Hydrochloric Acid Environment Research Articles

Schinopsis lorentzii Extract As a Green Corrosion Inhibitor for Low Carbon Steel in 1 M HCl Solution

The corrosion inhibition of low carbon steel in 1 M HCl solution with different concentrations of Schinopsis lorentzii extract was studied using Tafel extrapolation, linear polarization, and electrochemical impedance spectroscopy (EIS). It was found that Schinopsis lorentzii extract acted as slightly cathodic inhibitor and inhibition efficiencies increased with the increase of extract concentration. The adsorption of the molecules of the extract on the low carbon steel surface was in accordance with the Temkin adsorption isotherm. The results showed that Schinopsis lorentzii extract could serve as a corrosion inhibitor of the low carbon steel in hydrochloric acid environment.

Facile Synthesis of Dodecatungstophosphoric Acid @ TiO2 Pillared Montmorillonite and Its Effectual Exploitation Towards Solvent Free Esterification of Acetic Acid with n-Butanol

An acid activated montmorillonite, treated with organic cationic surfactant, i.e. cetyltrimethylammonium bromide (CTAB), was used as a template to prepare TiO2 pillared montmorillonite taking titanium ethoxide as titania precursor in hydrochloric acid environment. The pillared montmorillonite was further promoted by dodecatungstophosphoric acid impregnation. The as prepared materials were characterized by various spectroscopic and analytical characterization techniques. The catalyst was employed towards a solvent free esterification of acetic acid with n-butanol. The catalyst showed excellent results with 88% conversion and 100% butyl acetate selectivity. It can be recovered and reused readily, making product isolation and catalyst reuse simple. Dodecatungstophosphoric acid impregnated TiO2 pillared montmorillonite was synthesized in a facile technique. The catalyst is found to be robust enough to accomplish high degree of esterification in a clean and green environment.

Electrochemical hydrogenation and corrosion studies of Ti‐48Al‐2Cr‐2Nb alloy in acidic solution

PurposeThe aim of this paper is to investigate the effect of cathodic charging and corrosion behavior of Ti‐48Al‐2Cr‐2Nb alloy in hydrochloric acid solutions.Design/methodology/approachTiAl alloy specimens of thickness 0.5 mm were cathodically charged in 0.1 M HCl solution at room temperature. The prominent current densities selected for this investigation were 25 and 50 mA cm−2 for durations of 24‐120 h. The change in weight of the specimen after charging was measured by a microbalance with an accuracy of ±1 μg.FindingsThe nature of the specimen surfaces was characterized by X‐ray diffraction (XRD), auger electron spectroscopy (AES) and scanning electron microscopy (SEM) equipped with energy dispersive X‐ray spectroscopy (EDS). XRD revealed the phase transformation from microcrystalline to nano‐crystalline, particularly after high charging times (120 h) and high current density (50 mA cm−2). AES and EDS further assessed the compositional fluctuations on both cathodically charged and potentiodynamically polarized specimens. Surface corrosion leading to the generation of microcracks throughout the surface region was observed by SEM. Cathodic charging and the polarization process were responsible for embrittlement and pitting. Decreases in both weight and Vickers hardness values with an increase in charging time revealed that surface erosion depended strongly upon charging density.Originality/valueThe results presented in this work shed light on the role of alloying elements the passive behavior and their implications on their stability in hydrochloric acid environments.

Effect of menthol coated craft paper on corrosion of copper in HCl environment

Natural menthol was coated on craft paper by impregnation and studied as volatile corrosion inhibitor for copper in hydrochloric acid environment. The effect of menthol on copper corrosion was studied by gravimetric and electrochemical methods such as potentiodynamic polarization and electrochemical impedance measurements. The results indicate that menthol adsorbs on the metal surface, which protects copper against further corrosion. The adsorption behaviour of menthol on copper surface was found to obey Temkin’s adsorption isotherm.

Synthesis and characterization of TiO 2-pillared Romanian clay and their application for azoic dyes photodegradation

The synthesis and properties of metal oxide pillared cationic clays (PILCs) has been subject to numerous studies in the last decades. In order to obtain TiO 2-pillared type materials, sodium montmorillonite from Romania–areal of Valea Chioarului, having the following composition (% wt): SiO 2-72.87; Al 2O 3-14.5; MgO-2.15; Fe 2O 3-1.13; Na 2O-0.60; K 2O-0.60; CaO-0.90; PC-5.70 and cation exchange capacity, determined by ammonium acetate method, of 82 meq/100 g, as matrix, was used. Sodium form of the clay was modified, primarily, by intercalation of cetyl-trimethylammonium cations between negatively charged layers which will lead to the expantion of the interlayer space. For the preparation of the TiO 2-pillared clay, the alkoxide molecules, as titania precursor, were adsorbed onto/into clay samples (1 mmol Ti/g clay), in hydrochloric acid environment, the resulted species being converted into TiO 2 pillars by calcination. The as-prepared materials have been used as catalysts for Congo Red dye photodegradation, under UV. The photocatalytic activity of the pillared clays is a function of TiO 2 pillars size, their increase leading to the enhancement of the contact areas between dye solution and photoactive species present in the interlayer space. The structural characteristics and properties of the obtained materials were investigated by X-ray Diffraction, Thermogravimetry Analysis, UV–vis Diffuse Reflectance, Transmission Electron Microscopy and Energy Dispersive X-ray Analysis.

Influence of Solution pH, Anion Concentration, and Temperature on the Corrosion Properties of Alloy 22

We introduce an acid addition technique for the rapid assessment of the influence of solution pH, anion (such as chloride) concentration, and temperature on the dissolution of metals. We demonstrate the technique with the characterization of the dissolution of alloy 22 (Ni–22Cr–13Mo–3W–3Fe) exposed to chloride-containing hydrochloric, sulfuric, and nitric acid environments as a function of pH (from pH 5 to pH ) and temperature (25–90°C). A combination of electrochemical techniques (electrochemical impedance spectroscopy and linear polarization resistance) and atomic force microscopy are used to characterize the influence of the various solutions on the dissolution of alloy 22. Below 50°C, corrosion rates are less than independent of acid type, pH, and temperature. In contrast, between 50°C and the upper explored limit of 90°C, dissolution rates in sulfuric and hydrochloric acid scale approximately linearly with temperature at rates that depend on the solution pH. In nitric acid, corrosion rates are lower at comparable pH values due to the oxidizing effects of nitrates. An increase in the open-circuit potential in conjunction with electrochemical impedance spectroscopy data suggests that nitrates promote a stable passive oxide film that inhibits alloy dissolution in all environments tested.

Corrosion Protection of Mild Steel with Polyaniline–Thiokol Rubber Composite Coatings

The anti-corrosion performance of polyaniline-thiokol rubber (PANI/TR) composite coating applied to mild steel samples in artificial brine and hydrochloric acid environments is for the first time evaluated in this paper. The PANI/TR composite -coatings on mild steel were electropolymerized in a nonaqueous solution. EDS, XPS and SEM were concurrently used to characterize the structure, as well as composition of the coating and show that the structure is favorable to the corrosion protection. Both potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) demonstrated that the PANI/TR coating outperforms PANI coating both in the adhesion to the substrate and its corrosion protection, making the free corrosion potential by about 100mV more positive. As a result, the mild steel corrosion was greatly impeded by applying PANI/TR composite conductive polymer coating.

Polyaniline and polyaniline–thiokol rubber composite coatings for the corrosion protection of mild steel

The anti-corrosion performance of polyaniline–thiokol rubber (PANI/TR) composite coating covered on mild steel exposed to artificial brine and hydrochloric acid environments was evaluated for the first time. The PANI/TR composite coatings were electropolymerized and deposited on mild steel in a nonaqueous solution. EDS, XPS and SEM were all used to characterize the structure as well as the component of the PANI/TR composite coating, which has indicated that its structure would be favorable to the corrosion protection. The results of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) demonstrated that the PANI/TR coating was much better than polyaniline (PANI) coating both in the adhesion to the mild steel substrate and in the corrosion protection. The corrosion potential was about 100 mV more positive for the substrate coated with PANI/TR film than that with PANI. As a result, the corrosion of mild steel can be inhibited greatly by using the PANI/TR composite conductive polymer as a protective layer.

Influence of environment on delayed failure of alumina ceramics

Subcritical crack growth in alumina ceramics is a phenomenon that arouses interest with respect to the problems of performance of various engineering parts, e.g. seal rings, bearings, etc. The subcritical crack growth results in dependence of strength on time known as delayed failure. Effect of environment on subcritical crack-growth exponent for various alumina-base ceramics is studied. A dynamic fatigue technique is utilized. It is revealed that the subcritical crack-growth resistance of glass-bonded aluminas is significantly lower than that of high-purity alumina in air and in water. Only negligible difference was revealed in the delayed failure behaviour of ceramics bonded with various common glassy phases. However, high-purity alumina ceramics are much more susceptible to fatiguing in an acidic environment compared to the yttria-alumosilicate glass-bonded alumina: hydrochloric acid environment reduces drastically the crack-growth velocity exponent due to the low stress–corrosion resistance of magnesia-enriched interfaces in high-alumina ceramics.

High-performance concrete mix for an optimum protection in acidic conditions

High-performance concrete mixes, made with 10% silica fume and various percentages of pulvarized fly ash as an ordinary Portland cement replacement, were prepared and subjected to sulphuric and hydrochloric acid environments. This research was conducted in order to study the effect of various levels of replacement materials and to obtain the optimum mix possessing a maximum protection against acid attack. The parameter investigated was the time, in weeks, taken to cause 20% weight loss of fully-immersed concrete specimens in a 1% solution of sulphuric acid and the same amount of loss in a 1% solution of hydrochloric acid. The investigation indicated that the concrete consisting of 10% silica fume and a maximum of 60% pulvarized fly ash as an ordinary Portland cement replacement showed an optimum protection in the acidic environment.

Corrosion protection of mild steel by coatings containing polyaniline

The anti-corrosion performance of polyaniline coated mild steel samples exposed to artificial brine and dilute hydrochloric acid environments was evaluated. Samples of mild steel (UNS G10100) coated with polyaniline deposited from solution, and overcoated with an epoxy barrier paint, when scratched to expose precise areas of bare metal, exhibited corrosion rates in aqueous 3.5% NaCl solutions 2 times less, and in 0.1 N HCl solutions, 100 times less than observed on identical samples coated with epoxy paint alone. Mechanistic information, and quantitative corrosion rates were obtained by Tafel Extrapolation, Potentiodynamic Polarization, Galvanic Coupling and Electrochemical Impedance Spectroscopic techniques. These studies, in conjunction with surface analysis by ESCA and Auger techniques, indicate that the corrosion protection, even for exposed bare steel areas, occurs by the formation of passivating iron oxide (γ - Fe 2O 3 and Fe 3O 4) surface layers. The formation of these specific oxide layers occurs when the polyaniline is galvanically coupled to the steel. This is evident by the fact that the dimensions of the exposed bare steel area that can be protected in a scratch can be large, but are limited in each corrosion environment.

Atomic Force And Scanning Electron Microscopy Of Corrosion And Fatigue Of An Aluminum-Copper Alloy

AbstractThe morphological features of 2024-T3 aluminum alloy were delineated using atomic force microscopy (AFM) during separate and combined actions of corrosion and fatigue.In-situ AFM corrosion studies in hydrochloric acid environments without mechanical deformation showed accelerated dissolution in the vicinity of second phase precipitates leading to intergranular corrosion. During fatigue in air, AFM images revealed steps along grain boundaries, as well as parallel extrusions and intrusions during the early stages of fatigue life. At later stages of mechanical deformation persistent slip bands (PSBs) were observed on the sample's surface. Cracks were observed to nucleate and propagate along PSBs. For experiments where samples were subjected to the simultaneous action of a corrosive environment and mechanical deformation, intergranular cracking was observed during the early stages of fatigue life. The corrosive environment was observed to accelerate the crack nucleation process.

Stress corrosion cracking of GRP pultruded rods in acid environments

Stress corrosion cracking of GRP pultruded rods has been investigated in 0.0001 to 5.0 N hydrochloric acid environments under bending and tensile loading modes. Crack initiation takes place at exposed glass fibres in the surface of the rod, and crack propagation is planar and at right angles to the rod axis. Leaching of calcium and aluminium from the fibres takes place during the cracking process, and time-to-failure is dependent on the acid concentration, the stress level and the ease of access of the acid to the glass fibre surface. Possible mechanisms of crack propagation through the glass fibres and resin are discussed.