a serious industrial concern. One of the most reliable and cost-effective corrosion reduction solutions is corrosion inhibitor innovation. The aim of this investigation therefore, is to study the corrosion inhibition of Cynodon dactylon L (Bermuda grass) extract on mild steel in a 3.5% NaCl solution. The plant was extracted with 80% ethanol and different concentrations were tested at a temperature range of 30 to 60OC and for various immersion time ranging from 4 to 72 hours using gravimetric (Weight Loss) method. The results showed that Cynodon dactylon extract exhibited strong corrosion inhibition efficiency (97.78%.). The inhibition efficiency of the Cynodon dactylon extract increased with an increase of extract concentration and through the immersion periods but decreased with an increase of the temperature. The inhibitive effect could be attributed to the presence of some phytochemical compounds in the plant which were adsorbed on the surface of the mild steel.

Influence of partial substitution of Ti for Al on microstructure, thermal stability and corrosion resistance of novel quaternary Ni33.3Y33.3Al33.4-xTix medium entropy metallic glasses

In this present study, the influence of partial substitution of Ti for Al on microstructure, thermal stability and corrosion resistance of novel quaternary low-density Ni33.3Y33.3Al33.4-xTix (x = 3∼21 at.%) medium entropy metallic glass ribbons (ME-MG ribbons) was investigated. According to the rule of atomic radius similarity, by gradually replacing Al by Ti, we have synthesized a series of multi-component glassy alloy ribbons via using a single roller melt-spinning technique and also have examined their phase structure, thermal characteristics, microhardness and anti-corrosion properties. Besides, the phase composition of some representative annealed ribbon samples and the crystallization activation energy of these melt-spun ME-MG ribbons have been also determined and studied in detail. Results show that all of the rapidly solidified alloy ribbons can maintain completely amorphous nature. However, the thermal stability of ME-MG ribbons becomes reduced with the increasing Ti content. The maximum crystallization onset temperature at the heating rate of 20 K/min is around 706.65 K for Ni33.3Y33.3Al30.4Ti3 alloy ribbons. The maximum apparent activation energy of crystallization by means of thermodynamic analysis can be up to ∼803 kJ/mol for Ni33.3Y33.3Al21.4Ti12 alloy ribbons. The average microhardness value of these metallic ribbons can reach 455 HV0.1 or more when Ti content is less than 15 at.%, which is approximately 1.5 times the hardness of the Al-based amorphous alloy ribbons. The microstructural characterization of each ME-MG ribbon surface in as-received state and after a period of 45-hour and 75-hour corrosion immersion in 0.6 M NaCl solution was applied by scanning electron microscopy as well. Substituting moderately Al with Ti can effectively improve the anti-corrosion ability; the most positive pitting corrosion potential and the smallest corrosion current density are approximately -0.145 VSCE and 0.045 μA/cm2 for Ni33.3Y33.3Al24.4Ti9 and Ni33.3Y33.3Al27.4Ti6 ME-MG ribbons, respectively. Thus, it can be deduced that these new-fashioned ME-MG ribbons possess the superior anti-corrosion property, higher microhardness and acceptable thermal stability simultaneously, which may open momentous possibilities for the development and practical application of high-performance metal materials.

Corrosion Behavior and Microstructure of Cu-Based Composite Coatings Deposited by Cold Spraying

This study aimed to prepare Cu-based coatings with excellent corrosion resistance by cold spraying. Cu, Zn, and Al particles with different mass ratios were mechanically blended as the feedstock materials. The microstructure, element content, mechanical properties, and corrosion resistance of the coatings were investigated. Results showed that all the prepared coatings presented a dense microstructure. In addition, the thickness of the coatings exceeded 290 μm, and the existence of the “hammer effect” made the thickness and hardness of the coatings present an obvious negative correlation. Electrochemical test results indicated that changes in the element content could significantly affect the corrosion behavior of coatings. During the immersion period, the coatings containing Al exhibited better corrosion resistance.

Strength and Durability Parameters of Brick Aggregate Concrete Incorporating Rice Husk Ash as a Partial Replacement of Cement

This study assessed the strength and durability parameters of brick aggregate concrete (BAC) incorporating rice husk ash (RHA) as a partial replacement of cement. For this, concrete cylinders (100 mm × 200 mm) were made with 0% (control) to 25% RHA as a partial replacement of ordinary Portland cement (OPC) at a mix proportion of 1 : 1.5 : 3 and a water-to-binder (w/b) ratio of 0.50. Specimens were immersed separately in normal water, 3% sodium chloride (NaCl), 5% sodium sulfate (Na2SO4), 5% magnesium sulfate (MgSO4), 1% hydrochloric acid (HCl), and 1% sulfuric acid (H2SO4) solutions for several immersion periods. The slump test results indicated that the workability of BAC containing RHA (RBAC) decreased about 29.69%–75.02% compared to control (0% RHA). After 90 days, the BAC containing RHA (up to 15% replacement) was found approximately 2.28%–6.64% greater compressive strength than that of control concrete. In addition, water absorption and porosity of RBAC were around 17.59%–40.73% and 12.12%–35.68% lower than that of control concrete, respectively. Similarly, RBAC (up to 25% replacement) exhibited roughly 35.62%–54.79% higher resistance against chloride attack and 0.39%–4.56% better resistance against Na2SO4 attack (up to 15% replacement), however, it exhibited inferior resistance against MgSO4 attack compared to control. Meanwhile, BAC with 10% RHA showed about 5.35% and 1.00% superior performance than that of control concrete against HCl and H2SO4 attack, respectively. The relationships between the strength and durability parameters of RBAC also suggested that RHA contributes to improving the strength and durability parameters of BAC.

Physical and Mechanical Properties and Decay Resistance of Poplar Modified with mDMDHEU

Chemical modification as a non-biocidal treatment is an effective method to improve physical and biological properties of wood. Poplar is a fast growing species but has poor dimensional stability and durability in addition to low mechanical properties. Low molecular weight Dimethylol dihydroxyethyleneurea (mDMDHEU) was used to improve the properties of poplar mainly dimensional stability and decay resistance. Results indicated high anti-swelling efficiency (ASE), but low variation between both concentrations of mDMDHEU. Tangential swelling was greatly reduced by mDMDHEU treatment during the water immersion period. Untreated poplar samples were severely decayed as compared to modified samples. Modified samples showed lower bending strength unlike to compression strength. Ester peak at 1720 cm-1 revealed chemical reaction between chemical reagent and wood cell wall components. Control samples exhibited considerably higher thermal degradation when compared to the samples modified with mDMDHEU.

Corrosion mechanisms of AZ31 magnesium alloy: Importance of starting pH and its evolution

AbstractThis article aims at improving the understanding of the corrosion mechanism of AZ31 magnesium alloys during a long period of immersion in an aqueous electrolyte. In particular, the influence of the starting pH of the electrolyte on the oxidation of AZ31 alloy and its evolution due to corrosion phenomena were investigated. Several electrolytes with different pH values containing or not chlorides were used. The electrochemical properties of the metal substrate in these electrolytes were studied as a function of immersion time by electrochemical impedance spectroscopy. The kinetics of the reactions were determined by potentiodynamic polarization as well as dihydrogen evolution measurements by eudiometry. All these tests were carried out while the sample surface and electrolyte volume remained constant. The corrosion products generated on the alloy surface were analyzed by X‐ray photoelectrons spectrometry. This study has shown that the evolution of the corrosion rate and the corrosion products depends greatly on the initial pH and the nature of the used electrolyte. Alkaline electrolyte leads to a passive protective layer that can be locally destroyed by chloride ions. For a neutral chloride electrolyte, the strong increase of the pH due to the magnesium corrosion is not able to form a protective layer by precipitation of corrosion products. The kinetic and the corrosion extent are affected by the pH changes.

Influence of hot water blanching and saline immersion period on the thermal effusivity and the drying kinetics of hybrid solar drying of sweet potato chips

The purpose of this study was to investigate the effect of adding pre-treatment to solar dried sweet potato chips. The tested pre-treatments were blanching using hot water and saline immersion. Indeed, the potato chips were dried using a convective indirect solar dryer, equipped with a wind generator and glycerine as thermal storage. The system was built locally at the University of Agriculture in Umuahia, Abia State, Nigeria. The obtained experimental drying curves and kinetics were directly affected by the weather conditions, as the drying rate increased with the increase of the radiation and the ambient temperature and decreased with their decrease. Drying of the various pre-treated potato slices took 8–14 h to attain equilibrium moisture level under the variable external drying conditions. The drying curves were fitted to semi-empirical models. The results showed that the two-term exponential model was the best model that fitted the experimental data. Shrinkage was a vital phenomenon observed during the drying process, as the volume of the chips was reduced by 50%. The volume of samples treated by saline immersion was higher by 6% than non-treated samples. Shrinkage phenomenon was then introduced to determine the thermos-physical properties of sweet potato chips, with particular attention to the particle density, the bulk density, shape analysis, specific heat capacity, thermal diffusivity, and thermal effusivity. The particle and bulk density peaked at 1.41–1.44 g/cm3, and 1.52–1.53 g/cm3 respectively for all treatments. The thermal effusivity ranged from 17.6 to 7.93 W.S1/2.m−2.K−1 while the specific heat capacity ranged from 1028 to 2288 J/kg °C. All the thermo-physical properties were presented as a function of the volume or moisture content variation with a high degree of association. The results demonstrated the importance of shrinkage and its direct effect on the determination of the thermos-physical properties of the studied product for both pre-treated and untreated samples.

Pre-treatments in silicate solutions to mitigate reinforcing steel corrosion in chloride-contaminated environments

ABSTRACT Silicate ions were incorporated into a pre-treatment to mitigate corrosion in reinforcing steel bars. The efficiency of these pre-treatments was compared by testing steel samples in concrete pore simulating solutions contaminated with chloride ions. The study involved cyclic voltammetry, anodic polarisation curves and weight-loss tests following a 60-day immersion period. Surface analysis included micro-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The electrical properties of the film were analyzed by impedance spectroscopy and Mott–Schottky plots. Polarisation curves show higher pitting potentials and lower corrosion current densities when pre-treating with silicate ions. Localised attack appears after 60 days of immersion in solutions containing chloride ions, but weight loss is reduced by 75% for coupons pre-treated in silicate solutions. XPS and Raman spectra indicate that the presence of silicate ions affects the composition of the passive film and the corrosion products. The results show that pre-treatments in silicate solutions are effective to minimise steel corrosion in aggressive environments.

ADSORPTION AND ANTICORROSION PROPERTIES OF MILD-STEEL TREATED 2-[(3-HYDROXYLPYRIDIN-2-YL) AMINO]NAPHTHALENE-1,4-DIONE SCHIFF BASE IN 1M-HCL SOLUTION: SYNTHESIS, EXPERIMENTAL AND COMPUTATIONAL STUDIES

The title Schiff base LH obtained by the reflux condensation of 2-hydroxy-1,4-napthoquinone and 2-amino-3-hydroxypyridine has been characterized via conventional procedures. Adsorption and corrosion inhibition potentials of LH were examined by considering its inhibitory efficiency on mild steel in 1M HCl via weight loss assessment, scanning electron microscopy and density functional theory. Analytical and spectroscopic methods corroborate the bidendate ketoimine-tautomeric assemblage of LH and its stability at ambient temperature. The weight loss measurement was performed at mixt temperatures of 303-343 K and inhibitor concentrations of 1x10-5 M- 9x10-5 M with immersion period of 5 h. Higher efficiency of 94.6% was attained with an inhibitor concentration of 9x10-5 M at 303 K. The adsorption of LH on mild steel (ms) was found to conform with Langmuir absorption isotherm model, while free energy of adsorption showed a spontaneous physiosorption. The computed activation energy (Ea) along other thermodynamic parameters (ΔS and ΔH) was consistent with the latter. The SEM results revealed that the ms superficial was smooth with the inhibitor compared to the ms superficial without the inhibitor indicating inhibition of corrosion of the ms by establishing a layer of protection on the surface. The density functional theory result was in agreement with experimental results.