Ammonium Chloride Solution Research Articles

REDUCTION OF CONCENTRATE EFFLUENTS OF REVERSE OSMOSIS UNITS USED FOR TREATMENT OF WASTE WATER CONTAINING ORGANIC POLLUTION

Background Units for electrical desalination of oil, other chemical industries, as well as landfills for the storage of municipal solid waste (MSW) are sources of groundwater and surface water pollution with toxic decomposition products of organic substances. The ability to purify MSW filtrate to the level of modern requirements for purified water supplied to fishery reservoirs is a complex technical problem. The most effective technology for purifying solid waste filtrates is currently recognized as reverse osmosis technology, which allows to effectively remove from water not only contaminants in the ionic form (ammonium), but also dissolved organic compounds determined by the indicator of chemical oxygen consumption. A serious problem when using reverse osmosis technology is the formation of concentrates and their disposal. The consumption of concentrates in the treatment of leachate from MSW landfills by the reverse osmosis method is from 20 % to 30 % of all incoming water for treatment. Aims and Objectives The purpose of this work is to study the issues of processing mineralized wastewater containing oil products and other organic pollution (wastewater from electrical desalting plants, leachate from solid municipal waste storage sites) using reverse osmosis and nanofiltration methods. Results It is noted that a serious environmental problem is posed by reverse osmosis concentrates, which have a high content of salts and organic substances and are difficult to dispose of. It is proposed to use the separation of concentrates into solutions containing their components, depending on the value of the value of their retention using nanofiltration membranes. So, concentrates of reverse osmosis plants can be divided into solutions with a high content of organic substances and saline solutions (containing ammonium salts), the volumes of which are 10-20 times lower than the volumes of concentrates. Using the example of concentrates from reverse osmosis plants, it is shown how multicomponent solutions can be divided into highly concentrated solutions of organic substances and saline solutions of ammonium chloride in order to simplify their further disposal. The technology of separation of solutions is described, using dilution of the concentrate with deionized water, which makes it possible to achieve separation of solutions into components depending on their selectivity - the degree of their retention by nanofiltration membranes.

Preparation of Slow-Release Insecticides from Biogas Slurry: Effectiveness of Ion Exchange Resin in the Adsorption and Release of Ammonia Nitrogen

The insecticidal ingredient in a biogas solution being fully utilized by cation exchange resin to produce slow-release insecticide is of great social value. In this work, the feasibility of ammonia nitrogen in a biogas slurry loaded on resin as a slow-release insecticide was evaluated by studying the effect of adsorption and the slow release of ammonia nitrogen by resin. The effects of the ammonia nitrogen concentration, resin dosage, adsorption time and pH value on the ammonia nitrogen adsorption by the resin were studied. The results showed that the ion exchange resin had a good adsorption effect on the ammonia nitrogen. With the increase of the resin dosage, time and ammonia nitrogen concentration, the adsorption capacity increased at first and then stabilized. The ammonia nitrogen adsorption capacity reached its maximum value (1.13 mg) when the pH value was 7. The adsorption process can be fitted well by the Langmuir isothermal adsorption equation and quasi-second-order kinetic model. Additionally, the release rate of the ammonia nitrogen increased with the increasing sodium chloride concentration. The adsorption capacity of ammonia nitrogen by the D113 (resin type) resin decreased by 15.8% compared with the ammonium chloride solution. The report shows that the ion exchange resin has a good adsorption effect on ammonia nitrogen, which is of guiding significance for expanding the raw materials for slow-release insecticides, improving the utilization rate of biogas slurry and cleaner production of slow-release insecticides from biogas slurry. Additionally, all variables showed statistical differences (p < 0.05).

Chalcopyrite leaching in ammonium chloride solutions under ambient conditions: Insight into the dissolution mechanism by XANES, Raman spectroscopy and electrochemical studies

Ammoniacal leaching solutions have been considered as an effective lixiviant for the oxidative dissolution of chalcopyrite. However, compared with the extensive studies of acidic chalcopyrite dissolution, the dissolution mechanism of chalcopyrite in ammoniacal solutions needs further understanding. In this study, the oxidative dissolution of chalcopyrite in ammonium chloride solutions under room temperature and pH 8.5 was studied by X-ray absorption near-edge spectroscopy (XANES), Raman spectroscopy and electrochemical impedance spectroscopy (EIS). Both batch leaching experiments and electrochemical studies showed that Cu(II) ions were more efficient than dissolved oxygen for chalcopyrite oxidation in ammonium chloride solutions. Leaching kinetics analysis showed that without the initial addition of Cu(II), chalcopyrite dissolution rate was controlled by two different stoichiometric chemical reactions: the initial and slow leaching stage controlled by dissolved oxygen; then predominated by Cu(II) rather than dissolved oxygen with a fast leaching rate when copper concentration exceeded a certain level (>0.12 g/L). Thiosulfate (S2O32−) rather than sulfate (SO42−) was confirmed as the primary soluble sulfur species produced during chalcopyrite dissolution. Decomposition of S2O32− in the presence of both O2 and Cu(II) resulted in the final stable product SO42− accompanied by the formation of other sulfur intermediate species, including S4O62− and SO32−. No evidence was found for the formation of elemental sulfur. Amorphous hematite (Fe2O3) and six-line ferrihydrite (5Fe2O3·9H2O) were the major components residing on the chalcopyrite surface, which were responsible for the slow dissolution rate at late stage. According to the present work, a model for the chalcopyrite dissolution mechanism in alkaline ammonium chloride solutions under ambient conditions is provided.

(Invited) Electroless Rhodium Deposition for Metallization of Advanced Interconnects

Over the past decades, the semiconductor industry managed to continuously increase performance at an impressive, steady rate by scaling all parts of the integrated devices to nanometer-size dimensions, thereby enormously increasing the number of transistors on the chip as well as decreasing the dimensions of the metallization [1]. Presently, Cu constitutes the largest material fraction as conductor in damascene trenches which can be deposited by electrochemical deposition (ECD) or electroless deposition (ELD) [2 – 6]. For next-generation interconnects, the material properties (electromigration) of Cu render it unreliable for producing ever more performant chips. Additionally, the necessity of a diffusion barrier layer for Cu strongly increases line resistance and negatively impacts device performance upon further down-scaling. Recently, various alternative metals, such as ruthenium, rhodium, and molybdenum, have been studied and start to be implemented to tackle performance losses due to the small dimensions of the metal structures [7 – 9]. Consequently, both wet-chemical deposition as well as controlled etching of these metals has become of interest [10 – 12].In our contribution, we present results of the development of an electroless deposition bath for rhodium, using ruthenium (II) hexammine as reducing agent. An electrochemical characterization of the anodic and cathodic reactions involved was performed in hydrochloric acid and ammonium chloride solutions. The stability of Rh3+ and [Ru(NH3)6]2+ was monitored using UV-vis spectroscopy. It was found that under oxygen-free conditions the hexammine complex can be kept stable in the ammonium-containing solution.Initially, deposition experiments were performed on PVD-Pt blanket thin films, for which a non-uniform coverage was observed. Therefore, to enhance the nucleation of the ELD process, we first deposited a thin Rh layer by electrochemical deposition, after which Rh was deposited using our ELD bath. Transmission electron microscopy and elemental mapping was used to characterize the morphology and chemical composition, respectively. Upon thermal treatment (forming gas, 420 °C, 20 min) crystal grain growth was observed. Acknowledgements The authors would like to thank the partners of IMEC's Industrial Affiliation Program (IIAP) on Advanced Interconnects.

The electrochemistry of ammonium dihydrogen phosphate, disodium phosphate, ammonium chloride on Mg‐based and polycrystalline Pt electrodes

AbstractIn this study, the electrochemical mechanisms of struvite formation were investigated by studying the behavior of Mg‐based and (poly)crystalline‐Pt electrodes in the presence of ammonium dihydrogen phosphate, disodium phosphate, and ammonium chloride solutions. It was found that a precipitate was formed on the Mg‐based electrodes, while the poly‐Pt electrode showed typical voltammetric features in aqueous electrolytes. The structure, morphology, and composition of the electrochemically obtained precipitates collected from the surface of the Mg‐based electrodes were analyzed by scanning electron microscopy (SEM), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). The results showed that the precipitate morphology was impacted by the composition of the electrolytes and the purity of the magnesium. Moreover, the Tafel kinetics and corrosion rates (vcorr) directly correlated with the electrolyte and the electrode material compositions, whereby both showed a general increase when the Mg‐based electrodes were employed in the presence of chloride anions. The Tafel slopes (β) obtained for the oxygen reduction reaction (ORR) with the poly‐Pt electrode showed a significant difference between the forward and reverse potential scans in the various electrolytes used, a finding which was mainly attributed to the adsorption of hydroxide species, alkali cations, and phosphate anions to the surface whereby these species blocked the ORR active sites.

SPECTROPHOTOMETRIC METHOD FOR DETERMINING GLYCOGEN CONCENTRATION IN HELMINTHS: INFLUENCE OF AMMONIUM CHLORIDE IN DIFFERENT TEMPERATURE RANGE

Spectrophotometric methods for determining glycogen content are used in studies to quantify the effect of anthelmintics on carbohydrate and energy metabolism of helminths. The most specific of them include the method proposed by Krisman C.R., which was later adapted by Danchenko E.O. and Chirkin A.A. to apply in forensic medicine, and Andreyanov O.N. et al. in helminthology. Saturated solutions of calcium chloride and ammonium chloride are used in the procedure. It is known that the solubility of salts depends on temperature. Krisman C.R. studied the effect of calcium chloride on the optical density of the analyzed solutions depending on temperatures, but no detailed studies were made on the role of ammonium chloride. The present paper presents data on the effect of ammonium chloride on the optical density of the analyzed samples under the influence of temperatures in the range of 10–30 oC. This salt introduced to neutralize alkali increases the optical density of the solutions. It is found that ammonium chloride not only neutralizes the decrease in optical density, but also causes its increase as temperatures increase. In salt-free samples, the deviation from the specified glycogen content (0.1 mg) in the range of 10 oC was 12.1%, and with the addition of ammonium chloride, it decreased and varied within 4–8.5%. To improve the accuracy of the analysis, it is recommended to avoid studies in large temperature ranges.

Potassium Available to Corn Plants Extracted by Ammonium Acetate, Ammonium Chloride, Mehlich-1 and Mehlich-3 Solutions in Southern Brazilian Soils

ABSTRACT The main Brazilian soil testing laboratories use Mehlich-1 solution for the determination of available potassium in the soil. However, this procedure has chemical and operational limitations. In search of alternatives for Mehlich-1, this study was to compare different extraction solutions, vis: Mehlich-1 and 3, and 1.0 mol L−1 ammonium chloride (NH4Cl) and 1.0 mol L−1 ammonium acetate (NH4OAc), as soil-K index to predict K availability to corn plants in southern Brazilian soils. The greenhouse pot experiment consisted of 30 soils grown with 2 corn crops. All soil-K index presented high correlation and determination coefficients between K uptake by corn plants and the K extracted from the soil. The Mehlich-1 solution was consistently better correlated with K uptake by corn plants than NH4OAc and NH4Cl but extracted less exchangeable K of the soils. Grouping soils with similar mineralogy and physicochemical properties enhances and improves the prediction of K availability for corn plants. Moreover, the K saturation index can be used as a sole indicator of K availability to plants. Overall, the results indicate that it is feasible to replace the traditional solution Mehlich-1 in the extraction of soil exchangeable K by solution of NH4Cl mol L−1 in laboratories that have an Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES).

Improvement of Membrane Distillation Using PVDF Membrane Incorporated with TiO2 Modified by Silane and Optimization of Fabricating Conditions

The objectives in this study are to improve the performance of PVDF membrane by incorporating TiO2 and silane at various dosages and optimize fabricating conditions by using response surface methodology (RSM) for membrane distillation (MD) application. The PVDF membrane was synthesized by phase inversion method using various TiO2, silane and polymer concentrations. Membranes were characterized by performing contact angle measurements, SEM and FTIR observations. Ammonia rejection and permeate flux were measured by operating a direct contact distillation module treating ammonium chloride solution. A PVDF membrane created by adding TiO2 modified by silane improved membrane hydrophobicity. However, the effect of silane on membrane hydrophobicity was less pronounced at higher TiO2 concentrations. Highest ammonium rejection was associated with the highest membrane hydrophobicity. RSM analysis showed that fabricating conditions to achieve highest flux (10.10 L/m2·h) and ammonium rejection (100.0%) could be obtained at 31.3% silane, 2.50% TiO2, and 15.48% polymer concentrations. With a PVDF-TiO2 composite membrane for MD application, the effect of TiO2 was dependent upon silane concentration. Increasing silane concentration improved membrane hydrophobicity and ammonium rejection. RSM analysis was found to bea useful way to explore optimum fabricating conditions of membranes for the permeate flux and ammonium rejection in MD.

ELECTROLYSIS TREATMENT OF AMMONIUM CHLORIDE WASTEWATER BY DOUBLE CHAMBER MEMBRANE PROCESS

Aiming at the problem that ammonium chloride wastewater generated from the rare earth and fertilizer industries is difficult to treat, combining with the actual case of a factory in Guangdong province that produced a large amount of ammonium chloride waste solution in the treatment of alkaline copper chloride etching liquid, this paper put forward the method of electrolysis to treat ammonium chloride wastewater and probed into the optimal experimental conditions. It was found that the anion exchange membrane was used to separate the electrolytic cell into a bipolar chamber, which could prevent the contact between chlorine gas and ammonium ion from producing explosive nitrogen trichloride, ensure the safety of operation, and effectively separate chlorine gas from the anode and hydrogen from the cathode, so as to facilitate products collection. On this basis, through exploring the impact of anode chamber and electrolyte concentration, cathode chamber ammonium chloride solution concentration, electrolytic time on treatment effect, optimized experimental condition was as follows:20 mL 5 g/L sodium chloride solution in the anode chamber, 20 mL 100 g/L of ammonium chloride solution in the cathode chamber, constant current of 0.3 A, and electrolysis time of 3 hours, then 93% of chloride ions were transformed into chlorine and sodium hypochlorite. Under this condition, the factory could make an income of at least RMB 1950 by treating 15 t of ammonium chloride waste liquid per day. The membrane electrolysis method could effectively remove chloride ions from ammonium chloride wastewater and produce chlorine gas, sodium hypochlorite and ammonia water. Compared with the traditional electrochemical treatment technology, it had the advantages of simple device and high removal rate, with controllable reaction rate.

Using solid carriers impregnated with ammonium ionic liquids for platinum(IV) recovery from chloride solutions

Platinum(IV) was extracted from chloride solution using kerosene solution of trioctyl ammonium chloride, methyltrioctylammonium chloride, and tetraoctyl ammonium chloride ionic liquids as solvents in high yields. To increase the Pt(IV) recovery and heterogenize the process for easy handling at industrial scale, these three ionic liquids were directly impregnated on some solid carriers, such as silica gel-60, silica gel-100, Amberlite XAD-7 ion-exchange resin, and Amberlite XAD-7 ion-exchange resin to form sorbents in nature of supported ionic liquid phase. The influence of some factors, such as ionic liquid and solid carrier structure, IL/Pt molar ratio, and ionic liquid loading as well as sorption isotherms, was investigated. The stripping and desorption of Pt(IV) using different eluents and reusability of ionic liquids and supported ionic liquid phases were also evaluated.

The effect of plasma electrolytic polishing on the surface properties of nitrocarburised steel

The effect of anodic plasma electrolytic polishing on the characteristics of low carbon steel (0.2 % C) after nitrocarburising was investigated. The formation of the modified layer including a hardened diffusion layer and a surface oxide layer occurs as a result of anodic plasma electrolytic nitrocarburising in an aqueous solution of glycerol (8 %), ammonium nitrate (5 %) and ammonium chloride (15 %) at 850 °C. Conducting a plasma electrolytic polishing of the surface leads to the removal of a loose part of the oxide layer (predominantly FeO), which affects the reduction the surface roughness of 2 times. The rate of the weight loss of steel in this process is 0.5 mg/s. The corrosion current density in a 3.5 % sodium chloride solution decreases from 41.0 μA/cm2 in an untreated sample to 32.6 μA/cm2 in the steel after nitrocarburising and polishing during 30 s and to 22–24 μA/cm2 when the second operation lasted 60-300 s due to the protective action of the nitride zone and the dense part of the oxide layer. Wear test shows that plasma electrolytic polishing enhances the wear resistance of a nitrocarburised sample by 1.8 times.

Distinctive features of electric current passing through vapour gaseous envelope in anodic plasma electrolytic processes

This article focuses on the study of the effect of anodic composition of electrolyte on electric conductivity of a vapour gaseous envelope, formed in the mode of anode stationary heating. The investigation methods were based on measuring current-voltage characteristics in aqueous solutions of ammonium chloride, chlorohydric acid and hydrobromic acid at equal anion concentrations. It has been established that conductivity in vapour gas medium is primarily determined by electric field intensity which varies depending on its composition and thickness, ion mobility considered as factor of secondary importance. It has been assumed that emissive capacity of aqueous solutions can be limited by a critical concentration of their components.

An An Analysis of Crystalline Admixtures in Terms of Their Influence on the Resistance of Cementitious Composites to Aggressive Environments

This paper describes the influence of crystalline admixtures on the chemical resistance of cement composites exposed to aggressive environments. The effect of the crystalline admixtures was determined by a series of physical-mechanical and innovative physical-chemical methods. Specifically, this concerned the measurement of flexural strength, compressive strength, determination of the dynamic modulus of elasticity by the ultrasonic pulse velocity test, and an analysis of the internal structure by mercury intrusion porosimetry and x-ray computed tomography. Physical-chemical analyses were also performed; namely an x-ray diffraction analysis to determine the mineralogical composition and electron microscopy to examine the microstructure. The use of non-destructive testing methods (ultrasonic pulse velocity test and computed tomography) made it possible to compare the properties of the same specimens for 16 months. The specimens were stored in reference laboratory conditions, a sodium sulphate solution and an ammonium chloride solution. The physical-mechanical tests and physical-chemical analyses clearly showed the benefit that crystalline admixtures have for the resistance of cementitious composites attacked by chemically aggressive solutions without affecting the fresh-mixture rheology or decreasing the strength of the composites.

Durability studies on blended cement paste exposed to ammonium chloride environment

The exposure of concrete systems in ammonium based environments can be considered as an aggressive medium which can induce severe and premature deterioration, thus adversely affecting the durability of concrete structures. This paper aims to understand the degradation kinetics of cementitious systems made with Ordinary Portland Cement (OPC) and various combinations of Supplementary Cementitious Materials (SCMs) exposed to chemical grade ammonium chloride (NH4Cl) solution. For this study, the cement paste specimens were exposed to ammonium chloride solution in two different concentrations (1.25 M and 2.5 M) for an exposure duration of two and half months. The kinetics of degradation were evaluated on the basis of changes in mass, visual assessment, changes in thickness and changes in the pH of ammonium chloride solution. Based on the test results, the ternary blended mix with OPC, Ground Granulated Blast Furnace Slag (GGBS) and Silica fume (SF), that is, OPC(50%) - GGBS(40%) - SF(10%) is found to have higher resistance to ammonium chloride attack. The results stress the need to include SCMs and the importance to tailor make the cementitious system for structures exposed to aggressive environment like ammonium chloride.

Mechanical properties of blended cement mortar systems exposed to ammonium chloride environment

There are number of areas where cement composites can be exposed to ammonium based compounds such as agricultural land, chemical fertilizer plants, waste waters, polluted and industrial environments, which can induce severe and premature deterioration of concrete systems. Based on the review of literature, the most common and deleterious ammonium based salts were found to be ammonium nitrate, ammonium chloride and ammonium sulphate. The cementitious systems with Ordinary Portland Cement (OPC) may be attacked easily by these ammonium based chemicals as the OPC hydrates such as Portlandite and C-S-H gel are considered to be unstable in these aggressive media. Thus, it is necessary to understand the alteration kinetics of cementitious systems and the effectiveness of Supplementary Cementitious Materials (SCMs) in improving the resistance when exposed to ammonium based environments for develpoing more durable and sustainable concrete systems. The aim of this experimental study was to investigate the durability aspects in terms of the changes in mechanical properties of cement mortar specimens made with OPC and different combinations of various Supplementary Cementitious Materials (SCMs) exposed to ammonium based salt solution prepared using chemical grade ammonium chloride (NH4Cl). The mortar specimens were exposed to ammonium chloride solution in two different concentrations (1.25 M and 2.5 M) for a maximum exposure duration of two and half months. The SCMs used for the study include Class F Fly ash (FA), Ground Granulated Blast Furnace Slag (GGBS), and Silica fume (SF). The changes in the mechanical properties were evaluated on the basis of visual assessment, depth of penetration, changes in the compressive strength, changes in Ultrasonic Pulse Velocity (UPV) and relative dynamic modulus of elasticity. From all the test results, it can be concluded that the ternary blended mix with OPC, GGBS and Silica fume (OPC-GGBS-SF) has higher resistance to ammonium chloride attack. The results stress the need to include SCMs and the importance to tailor make the concrete for structures exposed to aggressive environment like ammonium chloride.

Ammonia capture with biogas purification from anaerobically digested poultry litter

AbstractBACKGROUNDPoultry litter (PL) has a high solid and organic nitrogen content that is converted into NH3 during anaerobic digestion (AD), requiring the dilution of PL influent prior to AD. With nutrients extracted from the AD effluent, the water could be reused for influent dilution or for other purposes, while creating a designer nutrient product from the PL matrix. The study goal was to determine the effectiveness of an ammonia (NH3)‐stripping and scrubbing system to remove and capture NH3 from anaerobically digested PL. After NH3 stripping, a novel, patent‐pending dual‐vessel NH3‐scrubber system was designed to simultaneously capture the stripped NH3 while producing higher quality biogas through partial removal of non‐combustible carbon dioxide (CO2) and corrosive hydrogen sulfide (H2S).RESULTSThe stripping reactor reduced total ammonia nitrogen (TAN) by 84.6–90.4% when loaded with an ammonium chloride solution or screened PL digestate after 4 h, while the scrubber captured 73.3–76.2% of the stripped NH3 when proxy biogas streams (59–60% CH4, 40% CO2) with two H2S concentrations (0.1 or 1% H2S) were used. The scrubber reduced CO2 and H2S concentrations in the biogas by 3.9% and 23–29%, respectively.CONCLUSIONThe study demonstrated a novel NH3 stripping‐and‐scrubbing system that successfully reduced TAN in anaerobic digestate, captured the stripped NH3, and reduced CO2 and H2S concentrations in biogas. The novel design can be used to increase the adoption of AD for PL by providing a useful NH3 fertilizer, wastewater with less NH3, and a biogas stream with less H2S. © 2020 Society of Chemical Industry (SCI)

Hydrometallurgical stepwise recovery of copper and zinc from smelting slag of waste brass in ammonium chloride solution

A new process for recycling zinc and copper from the smelting slag of waste brass was investigated in this study. The zinc and copper present in the smelting slag were dissolved in a ZnCl2–NH4Cl solution system. To recycle copper, the lixivium was purified by a novel method termed as electrochemistry and chemistry synergetic (ECS) purification. After deep purification of the ECS-treated lixivium by zinc powder cementation, zinc in the lixivium was extracted by electrowinning to obtain a zinc plate. The effects of the leaching temperature, reaction time, and liquid–solid ratio on the extraction percentages of zinc and copper were examined. The results revealed that the extraction percentages of zinc and copper were 88.37% and 90.85%, respectively, at a leaching temperature of 95 °C, reaction time of 90 min, and liquid–solid ratio of 8:1 mL/g. Further, effects of the current density, temperature, and reaction time on the recovery ratio of copper by ECS method were examined. The results revealed that 98.51% of copper could be extracted from the lixivium and that the purity of the extracted copper was 96.7% at a temperature of 70 °C and cathode current density of 75 A/m2 after a reaction for 4 h. In the deep purification process, 0.3 g/L zinc powder was used to completely remove impurities from the ECS-treated lixivium. In the zinc electrowinning process, a current efficiency of 95.79% was achieved at 70 °C and 400 A/m2; the purity of the obtained zinc product was greater than 99.95%, and the direct energy consumption was 2966.59 kW·h/t-Zn.

Corrosion resistance of additively manufactured 316L stainless steel in chloride−thiosulfate environment

In this paper, synergistic effects of chloride (Cl–) and thiosulfate (S2O32–) on corrosion resistance of additively manufactured (AM) and wrought 316L stainless steel (SS) were investigated in ammonium chloride (NH4Cl) solution in the absence and presence of different concentrations of sodium thiosulfate (Na2S2O3). General corrosion induced by Cl– accelerated with the increase of S2O32– concentration for both of the samples. However, pitting resistance of AM 316L SS was found to be at least 4- to 6-fold higher than that of the wrought sample depending on S2O32– concentration. The AM sample demonstrated significantly improved metastable pitting resistance in the presence of S2O32– into Cl– solution. In addition, the passive film of AM 316L SS offered higher charge transfer resistance and film resistance confirming its better stability and barrier characteristics in Cl––S2O32– environment. The superior corrosion resistance of AM 316 L SS compared to wrought sample was attributed to refined microstructure, absence of MnS micro-inclusions, and lack of Cr depleted regions.

Steel Surface Modification by Cathodic Carburizing and Anodic Polishing under Conditions of Electrolytic Plasma

Low-carbon steel (Type 20) is subjected to cathodic carburizing followed by quenching and anodic plasma electrolytic polishing. The structure of the surface layer and its elemental composition are established, and the microhardness distribution within the surface layer, as well as its surface roughness, are measured. The microhardness of the surface layer exceeds 900 HV after carburizing at 900°C for 20 min in a solution containing ammonium chloride and glycerol. It is established that an increase in the surface roughness Ra to 9 μm after cathodic carburizing is related to the formation and destruction of an outer oxide layer. It is shown that the surface roughness can be reduced to 3.5 μm by anodic polishing in a 3% solution of ammonium chloride for 180 s.

Chondroitin sulfate as a green corrosion inhibitor for zinc in 26% ammonium chloride solution: Electrochemical and surface morphological analysis

In the present investigation, Chondroitin sulfate (CS) has been tested as green as a corrosion inhibitor for zinc-carbon battery by using electrochemical impedance spectroscopy (EIS), electrochemical frequency trend modulation (EFTM) and potentiodynamic polarization (PDP) measurements. The calculated results suggest that inhibition efficiency is 98.9% at the optimum concentration (200 mg/L) in 26% NH4Cl solution at 308 K. The outcome of EIS indicates that the values of double-layer thickness increased as the CS concentration increased. EFTM suggests in the presence of CS corrosion rate and corrosion current decreased.PDP results reveal that the nature of CS adsorption is mixed with dominantly cathodic.CS adsorption on the zinc surface obeyed the El-Awady adsorption isotherm model. The magnitude of ΔGads supports the chemical nature of CS adsorption. The Scanning electron microscope (SEM), Energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) study supports the presence of CS adsorbed film over the zinc surface.