The 26th Annual Conference - Corrosion Challenges In Industry

[*] Corresponding author. Tel.: +91 99868 90235; fax: +91 821 4241004/5

E-mail address: badeea7@yahoo.com (Badiea Abdullah M.). An Engineer in the general administratin for production,

fields development, PEPA

Stainless steels do not corrode everyday, but when they do, it can be a challenge to determine the cause of failure. In this paper a technical explanation of why the material failed is presented throughout two failure cases.The first case is a network of S/S tubes which suffered severe pitting corrosion in a very mild industrial atmosphere (KORAYMAT Power Station). The second case was a S/S soft water tank that was pitted in an unusual manner after short time in service.The second failure case required more attention to the material integrity rather than the effect of a corrosive environment. The problem is worth to be exposed to the scientific community expecting similar failure cases.

Effect of Dissolved Gases (O₂, CO₂ and H₂S) on the Performance of Corrosion Inhibitors in Petroleum Fields

The use of corrosion inhibitors is the main method for corrosion mitigation in petroleum fields. Corrosion monitoring in these fields usually records variations in the corrosion rates during same inhibitor treatments. This is generally attributed to changes in the fluid compositions, e.g. oil type, oil / water ratio, water salinity and dissolved gases. In this paper, the effect of dissolved gases (O₂, CO₂ and H₂S) on the performance of a number of commercially used inhibitors in petroleum production plants has been investigated.

The corrosion measurements have been conducted on mild steel in synthetic formation water. In the absence of inhibitors, wide variations of the corrosion rate have been recorded under different dissolved gases. Marked changes in the performance of the inhibitors have been also obtained with the variations of gases in water. Significant decrease in the corrosion inhibition occurs in the presence of O₂ alone or with CO₂ + H₂S.

The need for cleaner environment and the rapid depletion of fossil fuels necessitate new technology for energy production. Fuel cells are considered to be the future of power generation. Solid Oxide Fuel Cell (SOFC) is the primary candidate for technological development. However, the major obstacle in commercialization of SOFC is the cost. Dramatic reduction in the material cost would be achieved if interconnects could be fabricated from low-cost commercial steels.

Metallic interconnects have become feasible as a result of reduction in SOFC operating temperature to below 800°C. In this work, ferritic steels with different compositions are developed to be used as interconnects at the cathode side. The performance of these steels at high temperature was investigated where oxidation experiments at 800°C were carried out for more than 1000 hours. The developed alloys were investigated both before and after the oxidation experiment. The change in weight was monitored and the formed oxide layer was studies and analyzed using XRD, SEM, EDX techniques to determine its thickness, composition, structure and base metal structural changes. The relation between the developed alloys composition and the performance at high temperature was evaluated. The effect of the different alloying elements that are used in the developed alloys and the oxidation behaviour at 800°C is studied.

Corrosion inhibition activity of imidazolium and pyridium based ionic liquids

Octavio Olivares-Xometl,^a,*Natalya V. Likhanova,^b M. G. T. Vázquez de los Montero, Noel Nava-Entzana^b

^aBenemerita Universidad Autónoma de Puebla, Facultad de Ingeniería Química, Av. San Claudio, Ciudad Universitaria Col. San Manuel. Puebla, 72570, México.

^bInstituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas No. 152, San Bartolo Atepehuacan, México 07730 D. F.

The effect of 1,3-Dioctadecylimidazolium bromide, 1-Octadecyl-3-methylimidazolium bromide, N-Octadecylpyridinium bromide on the corrosion behavior of mild steel in aqueous sulfuric acid was investigated using weight loss measurements, polarization scans. Surface analyses (SEM, ECS, XPS and FTIR) were carried out to establish the mechanism of corrosion inhibition and composition of the coating, indicated that coating formed by the compounds are favorable to the corrosion protection. The inhibitor efficiency of designed molecules increases by increasing the inhibitor concentration and temperature. The order of inhibition efficiency was correlated with the modification of the molecular structure of inhibitors. The thermodynamic parameters and adsorption processes were determined.

Keywords: mild steel, ionic liquids, corrosion inhibitor, acidic environment.

The electrocatalytic activity of ruthenium modified electrodes in alkaline solution.

The electrocatalytic activity of nickel and titanium silicalite powders pre-soaked in Ru(III) solution was examined towards the electro-oxidation of methanol in KOH solution. It was found that methanol oxidation process starts at the modified NiS-1 electrode once ruthenate species is formed, while the perruthenate acts as the active oxide at the surface of the modified TS-1 electrode. The concentration of the hydroxide ion greatly affects the resulting methanol oxidation current density values at the modified NiS-1 electrode compared to a weak dependence at the modified TS-1 electrode. On the other hand, the order of the oxidation process was estimated as 0.31 and 0.82 with respect to methanol concentration at the modified nickel and titanium silicalites, respectively. The effect of increasing the amount of ruthenium ions introduced by soaking inside the metallic silicalite powders on the methanol oxidation reaction was studied. The increased amount of the ruthenium oxides formed by repeated potential cyclization in KOH solution was found to enhance the methanol oxidation process at the modified NiS-1 electrode. The best construction of the nickel silicalite to the carbon black ratio was observed at 1:3 ratio. Moreover, the catalytic efficiency of the modified nickel silicalite electrode towards methanol oxidation over repeated cyclization is better than that at the modified titanium silicalite one. This catalytic efficiency was improved by incorporation of nickel or cobalt ions together with ruthenium ions in the soaking bath.

Keywords: nickel silicalite, titanium silicalite, electro-oxidation, methanol, ruthenium ions.

Role of some Thiadiazole derivatives as inhibitors for the corrosion of carbon steel in 1 M H₂SO₄

b Chemistry Department, Faculty of Science, Mansoura University, Mansoura-33516, EGYPT

Inhibition of carbon steel corrosion by some Thiadiazole derivatives (I-VI) in 1 M H₂SO₄ investigated by weight loss, potentiodynamic polarization, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) techniques. The presence of these compounds in the solution decreases the double layer capacitance, increases the charge transfer resistance and increases the linear polarization resistance. Polarization studies were carried out at room temperature, and showed that all the compounds studied are mixed type inhibitors with a slight predominance of cathodic character. The effect of temperature on the corrosion inhibition process has been studied and the thermodynamic activation and adsorption parameters were calculated and discussed. Electrochemical impedance was used to investigate the mechanism of corrosion inhibition. The adsorption of the compounds on carbon steel was found to obey Langmuir's adsorption isotherm. The synergistic effect brought about by a combination of the inhibitors and KSCN, KI and KBr was examined and explained. The mechanism of the inhibition process was discussed in the light of the chemical structure and quantum-chemical calculations of the investigated inhibitors.

Key Words: Thiadiazole derivatives; corrosion; carbon steel; 1 M H₂SO₄; quantum-chemical calculations.

Corrosion-hydrogen factor "in-bulk" steel degradation of long term service structures

Karpenko Physico-Mechanical Institute of National Academy of Sciences of Ukraine;

A number of long-term service objects (transit oil and gas pipelines, oil storage tanks, power steam pipilenes, oil refinary reactor shell, oil-hydraulic sets), where the problem of degradation of mechanical, corrosion and corrosion-mechanical “in-bulk” properties is actual, has been considered in the paper. One of a question is a role of working environment in intensification of steel degradation. In this cense the important role of an absorbed by metal hydrogen in an intensifying of in-bulk material degradation by its mutual damages is analyzed. The result of these damages is the revealed phenomenon of an increase after long-term service an elongation at simultaneous decrease of residual area and general material embrittlement what is manifested in a drop of impact strength and fractography decrease of fracture power-intensity. At high temperature service, comparative with creep temperatures, hydrogen, intensifying the diffusion processes, additionally accelerates microstructural changes and creep rate as well.

It is shown that a usage of fracture parameters is very prospective, especially in the conditions of an influence of hydrogenated environment. The characteristic peculiarity of a degradation of high ductile low carbon steels is its sharp decrease of brittle fracture resistance, including an appearance of sensitivity to stress corrosion cracking.

Conclusion has been done that an expertise for an existence of surface defects of corrosion and mechanical nature is insufficient for save service of structures if do not take into consideration of possible degradation of the in-bulk material properties.

Key words: corrosion-hydrogen degradation, carbon and low-alloyed steels, damages

The inhibition effect of 70-30 α brass using inorganic bismuth (III) Chloride (BiCl₃) in 0.1 M HCl at 30^ەC has been assessed by Tafel plots, galvanostatic polarization and scanning electron microscopy (SEM). The addition of very low concentrations of BiCl₃ decreased the cathodic current only which indicate that BiCl₃ behaves as cathodic inhibitor. The decrease in the corrosion rate beside the high efficiency achievement which reached up to 97.3% were attributed to the deposition of Bi metal at zinc locations on the alloy surface. This deposited film is highly persistence as examined in an acid solution without inhibitor by galvanostatic polarization measurements and consequently its suppress the selective leaching of zinc from the alloy surface.

*Institute of Physical Chemistry, Polish Academy of Sciences, 01.224 Warsaw, ul.Kasprzaka 44/52, POLAND

The effect of the sulfate reducing bacteria (SRB) on the hydrogen permeation rate through the ferrite-pearlite and sorbite steels of quite similar chemical composition and the slow strain rate tensile tests were done using the specially designed facilities. Tests were carried out in the synthetic sea water, sterile or inoculated with the bacteria, at potentials corresponding to the cathodic protection (-800 mV to -1400 mV_NCE).

Cathodic polarization within the studied potential range did not stop the metabolism of SRB. Presence of SRB was found to increase the hydrogen permeation rate, to form the S^2- ions, to increase the polarization current, to modify the impedance spectrum and to change the appearance of cathodic deposits in comparison with the sterile conditions. The promoting effect of SRB on the hydrogen uptake was concluded to be the result of the increase in polarization current due to the formation of the less protective layer of cathodic deposits on the steel surface, the presence of S^2- ions and the possible decrease in pH. Despite the similar tendencies, the effect of SRB on hydrogen uptake was more pronounced in the case of sorbite steel. The bacteria action can cause the hydrogen deterioration of steel at potentials, recognized as the safe ones at cathodic protection.

Presence of SRB promoted the plasticity loss, being especially pronounced at potentials -1100 to -1200 mV_SCE. At higher cathodic polarization, the plasticity estimated in inoculated and in sterile water equalizes. The effects have been correlated with the contents of absorbed and of permeable hydrogen. The promotion of hydrogen charging and the plasticity loss by SRB at the low and medium applied cathodic polarization has been accounted for the observed production of S^-2 ions and inhibition of deposit formation. The declining of the SRB effects at the high cathodic polarization has been suggested to be a result of the suppression of the SRB activity due to the high alkalization of the near surface solution. The same amount of hydrogen produces the less detrimental effect on the sorbite than on the ferrite-pearlite steel. However, at the similar cathodic polarization, the sorbite steel absorbs the highest amount of hydrogen and reveals the most pronounced degradation. The effect of structure and sulfide inclusions morphology has been discussed.

The effect of the SRB presence has been also studied in the tests done under the natural Baltic sea conditions. The specially designed, fully equipped and computerized electrochemical double cells for the underwater long term measurements of hydrogen permeation and impedance measurements have been used. Devices have been placed on different depth below the sea water line and have been connected with the data acquisition center situated on the Floating Corrosion Laboratory of the Ship Design and Research Center in Gdynia shipyard. Some devices have been placed close to the cathodically protected walls and at the sea bed. The data obtained during the spring and summer seasons (the 10⁰C and 22⁰ C) have been compared with those obtained in the laboratory tests done in the sterile and SRB inoculated synthetic sea water. The highest hydrogen absorption was detected for in-sea measurements done at summer, which has been accounted for the increased activity of the SRB. No detrimental effects of the presence of the other cathodically polarized structure have been noticed. The hydrogen permeation and the hydrogen embrittlement increased with increase in the sea depth, and especially in the case of the sea bed. The following effects have been considered to explain the above findings: 1) the increased water pressure suppressing the formation of hydrogen gas bubbles on the steel surface, which promoted the hydrogen ingress and 2) presence of the sand particles serving as the abrasives exposing the clean metal surface to the hydrogen and as the places for accumulation of SRB.

Cathodic protection of constructions subjected to the action of SRB in the sea water should provide the conditions, under which no fragment of marine construction could be polarized by potential corresponding to the maximum degradation of the plastic properties of steels (–1100 to –1200 mV_SCE). The higher hydrogen charging occurred under the natural sea conditions in comparison with the measured in the laboratory tests should be taken into account at service of marine constructions, especially the embedded ones.

Effect of Electropolishing Process on the Corrosion Resistance of Stainless Steel 316L in Simulated Body Fluid

Orthopedic implants are mainly made of metals because of their high mechanical properties. Among these metals, stainless steel (SS) 316L which used to make such devices as artificial joints, bone plates, screws and so on. This metal has good mechanical properties, high corrosion resistance, satisfactory biocompatibility and relatively low cost compared with other biomaterial metals. However, chromium, nickel and other alloying elements released from this metal being accumulated in the nearby tissues, due to the aggressive action of the biological fluids. Electropolishing is one of the most important process which improve the corrosion resistance of biomaterial stainless steel. In this study, effects of the main parameters which control the electropolishing process have been examined. As-prepared and used samples in simulated body fluid were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray fluorescence (EDX). The results showed that the corrosion rate and the concentration of the released ions of SS 316L have been markedly decreased.

Key words: Corrosion Resistance, Electropolishing, simulated body fluid, SS 316L.

Passivated titanium as suitable implant in bone surgeries and dental applications.

Waheed A.Badawy et. al.

Chemistry Department, Faculty of Science, Cairo University - Giza, Egypt

Abstract

Porous passive films on Ti have shown excellent biocompatibility and osteoinegrability. The titanium passive films have excellent corrosion resistance in physiological solutions and represent the key for the favorable tissue response to Ti implants. They are now very useful for implantation in human bodies, especially in bone surgeries and dental applications [1, 2]. The physicochemical properties of the passive film are depending on the formation conditions of these films. Recently, porous TiO₂ films with controlled nanostructures were prepared reproducibly and conveniently by potentiostatic anodic polarization of commercially pure titanium in H₂O₂ containing H₂SO₄ solutions [3]. The adsorption of biologically compatible ions, like calcium and phosphate ions, on porous TiO₂, films formed electrochemically on Ti substrates was investigated by electrochemical impedance spectroscopy, EIS, and electron diffraction x-ray, EDX, techniques. The morphology of the formed oxide films and the adsorbed layers on their surfaces was investigated by the scanning electron microscopy, SEM. The experimental impedance data were fitted to theoretical data according to proposed equivalent circuit models. The impedance data fitting enabled the explanation of the structure of the oxide film and the adsorption phenomena occurred on its surface. The film characteristics under different conditions were discussed and the adsorption of Ca²⁺ and PO₄^3- was explained. The results have shown that the oxide films formed potentiostatically on Ti in H₂O₂ containing H₂SO₄ are capable to adsorb biologically compatible ions. The adsorbed layer thickness was found to increase with the increase of concentration of calcium ions present in the ambient electrolyte. The biocompatibility of these materials depends essentially on the apatite-forming ability of TiO₂ due to calcium ion incorporation in the adsorbed films. The formed oxide films with the relatively thick apatite-like adsorbed layer are good implants for bone surgeries and dental applications [4]. Bone volume and bone-implant percentage have been used as parameters to assess the biological potential of implants, evaluating the intrinsic biomechanical properties of bone around implants provide a new approach for assessing and developing implant surfaces for improved osseointegration [5]. Surface modified Ti represents the best implant for such applications.

References:

[1].Velten D, Biehl V, Aubertinetal F 2002 J Biomed Mat Res. 59: 18.

[2] Xiong TY, Cui XY, Kimetal HM 2004 Key Engin Mat 254:375.

[3] El-Serief. RA, Fadl-allah SA, Badawy WA 2007 In:Modern Trends in Physics Research; American Institute of Physics (AIP Conference Proceedings, volume 888, Melville, New York, pp. 110-122.

[4] Badawy WA,. Fathi AM, El-Serief. RA, Fadl-allah SA, Badawy WA 2008 J. Alloys and[5] Butz F, Aita H, Wang CJ, Ogawa T 2006 J Dent Res 85:560.

Keywords: Adsorption, biological compatibility, bone-implant, calcium phosphate, dental applications, titanium oxide.

Electrochemical behavior of AZ91D magnesium alloy

in phosphate medium

F. El-Taib Heakal, A. M. Fekry, M. Z. Fatayerji

Chemistry Department, Faculty of Science, Cairo University

Abstract

The influence of pH on the corrosion behavior of Mg-based AZ91D alloy was investigated in a constant composition phosphate medium using various electrochemical techniques, complemented with surface analysis data. The studied solutions were 0.1 M H₃PO₄, NaH₂PO₄, Na₂HPO₄ and Na₃PO₄ having pH values of 1.8, 4.5, 9.1 and 11.8, respectively. Spontaneous passivation was substantiated from monitoring the continuous positive shift of the open circuit corrosion potential with both immersion time and solution pH. The impedance data indicated more improvement in the insulating properties of the corrosion products formed on the alloy surface with increase in pH. The electrolyte pH plays a determinant influence on surface film properties, as films formed in phosphate solutions with higher pH values are thicker, thus affording better protection for the alloy than those formed in acidic solutions. Good agreement was observed between the results obtained from electrochemical techniques and those from EDX and XRD examinations. The alloy is more susceptible to corrosion in acidic phosphate solutions than in the alkaline ones. Crystalline magnesium (Mg), magnesium hydride (MgH₂) and magnesium oxide (MgO) were found to be the main constituents of the surface film after holding for 2 h in the acidic phosphate medium.

Keywords: AZ91D alloy, phosphate medium, ac-impedance, potentiodynamic, pH.

Electrochemical Evaluation of the New Synthesized Bis-thiourea-succinamide Compound as a Corrosion Inhibitor

N.O.Shaker, N. M. Amer, R. M. Mansour and O.M. Abo-Elenien

Egyptian Petroleum Research Institute (EPRI), 1 Elzhoor Region, box, 11727 Cairo, Egypt.

Abstract

New bis-thiourea-succinamide compound is synthesized purified and confirmed by FT.IR. The inhibition effect of di-thiourea-succinamide compound against carbon steel at inhibitor concentration of 0.0, 100, 200, 300, 400, 500 and 600 ppm in 0.5 M HCl solution has been investigated. The weight losses, open circuit potential (OCP), potentiodynamic polarization of cathodic and anodic tafel region and electrochemical impedance spectroscopy (EIS) methods are applied. Corrosion data, such as corrosion rate (I_corr), corrosion potential (E_corr), corrosion resistance (R_p), coverage surface area (θ) and efficiency (IE %) are determined from every technique through computer program. The weight loss, OPC, Tafel polarization and EIS results indicated that the efficiency is increased with increasing the corrosion inhibitor concentration.

Keywords: carbon steel; inhibitor, electro polarization.

Synthesis and Electrochemical Evaluation of New Bis-(P- Hydroxy Phenyl Diamido) - Butane as Corrosion Inhibitor for Carbon Steel in 1 M Hydrochloric Acid

N.O.Shaker; O. E. El-Azabawy and O. M. Abo-Elenien

Egyptian Petroleum Research Institute (EPRI), Nasr city 11727, Cairo, Egypt

Abstract

Bis-(ρ-hydroxyphenydiamido)-butane has been synthesized, its structure confirmed and evaluated as a corrosion inhibitor. The inhibition concentration at 0.0, 100, 200, 300, 400, 500 and 600 ppm in M HCl solution has been investigated. The weight loss, potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) methods have been applied. The corrosion data such as corrosion rate, corrosion potential (E_corr), corrosion resistance (R_p), coverage surface (θ) and efficiency (IE %) have been determined for each method through a computer program. The morphology of the formed films was also examined by scanning electron microscope.

Keywords: carbon steel; inhibitor and electrochemical polarization.

Ni and Ni-Cu carbon deposits as electrocatalysts in alkaline fuel cells.

Rabab S, Amin, K. M. El-Khatib

Chem. Eng. Department, National Research Center, Dokki, Giza, Egypt

Abstract

Nickel and nickel-copper plated carbon deposits were prepared by using electroless technique in alkaline solution. The effect of varying the conditions of the deposition bath on the properties of the formed deposits was studied. The electrocatalytic activity of C/Ni and C/Ni-Cu electrodes towards methanol oxidation was examined in 0.1 M KOH solution. It was found that increasing the bath temperature increases the activity of the formed deposits reaching its maximum value at 90°C. Moreover, the deposition bath with pH 9 gets the best results, after which the electrocatalytic activity decays gradually. No enhancement was achieved in methanol oxidation current density by adding copper in the deposition bath, however, better efficiency over repeated cyclization was observed. The morphology and the chemical composition of the formed electrodes were shown using SEM and EDX analyses before and after methanol oxidation process.

Effect of Tungsten Electrode Type and Shielding Gas Composition on the Weld Metal Properties of Austenitic Stainless Steel Weldments

A. Sadek*, A. Hussein**, El-Sayed M. El-Banna**, M. Gouda***, H. Abdel-Aleem***, M. Ashour****

ABSTRACT

Nitrogen is increasingly becoming a popular alloying element in austenitic stainless steel. This is due to the remarkable improvements provided by nitrogen to austenitic stainless steel. Nitrogen, as an alloying element, increases the strength, toughness, corrosion resistance, and austenite stability. Nitrogen represents a good substitute for nickel, thereby, reducing alloying elements cost. This study was conducted to make use of these valuable effects of nitrogen in welding of 316L stainless steel. In addition, newly developed tungsten electrodes activated with rare earth metals oxides were used to optimize the welding process.

Welding was done with autogenous automatic gas tungsten arc welding (GTAW) process using bead on plate technique. Nitrogen was introduced to the shielding gas with 10%, 5%, and 3.5% by volume. Pure argon was used for comparison. Ceriated (W+2%Ce₂O₃), Lanthanised (W+2%La₂O₃), and Yttriated (W+2%Y₂O₃) tungsten electrodes were used in addition to the conventional thoriated (W+2%Th₂O₃) tungsten electrode. Properties of weld metal were examined by measuring weld metal area, weld metal hardness, nitrogen content of weld metal, ferrite content, and corrosion resistance. In addition, the hot cracking tendency was investigated.

The results showed that, 3.5% of nitrogen in shielding gas is characterized by a stable arc, deep penetration, and high arc efficiency for all tungsten electrodes. The presence of dissolved nitrogen in weld metal resulted in an increase in weld metal hardness and corrosion resistance without affecting hot cracking tendency.

Among the used tungsten electrodes; the ceriated electrode showed the highest arc efficiency and corrosion resistance of weld metal while the yttriated electrode showed the lowest arc efficiency and corrosion resistance of weld metal.

*Prof. Central Metallurgical R&D Inst., El-aTabbin, Cairo, Egypt

**Prof. Cairo University, Faculty of Engineering, Metallurgical Dept., Cairo, Egypt

*** Researcher, Central Metallurgical R&D Inst., El-aTabbin, Cairo, Egypt

**** Research Assistance, Central Metallurgical R&D Inst., El-aTabbin, Cairo, Egypt

Significance of Welding Defects in Corrosion of Gas Pipelines Weld

H. Abdel Aleem*, K. Hafez*, and A.Sadek**

Abstract

Oil and gas distribution via pipeline requires high level of safety and trust aiming at the reduction of costs, increase of operational efficiency and minimization of accidents. It has been estimated, however, that approximately 40% of the world-wide pipeline network has reached its project life (estimated in 20 years) and efforts have been continually applied to further extend its residual life. The structural integrity evaluation of pipelines is an important tool to minimize the risks of leakage and its impact on the environment,

The spool connecting of X-tree to an 8" diameter sub-sea export pipeline has failed at a girth weld in the 4” nominal bore section adjacent to a 45 degree elbow. The failed spool was received for failure analysis together with data concerning its history, fluid analysis, operating conditions and schematic graph of the spool

The results obtained in this investigation, showed that failure is due to flow enhanced accelerated localized corrosion attack related to improper welding operation of girth welds. Undercut and / or excess bead penetration of root weld bead, and improper heat input could be the primary causes for the localized turbulent flow conditions created around the girth weld and resulting in this accelerated corrosion failure, assisted by thermally stressed HAZ and fusion line.

*Researcher, Central Metallurgical R&D Inst., El-aTabbin, Cairo, Egypt

** Professor, Central Metallurgical R&D Inst., El-aTabbin, Cairo, Egypt

Effect of heat treatment on the mechanical properties and corrosion behavior of steel foam

A. Fathy*, A.M El-Aziz** and E. Saif**

* Central Metallurgical Research and Development Institute(CMRDI), Cairo, Egypt
**German University in Cairo (GUC), Cairo, Egypt.

Abstract:

Metal foams are a class of materials with extremely low densities and an outstanding combination of mechanical, electrical, thermal, and acoustic properties. They offer a large potential for light-weight structures with high stiffness and high mechanical properties, energy absorption, and thermal management. Their extraordinary property combinations make them interesting for applications where more than one function can be met. Steel foam produced by slip reaction foam sintering process (SRFS) had a chemical composition of 1%C, 1.3 %Mn, 0.5% Si and 0.5 % Cr is subjected to many different heat treatment and corrosion conditions.

In the presented work, the effect of different heat treatment conditions was applied to investigate its effect on the mechanical behavior of produced steel foam. Austenizing at 800, 850 and 900 degree Celsius for one hour was applied and tempering at 400, 450 and 500 for one hour respectively was examined. Corrosion characterization for the samples was carried out by using the salt spray test; samples were subjected to marine "corrosive" atmosphere for 54 hours at 40 degrees Celsius and by using the autoclave (high temperature/high pressure) samples were subjected to steam of distilled water at high pressure and high temperature reached 170 degrees Celsius for 96 hours. Compression test was carried out to test and evaluate the mechanical properties for the samples, before and after corrosion tests also before and after heat treatment process.

The results showed that corrosion can negatively affects the mechanical properties of the steel foam, as in the compression test the samples which was not subjected to any of the corrosive atmosphere showed much better results than the samples which was tested in the salt spray or the autoclave test. Not only but also heat treatment process showed a great influence on the mechanical behavior of steel foam, as using different heat treatment cycle, better compression stress could be achieved .

Wear and corrosion characteristics of Al–4.7Si–0.4Mg–0.3 Ti–0.03V alloys and heat treatment influence.

Y. Fouad¹, A.M. El-Aziz¹, Ehab Abd Rahman², A. El zaabalawy¹
¹Department of Engineering and material science, German university in Cairo., Egypt
²Department of Engineering and material science, American university in Cairo., Egypt

Abstract

In present paper, the influence of silicon (wt.%) and precipitation hardening treatment of cast Al–(4.7%)Si–0.4%Mg- 0.3% Ti- 0.03% V alloy on two body abrasive wear behavior has been reported. Alloys under investigation were prepared via foundry route. Cast alloys were subjected to the precipitation hardening treatment following a sequence of solutionizing, quenching and artificial aging. All the alloys were solutionized at 500 °C for 3 h followed by water quenching (25 °C) and aging hardening at 160 and 200 °C for 10 h. Abrasive wear tests were conducted against 100, 320 and 600 grade SiC polishing papers at 3 N contact loads. It was observed that increase in silicon (wt. %) reduced the wear rate. Heat treatment of all the alloys under investigation improved the wear resistance. Precipitation hardening at 200 °C results in better wear resistance than the alloys hardened at 160 °C. Optical microstructure study of alloys in heat treated condition showed that dendrite structure is broken down after the heat treatment and spheroidization of eutectic silicon takes place. Scanning electron microscopy (SEM) of wear surfaces of was carried to analyze the mechanism of material removal under abrasive wear condition. Corrosion behaviour have been studied in 3.5% NaCl, representing higher corrosion rate for the sample age hardening at 200 °C than 160 °C. Same result have been obtained from autoclave test (HAST) and salt spray test-ASTM B287-62.

Corrosion of commercial brass in hot salt environments

B.G. Ateya*, F. M. Al Kharafi, I. M. Ghayad

Chemistry Department, Faculty of Science, Kuwait University, Kuwait

bgateya@yahoo.com

ABSTRACT

Hot concentrated salt solutions are encountered in desalination plants, in the drilling of wells for the production of oil and gas and for the recovery of geothermal energy, in refineries, and in power generation where sea water is used for cooling. In view of the complexity of the selective dissolution of alloys, the results of measurements and the conclusions on dezincification of brass at ambient temperatures and low salt content can not be readily extrapolated to conditions of high temperatures and salt concentrations. The present work addresses the dezincification behavior of commercial brass in hot concentrated brines. Commercial brasses are known to contain more than one phase and to include dezincification inhibitors.

The corrosion of commercial brass was studied using electrochemical techniques, scanning electron microscopy, Energy Dispersive Spectroscopy (EDS) and Inductively Coupled Plasma (ICP). The results of these measurements will be presented and discussed. The implications regarding the integrity of brass under such harsh environments will be explored.

Acknowledgements

The authors acknowledge the support of this work by the Research Administration of Kuwait University, Grant Numbers SC01/05 and GS01/01. They also acknowledge the use of the scanning electron microscope (SEM).

Ni and Ni-Cu carbon deposits as electrocatalysts in alkaline fuel cells.

Rabab S, Amin, K. M. El-Khatib

Chem. Eng. Department, National Research Center, Dokki, Giza, Egypt

Corrosion Behaviour of Tin in Citric Acid Solutions and Effect of Some Inorganic and Organic Compounds

E. E. Foad El Sherbini, A. A. Abdel Aziz and E. Hamed

Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Abbasia,11566, Egypt

Abstract

The electrochemical Behaviour and corrosion of tin in various concentrations of citric acid solutions (0.1 to 1.0 M) has been studied by using cyclic voltametric technique under different experimental conditions. The potentiodynamic anodic polarization curves exhibit active/passive transition. The active dissolution of tin involves one anodic peak. During the active region, tin dissolves as Sn(II), which is oxidized to Sn(IV) to yield either Sn(OH)₄ or SnO₂ on the anode surface. The active dissolution of tin enhances with increasing acid concentration, temperature and scan rate. The cathodic curve exhibits one cathodic peak corresponding to the reduction of passive layer. Addition of Cl^-, Br^- or I^- ions to the citric acid solution enhances the anodic dissolution of tin. The aggressiveness of the halide ions towards the stability of the passive film decreases in the order Cl^-ñ Br^- ñ I^- .

Addition of some polyethylene glycols to citric acid solution decreases the current density of the anodic peak and shifts its peak potential towards the negative direction. These changes depend on the concentration and molecular weight of the polyethylene glycol added.

Keywords: Corrosion, tin, citric acid, halide ions, polyethylene glycol.

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