Corrosion Science

The corrosion inhibitive performance of red mangrove (Rhizophora harrisonii) ethanol extracts on mild steel in 1 M H2SO4 was studied using gravimetric method of analyses. Evaluation of the performance of Rhizophora harrisonii as green corrosion inhibitor for mild steel was carried out using different concentrations (blank, 0.6, 0.8 and 1.0g/l), temperature (303.15, 313.15, 323.15, 333.15 and 343.15), and immersion time (2, 4, 6, 8 and 10 hours) as indices. The results showed that red mangroves (Rhizophora harrisonii) inhibited corrosion of mild steel. Increase in extract concentration increases the inhibition efficiency, whereas increase in temperature reduces inhibition efficiency. Adsorption of components of the plants extract on the mild steel was studied using different adsorption isotherm. Langmuir and Frumkin adsorption isotherm was obeyed with correlation coefficient of 0.85 and 0.99 respectively. The plant's best inhibition efficiency in sulphuric acid medium at 1.0g/L extract was 95.65%. Reduction in corrosion rate indicate that Rhizophora harrisonii may be a good corrosion inhibitor.

Red mangroves (Rhizophora racemosa) work as a good corrosion inhibitor on stressed and unstressed mild steel in phosphoric acid environment. Weight loss method of analyses were used to study the corrosion inhibitive effect of red mangrove (Rhizophora recemosa) extracts on stressed and unstressed mild steel in 1 M H3PO4 acid solution. The effect of inhibitor concentrations (blank, 0.6, 0.8 and 1.0g/l), temperature (303.15, 313.15, 323.15, 333.15 and 343.15), and immersion time (2, 4, 6, 8 and 10 hours) were observed for normal and stressed mild steel. The surface morphologies of stressed and normal mild steel were studied using Scanning Electron Microscopy Zeiss Smart SEM-EDX model. The results showed that Rhizophora racemosa inhibited corrosion in both stressed and normal mild steel. The extracts inhibition efficiency increased as the concentration of the extract increased, but decreased as the temperature increased. The plant's best inhibition efficiency in phosphoric acid medium at 1.0g/L extract was 97.96% for normal mild steel and 96.15% in stressed mild steel at the temperature of 303.15K and 313.15K respectively. Plot of inhibition efficiency against concentration were used to determine Coefficient of Determination (R 2) and Correlation Coefficient (R) on the mild steel. Rhizophora racemosa reduced corrosion in H3PO4 acidic medium with the correlation coefficient of 0.9, therefore, Rhizophora species may be a good inhibitor.

 Oxidized species from high temperature corrosion during refining were identified.  Phase identification by micro-XRD retained spatial information and phase layout.  Troilite content and continuous magnetite layers are key for proper passivation.  Mössbauer complimented XRD data by identifying additional nanocrystalline phases.

Akee apple leaves extract (AALE) was tested for inhibition of corrosion of mild steel in sulphuric acid solution using gravimetric and gasometric measurement. The corrosion of mild steel was investigated at 40-60 0 C in 2M H 2 SO 4 solution. The result of the inhibition revealed AALE efficiently delayed the dissolution of mild steel with inhibition efficiency obtained from gravimetric and gasometric at 60 0 C are 72.19 % and 74.32 % at addition of 0.5 g/l concentration of AALE respectively. The increase in inhibitor (AALE) concentrations results in decrease in corrosion rate and increase in inhibition efficiency. The inhibitive adsorption parameters show the corrosion process followed the Langmuir adsorption isotherm with physical adsorption mechanism. Finally, the kinetic parameters established the corrosion process was endothermic reaction and occurred with spontaneous process.

AbstractÐA physico-mathematical model has been developed, based on the Point Defect Model, to simulate depth pro®les of the alloying and host elements in the passive systems (including barrier and outer ®lms and the metal phase) of binary alloys. Curve ®tting of the XPS depth pro®les for W and Ni in a Ni±W alloy shows that the Point Defect Model can account for the segregation of alloying elements in the passive ®lm on this system. The eects of various parameters on the segregation have been investigated. Most of the predictions of the model are experimentally observed.

A simpli®ed method is proposed for modeling the chemistry and potential distribution in a stress corrosion crack in sensitized stainless steel in boiling water reactor (BWR) coolant environments. The model is based on an assumption that only those species that are present in the largest concentrations in the crevice determine the potential distribution down the crack. The advantage of this method is that it permits simpli®cation of the mathematics and allows predictions to be made of the potential and concentration distributions without knowing various parameters, such as the equilibrium constants for homogeneous chemical reactions in the cavity and diusion coecients of species that are present at relatively low concentrations near the crack tip. In some important cases, analytical expressions can be obtained for the pH, potential near the crack tip, and crack propagation rate. The conditions for which the potential on the crack ¯anks and that in the vicinity of the crack tip coincide with the free corrosion potential in the local environment, and hence, for which there exists a balance between rates of the local anodic and cathodic partial processes, are determined. The impact of the potential drop in the external environment on the potential and concentration distributions down the crack and on the crack propagation rate is also investigated. Excellent agreement is obtained between calculated and measured crack growth rates.

Corrosion management in the oil and gas industry remains a critical challenge due to complex operating conditions such as temperature variations, fluctuating flow rates, and pressure changes. While corrosion cannot be entirely eliminated, the strategic use of inhibitors significantly mitigates internal corrosion through continuous injection. However, no single corrosion inhibitor is universally effective for all environments, necessitating rigorous testing methodologies such as the CO₂ bubble test to assess their performance under specific conditions. In this study, representative produced water samples were collected from key points within the production system, including the test separator, first stage separators A and B, and the electrostatic dehydrator-each located downstream of corrosion inhibitor injection points. The measured corrosion rates (mm/year) for these locations were 0.05, 0.11, 0.08, and 0.06, respectively, with all values meeting the industry target of 0.1 mm/year except for first stage separator A. To address this, the corrosion inhibitor dosing rate for first stage separator A was optimized, ensuring improved inhibitor efficiency and bringing the corrosion rate within the acceptable threshold. The findings highlight the effectiveness of site-specific corrosion inhibitor adjustments in maintaining long-term asset integrity and operational reliability. Regular monitoring and proactive optimization of inhibitor dosing strategies are recommended to sustain corrosion control across all process units.

Volatile corrosion inhibitors (VCIs) are incorporated into packaging paper or film to protect metals against atmospheric corrosion. The vapour pressure determines the equilibrium concentration of a volatile corrosion inhibitor (VCI) in the surrounding atmosphere. However, the rate at which the VCI can be delivered across the air gap to a metal surface is determined by the gas permeability. This is the product of the vapour pressure and the diffusion coefficient: S A = P A D AB . The gas permeability of commercial VCIs was estimated at elevated temperatures from vaporisation rates measured using a simple thermo-gravimetric method (TG).

Corrosion in concrete prevents in-situ observation, necessitating models to provide insight into the local reaction currents. We present a computational method for predicting corrosion rates of reinforcements within concrete under natural conditions, i.e. requiring the corrosion current to be supported by equal cathodic currents. In contrast to typical corrosion models, where these two counteracting currents are required to be co-located, we allow these currents to be separated such that pitting corrosion can be supported by cathodic reactions over a much larger area. Pitting corrosion is investigated, elucidating the effects of the concrete porosity and water saturation, the presence of dissolved oxygen, and chlorine concentration within the pore solution. The presented model is capable of capturing the dynamic growth of acidic regions around corrosion pits, showing the limited region over which the hydrogen evolution reaction occurs and how this region evolves over time. The ability of oxygen to diffuse towards the metal surface due to increased porosity is seen to have a major effect on the corrosion rate, whereas changes in the chlorine concentration (and thus changes in the conductivity of the pore solution) play a secondary role. Furthermore, external oxygen is seen to enhance corrosion but is not required to initialise and sustain acidic corrosion pits.

The application of scanning electrochemical techniques to evaluate and spatially resolve corrosion activity has progressively increased over the last 20 years. Electrochemical scanning techniques are based principally upon the assumption that localised corrosion, where the anodic and cathodic processes take place at separate sites, can be represented as point sources. The electric field generated by sites of localised corrosion consists of equipotential lines which can be measured and graphically represented as a contour map. Many modern day systems use either a static or vibrating reference or quasi-reference electrode, to measure the electric field, more specifically the field normal (perpendicular) to the surface. The latter of these systems, namely the vibrating electrode, allows for improved resolution and a lower minimum detectable signal. The following paper presented here discusses a study conducted to evaluate the influence of the operating parameters on the resolution and minimum detectable signal measurable using a scanning vibrating electrode system. Measurement of the electric field generated at a point source, namely, a gold point in space (PIS) electrode, is used to evaluate the effect of parameters such as probe scan speed, vibration amplitude and probe-sample distance on the peak output potential and the resolution, defined here as the ratio of the peak potential to the full width at half-maximum peak potential (FWHM).

Khoi Tu, Doctor of Philosophy.Thesis ?Enhancing the Performance of Pulsed Current Applied Coatings for Corrosion Protection?, The University of Manchester, 2010.Accelerated Low Water Corrosion (ALWC) is a particularly severe form of microbiologically induced, aggressive and localised form of corrosion. It is most commonly found just above the Lowest Astronomical Tide. The average corrosion rates are typically very high, about 1.0 mm/wetted side/year, so it should be prevented to ensure the lifetime of steel structures in seawater. In this project, in order to deal with ALWC, a pulsed current applied coating, calcareous film, is studied to form after a sequence of electrochemical treatments to clean the corrosion products and kill bacteria. In sea water, calcareous films (deposits of CaCO3 and Mg(OH)2) are produced on steel structures that are cathodically protected. They have two functions: reducing the current demand from the CP system and acting as a protective coating. When depos...

To be able to meet confident requirements for design as well as enhance overall vehicle performance, choosing a magnesium-based alloy for automotive applications necessitates taking into factors including power, resistance to corrosion, castability, and lowering of weight prospects. When choosing a magnesium-based alloy for automotive applications, it's crucial to consider a number of significant variables. In order to ensure that the alloy can bear the necessary load and stresses, its strength and mechanical qualities must first match the exact specifications and requirements of the automobile part. Second, the alloy's capability to resist corrosion is essential since it must survive the effects of the environment and safeguard against deterioration throughout the component's lifecycle. In order to obtain the requisite lightweight attributes for enhanced fuel efficiency, production methods are optimized while taking factors like castability and lightweight potential for reduction into mental clarity. Several automotive applications, including as physique, frame, and inside parts, have utilized magnesium. Instrument clusters, steering wheels, engine cradles, chairs, transfer cases, and countless housings are some examples of Mg applications. By leveraging magnesium's potential for integrating components into single-piece, thin-wall metal castings, these kinds of applications were created mainly to provide lower-mass elements. Applying the "Weighted Aggregated Sum Product Assessment (WASPAS)" method, those making decisions are able to evaluate possibilities based on a wide range of parameters. It involves providing criteria weights, determining scores for every potential and summing the results to determine the most suitable option.

In this paper a procedure on how to estimate the oxide scale growth in superheater and reheater tube utilizing the empirical formulae and the finite element modeling is proposed. An iterative procedure consisting of empirical formulae and numerical simulation is used to determine scale thickness as both temperature and time increase. Results of the scale thickness over period of time for two different design temperatures of the steam and different heat transfer parameters are presented. The procedures may provide better estimation on the oxide scale growth, provided that all the heat transfer parameters are well specified.

This work attempts to give a general zoom to the nanostructured carbon materials from their appearance, discovery and fabrication, until their applications and impacts in the scientific field. The three main carbon nano-allotropes: fullerenes, carbon nanotubes and graphene, are revised in order to stablish a general overview. Finally, some alternatives on the potential growing of these materials are also presented

 At T ≤ 450°C, Ni-rich grains (NiEGs) segregate at the steel/double oxide interface.  At T ≥ 475°C, an internal oxidation zone (IOZ) forms under the double oxide scale.  The IOZ consists of two phases: a Ni-rich fcc phase and an FeCr-spinel phase.  The IOZ growth relies on fast diffusion paths, such as grain and twin boundaries.

This work investigates the compatibility of Zr2AlC MAX phase-based ceramics with liquid LBE, and proposes a mechanism to explain the observed local Zr2AlC/LBE interaction. The ceramics were exposed to oxygen-poor (CO  2.210 -10 mass%), static liquid LBE at 500°C for 1000 h. A new Zr2(Al,Bi,Pb)C MAX phase solid solution formed in-situ in the LBE-affected Zr2AlC grains. Out-of-plane ordering was favorable in the new solid solution, whereby A-layers with high and low-Bi/Pb contents alternated in the crystal structure, in agreement with first-principles calculations. Bulk Zr2(Al,Bi,Pb)C was synthesized by reactive hot pressing to study the crystal structure of the solid solution by neutron diffraction.

 Zinc oxalate coating showed effective protection against corrosion when prepared with low immersion time and conversion bath at temperature ambient.  Better corrosion protection performances were observed to samples treated with 10 -1 M oxalic acid solution.  The zinc corrosion products act as block, forming a barrier protection.  The consumption of the oxalate layer in the electrolytic solution and the enrichment of the corrosion product by Na with corrosion time were observed.

The individual contributions of pH and chloride concentration to the corrosion kinetics of bioabsorbable magnesium (Mg) alloys remain unresolved despite their significant roles as driving factors in Mg corrosion. This study demonstrates and quantifies hitherto unknown separate effects of pH and chloride content on the corrosion of Mg alloys pertinent to biomedical implant applications. The experimental setup designed for this purpose enables the quantification of the dependence of corrosion on pH and chloride concentration. The in vitro tests conclusively demonstrate that variations in chloride concentration, relevant to biomedical applications, have a negligible effect on corrosion kinetics. The findings identify pH as a critical factor in the corrosion of bioabsorbable Mg alloys. A variationally consistent phase-field model is developed for assessing the degradation of Mg alloys in biological fluids. The model accurately predicts the corrosion performance of Mg alloys observed during the experiments, including their dependence on pH and chloride concentration. The capability of the framework to account for mechano-chemical effects during corrosion is demonstrated in practical orthopedic applications considering bioabsorbable Mg alloy implants for bone fracture fixation and porous scaffolds for bone tissue engineering. The strategy has the potential to assess the in vitro and in vivo service life of bioabsorbable Mg-based biomedical devices.

The collapse of reinforced autoclaved aerated concrete (RAAC) panels has attracted considerable public and academic interest. As detailed experimental data are not yet available and replicating the natural corrosion process requires years or decades, computational modelling is essential to understand under which conditions corrosion remains concealed. The very high porosity of RAAC is widely suspected to be a major contributing factor. However, current corrosion-induced cracking models are known to struggle with capturing the role of concrete porosity. To remedy this critical deficiency, we propose to enrich corrosion-induced cracking modelling with the analytical solution of reactive transport equations governing the precipitation of rust and a porosity-dependent description of diffusivity. With this, the corrosion concealment in RAAC panels is studied computationally for the first time, revealing that RAAC panels can suddenly collapse before any warning of corrosion-induced surface cracking and allowing to map the conditions most likely to result in sudden collapse.

Local probe techniques have been largely applied to predict the spatial distribution of the electrochemical reactions and to quantify the corrosion rate. These local probe techniques are now being developed to capture the temporal information, in-situ and in real-time. Nevertheless only few works have been devoted to investigate with these local probes the role of stress on pitting sensitivity on passive materials. In this paper, a part of the most recent studies based on combination of local electrochemical measurements with finite element mapping of surface stress gradients are reported illustrating the role of inclusions under straining and the mechanical effect of surface preparation on pitting sensitivity of stainless steels.

In order to study the passivity breakdown of a type 316L stainless steel, the electrochemical impedance and surface stresses were measured under straining conditions. The Mott-Schottky analysis, performed at high frequency, appears as very useful method to study, below the apparent yield strength, the effects of a mechanical stress on the capacitance values. The results obtained in sodium chloride media indicate that the semiconducting properties of passive films formed in a tensile stress field reflect a higher vacancies concentration than those formed in a stress-free state, suggesting that the passive film conductivity is increased. It was also shown that the Mott-Schottky plots drop in the presence of tensile surface stresses, indicating that the passive film composition may be different from that formed in the presence of compressive surface stresses. A comparison between the effects of mechanical stresses and those of chloride is proposed.

An integrated predictive model is being developed to account for the effects of localized environmental conditions in crevices on the initiation and propagation of pits. A deterministic calculation is used to estimate the accumulation of hydrogen ions (pH suppression) in the crevice solution due to the hydrolysis of dissolved metals. Pit initiation and growth within the crevice is then dealt with by either a probabilistic model, or an equivalent deterministic model. Ultimately, the role of intergranular corrosion will have to be considered. While the strategy presented here is very promising, the integrated model is not yet ready for precise quantitative predictions. Empirical expressions for the rate of penetration based upon experimental crevice corrosion data can be used in the interim period, until the integrated model can be refined. Bounding calculations based upon such empirical expressions can provide important insight into worst-case scenarios.

In this study, the effects of laser shock peening (LSP) on stress corrosion cracking (SCC) behavior of nickel based Alloy 600 in tetrathionate solution were investigated. The LSP induced compressive residual stresses and changes in the near surface microstructure, hardness were characterized. The effects of LSP on SCC susceptibility of Alloy 600 in tetrathionate solution were evaluated by slow strain rate tests and constant load tests. The results indicate a significantly longer time to failure and decreased susceptibility to SCC. These improvements were attributed to LSP induced compressive residual stresses, increased yield strength and hardening caused by near-surface microstructural changes.

Thin passive films formed on highly corrosion-resistant type-312L stainless steel, containing 20 mass% chromium and 6 mass% molybdenum, in 2 mol dm À3 HCl solution at 293 K have been analyzed by glow discharge optical emission spectroscopy (GDOES). The stainless steel does not suffer pitting corrosion even in this aggressive solution, showing a wide passive potential region. The depth profiles obtained clearly show a two-layer structure of the air-formed and passive films: an outer iron-rich layer and an inner layer highly enriched in chromium. Alloy-constituting molybdenum is deficient in the inner layer of the passive films and is enriched in the outer layer, particularly at the active dissolution potential. The molybdenum species in the outer layer may retard the active dissolution of stainless steel, promoting the formation of stable passive films highly enriched in chromium. Chloride ions are present only at the outermost part of the passive films, not penetrating into the interior part.

Spark anodizing of titanium, Ti-6Al-4V and Ti-15V-3Al-3Cr-3Sn in alkaline aluminate electrolyte produces highly crystalline anodic films consisting mainly of Al 2 TiO 5 with aand c-Al 2 O 3 as minor oxide phases, irrespective of substrate composition. However, the apparent efficiency for film formation decreases in the following order: Ti-6Al-4V, titanium and Ti-15V-3Al-3Cr-3Sn. A large amount of aluminium species are incorporated from the electrolyte, probably by plasma-chemical reaction, and become distributed throughout the film thickness. This distribution indicates that the electrolyte penetrates near to the film/substrate interface through the discharge channels. Thus, the outwardly migrating aluminium ions under a high electric field can be present even in the inner part of the anodic films. Voids are developed at the film/substrate interface, particularly on the vanadium-containing alloys, reducing the adhesion of the anodic film to the substrate.

The effect of Pb 2+ on polarization behavior of nickel has been investigated in 0.1 M NaClO 4 + 10 À2 M HClO 4 + x M PbO solutions (x = 0, 10 À5 , 10 À4 , 10 À3 ) at room temperature. The cyclic voltammogram has suggested that Pb 2+ degrades the stability of the passive film on Ni. The corrosion potential of Ni shifted to the more noble direction and the anodic current peak of Ni dissolution decreased with increasing Pb 2+ concentration in solution, indicating that Pb 2+ suppresses significantly the anodic dissolution. The underpotential deposition (UPD) of lead on Ni in the potential range more noble than À0.215 V (SHE) corresponding to the equilibrium potential of the Pb 2+ (10 À3 M)/Pb electrode was confirmed by XPS and GDOES analyses. The anodic Tafel slope, b + , of Ni dissolution changed from b + = 40 mV decade À1 in the absence of Pb 2+ to b + = 17 mV decade À1 in the presence of 10 À4 or 10 À3 M Pb 2+ , which was ascribed to the increase in active sites of Ni surface emerged as a result of electrodesorption of Pb adatoms. The roles of Pb adatoms in active dissolution and active/passive transition of Ni were discussed from the above results.

Crevice corrosion of iron was evaluated using the multichannel electrode method in which ten individual working electrodes (WEs) of pure iron were embedded in resin, placed in an artificial crevice in the range from 0.5 mm to 2.0 mm, and immersed in 0.51 mol dm -3 NaCl solution. The WEs were connected to an electronic circuit which allowed galvanic coupling between them and measurement of their individual coupling current or open circuit potential. Time-transient of the spatial distribution of coupling current and open circuit potential showed sequential transition of the coupling current on WEs at the middle position of the crevice from cathode to anode. The WE near the opening of the crevice initially showed a large anodic current, then a decreasing the anodic current corresponding to the current transition of other WEs, and finally a large cathodic current coupled with the other anodic WEs in the crevice. The transition of coupling current was explained by the change in pH and concentration of dissolved oxygen in the crevice. Thickness of the gap of the artificial crevice affected the transition behavior of coupling current distribution. For example, slower current transition with smaller coupling current was found in the case of a narrower gap. Such properties were related to the introduction and consumption of dissolved oxygen in the crevice solution and the circulation of gap solution from / to the outside of the crevice.

Repassivation behavior of type-312L stainless steel containing 6% of molybdenum was examined in NaCl solution using in situ micro-indentation technique, together with type-304 and 316L stainless steels. High stability of the passive film formed on the type-312L stainless steel was also examined by depth profiling analysis of passive films using glow discharge optical emission spectroscopy (GDOES). In 0.9 mol dm À3 NaCl solution at 296 K the type-304 and 316L stainless steels are passive only up to 0.3 V (SHE), above which pitting corrosion occurs. In contrast, no pitting corrosion occurs on type-312L stainless steel. Despite the significant difference of the pitting corrosion resistance, the repassivation kinetics of the three stainless steels, examined by micro-indentation at 0.3 V (SHE), is similar. The presence of molybdenum in the stainless steel does not influence the repassivation kinetics. The charge required to repassivate the ruptured type-312L stainless steel surface increases approximately linearly with the potential, even though the passivity-maintaining current increased markedly at potentials close to the transpassive region. Repassivation occurs without accompanying significant dissolution of steel, regardless of the stability of passive state. Depth profiling analyses of the passive films on the type-312L stainless steels formed at several potentials revealed that molybdenum species enrich in the outer layer of the passive film, below which chromium-enriched layer is present. The permeation of chloride ions may be impeded by the outer layer containing molybdate, enhancing the resistance against the localized corrosion of the type-312L stainless steel.

еКструзіЯ тіста у КільцевоМу шарі, що зМащЮЄ Розглянуто завдання руху тістової маси в каналі з використанням гідродинамічного мастила. Визначена математична модель динамічного стану в'язкої рідини. Складено рівняння спільної течії. Розроблено спосіб безконтактного формування макаронних виробів, що дозволяє знизити практично до нуля тертя в матрицях макаронного преса. Ключові слова: тістова маса, гідродинамічна змазка, математична модель, в'язка рідина, течія.

Iskenderun Demir Celik Fabrikasi atik maddesi olan curufun yapisi, cozunurlugu ve denizel ortama olasi etkileri, MartTemmuz 2003 tarihleri arasinda arastirilmistir. Bu kapsamda, curufun deniz suyu, saf su, yagmur suyu ve yagmur suyu deniz suyu karisiminda cozunurlugu arastirilmistir. Deniz suyunda, sedimentde, sestonda ve denizel organizmalarda agir metal derisimleri incelenmistir. Curufun cozunurlugunde Standart Yontemler, agir metal analizlerinde AAS ve GFAAS yontemleri kullanilmistir. Curuf dogal kosullarda suda cozunmemistir. Sonuc olarak, Iskenderun Demir Celik fabrikasindaki curuf depolama alaninda curufun yagmur suyu ile cozunmesinin cok zayif bir olasilik oldugu ve deniz suyu, sediment, seston ve denizel organizmalarin agir metal derisim sonuclari, curufun Iskenderun Korfezi icin agir metal kirliligi bakimindan bir kirlilik unsuru olmadigini gostermistir

The molecular dynamic simulation of Na+ + Cl- + H2O and Na+ + Br- +H2O systems were carried out using 72 and 8 molecules of water and Na+ and Cl- (or Br-) ions respectively at 298.15K. It is reported that in case of Na + + Br - +H2O system shows higher aggregation as compared to the Na + + Cl - + H2O which may be due to the higher ionic radii and atomic weight of Br- ions.

This work presents some of the results from the project: ''Effect of the environment on reinforcement durability'' (DURACON) in its first two-years period, which investigates the influence of urban and marine meteorochemical parameters on the performance of reinforced concrete structures. The results presented in this investigation are from 21 marine test sites only (no urban environments are included), distributed among 11 countries (Argentina,

Carbon steel has long been used in storing the saline water that results from oil washing in the oil industry. However, a high corrosion rate is reported, resulting in significant economic losses for oil companies. In the Middle East oil field, the temperature touches 50⁰C in Summer, causing increasing in corrosion rate for saline water steel storage tanks and pipes. In the present work, abundantly available wheat straw was used to prepare a cost-effective silicate inhibitor. The high inhibition efficiency of up to 94 % decreased the corrosion rate from severe corrosion for no-inhibitor specimen to close to low corrosion category for optimum inhibitor concentration specimen. The mechanism of the inhibition effect is the formation of a chemically adsorbed layer on the steel surface, which is successfully described by Langmuir isotherm. Additionally, at high concentrations of nano-silica, complex aggregates might form and be physically adsorbed on the surface of steel above the chemically adsorbed nano-silicate monolayer.

The corrosion behavior of copper in nitric acid with and without the addition of Rcicinus communis oil at various concentrations was investigated with techniques such as weight loss, measurements of electrochemical polarization and electrochemical impedance spectroscopy (SIE). The results obtained show that the copper corrosion rate decreases with the increase in concentration of Rcicinus communis oil to 99% to 250 ppm. Rcicinus communis oil acts as a mixed inhibitor. The effect of temperature on copper corrosion indicates that the effectiveness of inhibition of the natural material remains constant with increasing temperature. The values of inhibition efficiency obtained from weight loss, polarization curves and EIS are in good agreement.

Aluminium-3%Magnesium-10% silicon carbide composite is prepared in an induction heating furnace. The physical characteristics of both as-casted sample and corroded samples have been studied. A slice of the composite sample is kept in sea water for 6 weeks (42 days) and the weight loss was measured with the help of an electronic weighing machine in every 7 days to study the corrosion behavior. © 2016 Elixir All rights reserved. Elixir Materials Science 95 (2016) 40706-40708 Materials Science Available online at www.elixirpublishers.com (Elixir International Journal) S. C. Mishra and Ajit Behera/ Elixir Materials Science 95 (2016) 40706-40708 40707 A hollow spindle which has its stirrer blades attached to motor and V-belt arrangement for better stirring. The plunger rod is attached to perforated capsule which holds the magnesium. Aluminium blocks are melted in the crucible at temperature of 800 °C and stirred at 500 rpm. Magnesium turnings are added one after another through the hollo...

The effect of naturally occurring Emilia Sonchifolia (ES) was investigated as corrosion inhibitor for mild steel in 1.0M H 2 SO 4 using gravimetric measurement at 30 o C and 60 o C. The extract was found to retard corrosion rate of Mild steel. The inhibition efficiency (IE %) increased with increase in concentration of the ES extract up to 74.77% at 1.0 M. Increase in temperature increased the corrosion rate in the absence and presence of inhibitor but decreased the inhibition efficiency. ES was found to obey Langmuir adsorption isotherm and Kinetic-Thermodynamic Model of El-Awady et al. at all the concentrations and temperatures studied. Phenomenon of physical adsorption is proposed from the activation parameters obtained. Thermodynamic parameters reveal that the adsorption process is spontaneous.

The present paper aims to investigate the e ects of three variables of the reactional system that take place in the manganese phosphating process by hot immersion used in Brazilian Army light armaments. The evaluation of the in uence of these variables was carried out with a factorial experimental design with two levels for three variables, namely time, phosphating reagent concentration and ferrous ions concentration in the reaction enviroment. The results showed that the selected variables have signi cant interaction e ects, so they must be evaluated together. It was concluded that: (1) time is important, especially for the mass gain of the coating and for re nement of the crystals; (2) the phosphating reagent concentration proved to have high impact on the well-de ned crystallization of coatings, on the contribution of manganese in crystals and on obtaining higher weight layers; (3) the ferrous ions concentration contributed to the appearance of coarser granulations.

The corrosion behaviour of magnetron sputtered a-and b-Ta coated AISI 4340 steels was studied with potentiodynamic polarization and electrochemical impedance spectroscopy. The coating porosity was observed to decrease with increasing coating thickness. For coatings less than 10 lm thick (a-or b-Ta), porosity was significant and open pores resulted in severe localized corrosion of the steel substrate, coating delamination, and overall coating failure. Additionally, the b-Ta coatings were more susceptible than the a-phase to delamination. As for the 50 and 100 lm thick a-Ta coatings, the electrochemical impedance behaviour was comparable to that of Ta foil, demonstrating the coating viability and corrosion resistance.

During hot rolling process a steel strip covers with oxide scales. These scales have to be removed by acid pickling process. This work focuses on the study of the scale removing rate of a hot-rolled steel strip in order to find an expression explaining the rate of reaction in hydrochloric acid. The study of scale removal is accomplished by utilizing the pickling simulator with different acid concentrations and pickling temperatures. There are two approaches that can be used to find a scale removing rate; the measurement of weight change and the iron concentration change after the pickling process. In this work, the measurement of the change of iron concentration was selected because it represents the actual amount of the scale removed after the pickling process. The experimental data were used to derive the expression for the rate constants. By using these expressions, the pickling equations can be obtained. These equations are capable of predicting the maximum removable scale thick...

This paper presents an analytical study on ferrous reinforcements embedded in binders found in ancient buildings aged from the Gallo-Roman period to the beginning of the 20th c. AD. The study of this kind of archaeological analogues is necessary to improve knowledge on the long-term corrosion behaviour of low carbon steels that could be used in concrete to build the substructure of nuclear wastes storage or reversible disposal facilities. The corrosion system can be described as a multi-layer pattern made of metal, a dense corrosion product layer, a transformed medium and a binder. The morphological, and physico-chemical properties like composition, structure and porosities of each part were studied with different analytical methods like optical and electronical microscopies, Energy Dispersive Spectrometry coupled with Scanning Electron Microscopy, Electron Probe MicroAnalysis, Mercury porosimetry, micro-Raman spectroscopy and micro-Diffraction under Synchrotron Radiation.

Hydantoins substituents have been studied as corrosion inhibitors for mild steel in HNO 3 and NaOH media. The studies involve chemical and electrochemical methods. Weight loss, thermometric and Potentiodynamic polarization (PDP) have been applied. The experimental measurements have been confirmed by quantum chemical calculations and Monte Carlo simulation (MCS). Potentiodynamic polarization studies reveal that the hydantoin derivatives act as mixed type inhibitor. The adsorption obeyed the Temkin adsorption isotherm model. Electronic parameters relevant to their inhibition activity such as EHOMO, ELUMO, Energy gap (ΔE),

AA7075-T6 aluminum alloy is a material that widely used in the aircraft industry because aluminum as a lightweight metal, good machinability, good corrosion resistance and good castability and non-magnetic metals. Aluminum also has high tenacity, is easy to form and is easy to connect. Aluminum has good resistance to corrosion, however aluminum has effect to corrosion if it is on corrosive environment including AA7075-T6 aluminum alloy which used in the aircraft industry. Inhibitor is used to control a corrosion. The aims of these researchs were to investigate the effect of inhibitors on corrosion rates and the rate of fatigue crack corrosion propagation on AA7075-T6 aluminum alloys. This research is used Na2CrO4 inhibitors with variety of concentrations of 0.1%, 0.3%, 0.5% and 0.7% added to 3.5% NaCl solution. Corrosion rate test is used a method of potential dynamic polarization. Corrosion fatigue testing is carried out with constant amplitude at a frequency of 10 Hz and a voltage ratio (R) 0.1. Specimens were used cracked specimen centers (CCT) on orientation in the direction of rolling. The supporting data of the research were the mechanical properties of the material included optical microstructure observation, tensile testing and hardness testing. The results have shown that the optimal concentration of Na2CrO4 inhibitors was achieved at 0.5% which was characterized by a decreasing in corrosion rate and slower corrosion rate of fatigue cracking.

AA7075-T6 aluminum alloy is a material that widely used in the aircraft industry because aluminum as a lightweight metal, good machinability, good corrosion resistance and good castability and non-magnetic metals. Aluminum also has high tenacity, is easy to form and is easy to connect. Aluminum has good resistance to corrosion, however aluminum has effect to corrosion if it is on corrosive environment including AA7075-T6 aluminum alloy which used in the aircraft industry. Inhibitor is used to control a corrosion. The aims of these researchs were to investigate the effect of inhibitors on corrosion rates and the rate of fatigue crack corrosion propagation on AA7075-T6 aluminum alloys. This research is used Na2CrO4 inhibitors with variety of concentrations of 0.1%, 0.3%, 0.5% and 0.7% added to 3.5% NaCl solution. Corrosion rate test is used a method of potential dynamic polarization. Corrosion fatigue testing is carried out with constant amplitude at a frequency of 10 Hz and a voltage...

The effects of dual Zr & N plasma immersion ion implantation (PIII) on the corrosion behavior of WE43Mg alloy are evaluated in simulated body fluid (SBF) and cell culture medium (cDMEM). Zr & N PIII improves the corrosion resistance of WE43 which exhibits smaller i corr , larger R 1 & R 2 , smaller CPE 2 , and larger phase angle maxima in SBF and cDMEM. The Zr & N PIII WE43 samples exhibit 12-folds decrease in i corr in SBF and 71-folds decrease in i corr with near capacitive EIS in cDMEM. Analysis of the corrosion products reveals calcium phosphate.

The effect of temperature and gas composition on the corrosion rate and corrosion byproduct of copper foil was studied by exposing it to sulphur (S 2 ), S 2 + hydrochloric acid (HCl) and hydrogen sulphide. The temperature was varied from 80 to 140 °C. Copper foil reacted with S 2 to form CuS, Cu 9 S 8 and Cu 1.8 S. Corrosion rates ranged from 9.6 µm/h at 110 °C to 0.5 µm/h at 140 °C. The presence of HCl caused pitting and enhanced the corrosion rate above 112 °C. Cu 2 S formed when copper was exposed to hydrogen sulphide gas. Sulphide scale that formed was friable and nonadherent.