Evaluation of the anticorrosive performance of epoxy coatings containing new core/shell pigments

2018 ◽  
Vol 47 (2) ◽  
pp. 116-126 ◽  
Author(s):  
Nivin M. Ahmed ◽  
Walaa M. Abd El-Gawad ◽  
Eglal M.R. Souaya
Keyword(s):  
Silica Fume ◽  
Active Material ◽  
Core Shell ◽  
Chemical Compositions ◽  
Corrosion Properties ◽  
Fume Silica ◽  
Transmission Electron Microscopy Analysis ◽  
Simple Modification ◽  
Content Type ◽  
X Ray

Purpose Core-shell is structured particles having several chemical compositions. The advantage of these particles arise from their specific design, to be used in decreasing costs by using inexpensive material (natural ore or waste material) as carrier for thin shell of active material. This study aims to prepare ferrites/silica core-shell pigments and compare their inhibition efficiency to original ferrites. These pigments have shells of different ferrites that comprise 10-15 per cent of the prepared pigments on silica fume. Silica fume which is the core is a byproduct in the ferro–silicon industry; this core comprises 85-90 per cent of the prepared pigments. Design/methodology/approach The prepared core-shell pigments were characterized using transmission electron microscopy analysis, energy-dispersive X-ray analysis and sequential wavelength dispersive X-ray fluorescence. These pigments were integrated in epoxy-based paint formulations, and the physical, mechanical and corrosion properties of dry films were examined. The corrosion properties were studied by using immersion test in 3.5 per cent NaCl for 28 days. Findings This study showed that these new eco-friendly and inexpensive pigments are similar to ferrites in their inhibition performance, i.e. they exhibited high corrosion prevention. Research limitations/implications Domestic waste materials were reused in paints and only simple modification was used, and then, their effectiveness showed similar performance to that of the original pigments. Originality/value Ferrite and ferrite/silica pigments are environmentally friendly pigments that can replace other hazardous pigments (e.g. chromates) with almost the same quality in their performance; also, they can be used in industries other than paints (e.g. paper, rubber and plastics composites).

Employment of new modified ferrite pigments in anticorrosive alkyd-based paints

2014 ◽  
Vol 43 (4) ◽  
pp. 201-211 ◽  
Author(s):  
Nivin M. Ahmed ◽  
Walaa M. Abd El-Gawad ◽  
Elham A. Youssef ◽  
Eglal M. Souaya
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Silica Fume ◽  
Smelting Process ◽  
Core Shell ◽  
Testing Methods ◽  
Corrosion Properties ◽  
Content Type ◽  
X Ray ◽  
Standard Testing

Purpose – The purpose of this work is to prepare new core-shell pigments based on silca fume waste as core and ferrite pigments in the shell. Silica fume is a byproduct of the smelting process in the ferrosilicon industry. The reduction of high-purity quartz to silicon at temperatures up to 2,000°C produces SiO2 vapours which then oxidize and condense at low-temperature zones to tonnage amounts of tiny particles consisting of non-crystalline silica that is collected and sold rather than being land-filled because nowadays there is increasing environmental concern with regard to excessive volumes of solid waste hazards accumulation. Silica has no direct effect in protecting metals from corrosion, but on precipitating an effective anticorrosive pigment like ferrite on its surface with low concentrations, this can bring out new core-shell pigment with good anticorrosive performance and low cost. The new pigments will be constructed on a waste silica fume core comprising 80-85 per cent of its chemical structure and the ferrite shell that will be only about 20-15 per cent. These pigments are represented as efficient, economically feasible and eco-friendly. Design/methodology/approach – The different ferrites and ferrites/SiO2 pigments were characterized using different analytical and spectro-photometric techniques, such as X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray and transmission electron microscopy (TEM). Evaluation of these pigments was done using international standard testing methods american standard testing methods (ASTM). After evaluation, the pigments were incorporated in solvent-based paint formulations based on medium oil-modified soya-bean-dehydrated castor oil alkyd resin. The physico-mechanical properties of dry films and their corrosion properties using accelerated laboratory test in 3.5 per cent sodium chloride for 28 days were determined. Findings – The results of this work revealed that ferrite/SiO2 core-shell pigments were close in their performance to that of the ferrite pigments in protection of steel, and at the same time, they verified good physico-mechanical properties. Practical implications – As silica fume has a large array of uses, these pigments can be applied in various industries such as painting, wooding coating, anti-corruption coating, powder coating, architectural paint and waterproof paints. Originality/value – Ferrite, ferrite/SiO2 are environmentally friendly pigments which can impart high anticorrosive behaviour to paint films with concomitant cost savings.

New eco-friendly anticorrosive core-shell pigments

2015 ◽  
Vol 44 (5) ◽  
pp. 276-291 ◽  
Author(s):  
Nivin M Ahmed ◽  
Walaa M. Abd El-Gawad ◽  
Elham A. Youssef ◽  
Eglal R. Souaya
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Ceramic Composites ◽  
Core Shell ◽  
Chemical Compositions ◽  
Corrosion Properties ◽  
Content Type ◽  
X Ray ◽  
Transmission Electron ◽  
Steel Substrates

Purpose – The purpose of this paper is to present the preparation of core-shell ferrites/kaolin pigments and comparing their efficiency in protecting metal substrates to original ferrites which were also prepared. Core-shell structured particles are recently gaining lots of importance due to their exciting applications in different fields; these particles are constructed from cores and shells of different chemical compositions which show ultimately distinctive properties of varied materials different from their counterparts. The new core-shell pigment is based on shell of different ferrites that comprises only 10-20 per cent of the whole pigment on kaolin (cores) which is a cheap and abundant ore that comprises 80-90 per cent of the prepared pigment. The new pigments do not only comprise two different components, but they also contain pigment and extender in the same compound; their loadings in the paint formulations ranges from 50 and 75 per cent of the whole pigment. The work showed that these eco-friendly and cheap core-shell pigments are comparable in their efficiency to that of ferrites in protecting steel substrates. Design/methodology/approach – The different ferrites and ferrites/kaolin pigments were characterized using different analytical and spectrophotometric techniques, such as X-ray fluorescence, X-ray diffraction (XRD), scanning electron microscopy/energy-dispersive X-ray (SEM/EDAX) and transmission electron microscopy (TEM). Evaluation of these pigments was done using international standard testing methods (ASTM). After evaluation, the pigments were incorporated in solvent-based paint formulations based on medium oil-modified soya-bean dehydrated castor oil alkyd resin. The physico-mechanical properties of dry films and their corrosion properties using accelerated laboratory test in 3.5 per cent NaCl for 28 days were determined. Findings – The results of this work revealed that ferrite/kaolin core-shell pigments were close in their performance to that of the ferrite pigments in protection of steel, and at the same time, they verified good physico-mechanical properties. Practical implications – Treated kaolin can be applied in many industries beside pigment manufacture and paint formulations; it can be applied as reinforcing filler in rubber, plastics and ceramic composites. Also, it is applied in paper filling, paper coatings and electrical insulation. Originality/value – Ferrite and ferrite/kaolin are environmentally friendly and can replace other hazardous pigments (e.g. chromates) with almost the same quality in their performance; also, they can be used in industries other than paints, for example paper, rubber and plastics composites.

Study on the corrosion protection performance of new ferrite/kaolin core-shell pigments in epoxy-based paints

2015 ◽  
Vol 63 (1) ◽  
pp. 36-46 ◽  
Author(s):  
Nivin M Ahmed ◽  
Walaa M. Abd El-Gawad ◽  
Eglal R. Souaya
Keyword(s):  
Mechanical Properties ◽  
Corrosion Protection ◽  
Cost Savings ◽  
Core Shell ◽  
Corrosion Properties ◽  
Content Type ◽  
X Ray ◽  
Transmission Electron ◽  
Paint Films ◽  
Steel Substrates

Purpose – The purpose of this study is to prepare core-shell ferrites/kaolin pigments and compare their efficiency in protecting metal substrates to original ferrites. The new pigments are based on precipitating a shell of different ferrites that comprise only 10-20 per cent of the whole pigment on kaolin (core), which is a cheap and abundant ore comprising 80-90 per cent of the prepared pigment. These new pigments combine the properties of both its core and shell counter-parts, exhibiting improved corrosion protection properties. Furthermore, the pigments are represented as efficient, economically feasible and eco-friendly with comparable efficiency to that of original ferrites in protecting steel substrates. Design/methodology/approach – The new pigments were characterized using different analytical and spectrophotometric techniques, e.g. transmission electron microscopy, energy-dispersive X-ray analysis and X-ray fluorescence. The pigments were then incorporated in epoxy-based paint formulations. The physico-mechanical properties of dry films and their corrosion properties were tested using accelerated laboratory tests in 3.5 per cent NaCl for 28 days. Findings – The results of this study revealed that ferrite/kaolin core-shell pigments performance was almost close to that of the ferrite pigments in the protection of steel, and, at the same time, they confirmed good physico-mechanical properties. Practical implications – These pigments can be applied in other polymer composites, e.g. rubber and plastics, as fillers and reinforcing agents. Originality/value – Ferrite and ferrite/kaolin are environmentally friendly pigments, and they can impart high anticorrosive behavior to paint films with concomitant cost savings.

Performance of coatings containing treated silica fume in the corrosion protection of reinforced concrete

2018 ◽  
Vol 47 (4) ◽  
pp. 350-359 ◽  
Author(s):  
Nivin M. Ahmed ◽  
Mostafa G. Mohamed ◽  
Reham H. Tammam ◽  
Mohamed R. Mabrouk
Keyword(s):  
Reinforced Concrete ◽  
Silica Fume ◽  
Corrosion Protection ◽  
Electrochemical Impedance ◽  
Electrochemical Techniques ◽  
Dual Function ◽  
Core Shell ◽  
Protection Efficiency ◽  
Content Type ◽  
Anticorrosive Pigments

Purpose This study aims to apply novel anticorrosive pigments containing silica fume-phosphates (Si-Ph), which were prepared using core-shell technique by covering 80-90 per cent silica fume (core) with 10-20 per cent phosphates (shell) previously, to play dual functions simultaneously as anticorrosive pigments in coating formulations and as an anticorrosive admixture in concrete even if it is not present in the concrete itself. Two comparisons were held out to show the results of coatings on rebars containing core-shell pigments in concrete, and concrete admixtured with silica fume can perform a dual function as anticorrosive pigment and concrete admixture. The evaluation of corrosion protection efficiency of coatings containing core-shell pigments and those containing phosphates was performed. Design/methodology/approach Simple chemical techniques were used to prepare core-shell pigments, and their characterization was carried out in a previous work. These pigments were incorporated in solvent-based paint formulations based on epoxy resin. Different electrochemical techniques such as open-circuit potential and electrochemical impedance spectroscopy were used to evaluate the anticorrosive efficiency of the new pigments. Findings The electrochemical measurements showed that concrete containing coated rebars with core-shell pigments exhibited almost similar results to that of concrete admixtured with silica fume. Also, the anticorrosive performance of coatings containing Si-Ph pigments offered protection efficiency almost similar to that of phosphates, proving that these new pigments can perform both roles as anticorrosive pigment and concrete admixture. Originality/value Although the new Si-Ph pigments contain more than 80 per cent waste material, its performance can be compared to original phosphate pigments in the reinforced concrete.

scholarly journals Effects of Mo Concentration on the Structural and Corrosion Properties of Cu–Alloy

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1307
Author(s):  
Oscar Hernández ◽  
Claudio Aguilar ◽  
Ariosto Medina
Keyword(s):  
Mechanical Alloying ◽  
Load Transfer ◽  
High Energy ◽  
Corrosion Properties ◽  
Transmission Electron Microscopy Analysis ◽  
X Ray ◽  
Electrochemical Tests ◽  
Cu Alloy ◽  
Transmission Electron ◽  
Electron Microscopy Analysis

Mechanical Alloying (MA) has the ability to extend the solubility limits of immiscible alloys in a solid state. In this work, a Cu-10 wt% Mo alloy was synthesized by mechanical alloying, using a high-energy mill type SPEX. The X-ray diffraction and Rietveld results show a crystallite size of 24 and 22 nm of Cu and Mo, respectively, with an occupation value of Mo inside the Cu structure of 27%, which was identificated by Energy Dispersive X-ray Spectroscopy and High-Resolution Transmission Electron Microscopy analysis. After that, the alloy was sinterized in an oven, heating the alloy to 1000 °C—close to the melting point of Cu (1085 °C). Electrochemical tests were carried out under a saline environment of synthetic seawater. The results show that the polarization curve of the alloy showed a pitting corrosion at about 134.83 mV, as well as a repasivation phenomenon (Erp = 241.47 mV) in the cathodic branch. Finally, three time constants were observed in the Nyquist diagrams: formation of a corrosion product film, load transfer, and diffusion, indicating that the corrosion properties in this alloy were improved compared with other Cu–alloys.

Enhancement of styrene-butadiene rubber composites using kaolin covered with metal oxide pigments

2015 ◽  
Vol 44 (2) ◽  
pp. 57-73 ◽  
Author(s):  
Salwa H El-Sabbagh ◽  
Nivin M. Ahmed
Keyword(s):  
Electron Microscopy ◽  
Thermal Properties ◽  
Metal Oxide ◽  
Styrene Butadiene Rubber ◽  
Core Shell ◽  
Butadiene Rubber ◽  
Rubber Composites ◽  
Content Type ◽  
X Ray ◽  
Styrene Butadiene

Purpose – This paper aims to express in detail the rheological, morphological and thermal properties of unpigmented and pigmented styrene-butadiene rubber composites with new prepared inorganic pigment based on kaolin covered with a thin layer of calcium and magnesium oxides or mixed oxide of both together. These new pigments combine the properties of both their constituents (kaolin and metal oxides), which are a new trend in inorganic pigments called core-shell pigments. The pigments used for comparison are kaolin (K), CaO/kaolin (CaO/K), MgO/kaolin (MgO/K) and CaO.MgO/kaolin (CaO.MgO/K). Design/methodology/approach – The different pigments were characterized using different analytical and spectrophotometric techniques, such as X-ray diffraction, scanning electron microscopy/energy dispersive X-ray and transmission electron microscopy, while rubber vulcanizates' rheological, morphological, swelling and thermal properties were examined using different standard and instrumental testing and methods. Findings – The study revealed that there is a significant effect of the new prepared pigments on SBR properties, where the optimum pigment loading was 40 phr for CaO/kaolin, while it was 2.5 phr for MgO/kaolin. Studying the effect of different ratios of oxides on kaolin (5, 10 and 20 per cent), different loadings of these pigments ranging between 2.5 and 40 phr were done for each pigment. These modified kaolin or core-shell metal oxide/kaolin pigments imparted new and improved reinforcing properties to SBR vulcanizates. Research limitations/implications – No research limitations were found. Practical implications – Core-shell MgO/kaolin pigments are eco-friendly and can replace other expensive pigments that are usually used as fillers in the rubber industry with less expenses and comparable efficiency. Originality/value – These new pigments are cheap and efficient and can be used in different fields other than rubber.

scholarly journals Purification and Characterization of the [NiFe]-Hydrogenase of Shewanella oneidensis MR-1

2011 ◽  
Vol 77 (16) ◽  
pp. 5584-5590 ◽  
Author(s):  
Liang Shi ◽  
Sara M. Belchik ◽  
Andrew E. Plymale ◽  
Steve Heald ◽  
Alice C. Dohnalkova ◽  
...  
Keyword(s):  
Methyl Viologen ◽  
Shewanella Oneidensis ◽  
Tris Buffer ◽  
Transmission Electron Microscopy Analysis ◽  
Content Type ◽  
X Ray ◽  
Hepes Buffer ◽  
Transmission Electron ◽  
Genes Encoding ◽  
Electron Microscopy Analysis

ABSTRACTShewanella oneidensisMR-1 possesses a periplasmic [NiFe]-hydrogenase (MR-1 [NiFe]-H2ase) that has been implicated in H2production and oxidation as well as technetium [Tc(VII)] reduction. To characterize the roles of MR-1 [NiFe]-H2ase in these proposed reactions, the genes encoding both subunits of MR-1 [NiFe]-H2ase were cloned and then expressed in an MR-1 mutant withouthyaBandhydAgenes. Expression of recombinant MR-1 [NiFe]-H2ase intransrestored the mutant's ability to produce H2at 37% of that for the wild type. Following purification, MR-1 [NiFe]-H2ase coupled H2oxidation to reduction of Tc(VII)O4−and methyl viologen. Change of the buffers used affected MR-1 [NiFe]-H2ase-mediated reduction of Tc(VII)O4−but not methyl viologen. Under the conditions tested, all Tc(VII)O4−used was reduced in Tris buffer, while in HEPES buffer, only 20% of Tc(VII)O4−was reduced. The reduced products were soluble in Tris buffer but insoluble in HEPES buffer. Transmission electron microscopy analysis revealed that Tc precipitates reduced in HEPES buffer were aggregates of crystallites with diameters of ∼5 nm. Measurements with X-ray absorption near-edge spectroscopy revealed that the reduction products were a mixture of Tc(IV) and Tc(V) in Tris buffer but only Tc(IV) in HEPES buffer. Measurements with extended X-ray adsorption fine structure showed that while the Tc bonding environment in Tris buffer could not be determined, the Tc(IV) product in HEPES buffer was very similar to Tc(IV)O2·nH2O, which was also the product of Tc(VII)O4−reduction by MR-1 cells. These results shows for the first time that MR-1 [NiFe]-H2ase catalyzes Tc(VII)O4−reduction directly by coupling to H2oxidation.

Effect of temperature and pressure on mechanical, surface and electrochemical properties of Al-1.5Cu-5.5Zn-2.5Mg (Alumix-431)

2018 ◽  
Vol 65 (6) ◽  
pp. 558-571 ◽  
Author(s):  
Ayşe Nur Acar ◽  
Rasiha Nefise Mutlu ◽  
Abdul Kadir Ekşi ◽  
Ahmet Ekicibil ◽  
Birgül Yazıcı
Keyword(s):  
Electrochemical Properties ◽  
Surface Characterization ◽  
Electrochemical Impedance ◽  
Effect Of Temperature ◽  
Corrosion Properties ◽  
Content Type ◽  
X Ray ◽  
Good Surface ◽  
Mechanical Properties And Corrosion ◽  
Mechanical Surface

Purpose The purpose of this paper is to examine new alloys created from Alumix 431 powder and investigate their mechanical and electrochemical properties. Design/methodology/approach In this study; Alumix-431 alloy samples were prepared using the powder metallurgy (P/M) method applying cold (RT) and warm (50°C and 80°C) compaction methods under pressures of 200 and 250 MPa and were sintered at 600°C in N2(g) atmosphere. Hardness and density of the samples were measured, and corrosion properties were determined by electrochemical impedance spectroscopy charting polarization curves. Surface characterization was determined by contact angle, scanning electron microscopy/mapping, energy dispersive X-ray spectrometry and X-ray diffractometry images. Findings Alumix-431 alloys obtained upon compaction at 250 MPa/50 °C had the highest mechanical properties and corrosion resistance and good surface properties. On the surfaces of Alumix-431 alloys, α-Al, MgZn2, Al2,CuMg, Al2,O3, Al2MgO4 phases were recorded. Originality/value This study aimed to construct a correlation between mechanical and electrochemical properties of the newly created alloys (prepared under special conditions).

Preparation and Characterization of HGM-Ni0.5Co0.5Fe2O4 Core-Shell Particles by Homogeneous Coprecipitation

2013 ◽  
Vol 745-746 ◽  
pp. 293-297 ◽  
Author(s):  
Mei Yu ◽  
Jing Zhi Hu ◽  
Jian Hua Liu ◽  
Song Mei Li
Keyword(s):  
Spinel Ferrite ◽  
Magnetic Film ◽  
Core Shell ◽  
Chemical Compositions ◽  
Hollow Glass Microsphere ◽  
X Ray Diffraction ◽  
X Ray ◽  
Coprecipitation Process ◽  
Shell Particles

HGM-Ni0.5Co0.5Fe2O4 core-shell particles were prepared by plating Ni0.5Co0.5Fe2O4 magnetic film on hollow glass microsphere (HGM) from the aqueous solution containing NiCl2·6H2O, FeCl2·4H2O, CoCl2·6H2O and HGMs without sintering. Urea was used as precipitator, and air was used as oxidizer in homogeneous coprecipitation process. The morphologies, phase structures, shell thickness, chemical compositions and magnetic performances of the core-shell particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and vibrating sample magnetometer (VSM), respectively. The results showed that a compact and continuous film with thickness at about 250 nm was coated on the HGM by the homogeneous coprecipitation process. The film was spinel ferrite phase, and was determined as the Ni0.5Co0.5Fe2O4. The saturation magnetization (Ms) and the coercivity (Hc) of as-synthesized HGM-Ni0.5Co0.5Fe2O4 core-shell particles were 20.886emu/g and 97.174G, respectively.

Electrodeposition of Pr-Mg-Ni ternary alloy films from the choline chloride-urea ionic liquid and their corrosion properties

2018 ◽  
Vol 65 (5) ◽  
pp. 437-443
Author(s):  
Miao Li ◽  
Bi Qing Chen ◽  
Min He ◽  
Tongtong Xiong ◽  
Lixia Gao
Keyword(s):  
Ionic Liquid ◽  
Ternary Alloy ◽  
Concentration Ratio ◽  
Deposition Time ◽  
Choline Chloride ◽  
Alloy Coating ◽  
Corrosion Properties ◽  
Alloy Films ◽  
Content Type ◽  
X Ray

Purpose This paper aims to obtain rare earth magnesium alloy with good adhesion and corrosion resistance. Design/methodology/approach In 353 K oil bath, cyclic voltammetry was used to study the electrochemical behavior of Pr(III), Mg(II) and Ni(II) in choline chloride-urea ionic liquid. The constant potential method was adopted for electrodeposition of Pr-Mg-Ni ternary alloy films. The content of Pr in the Pr-Mg-Ni alloy films changes with respect to the deposition potential, deposition time and concentration ratio of Pr3+:Mg2+:Ni2+. Response surface methodology was applied to optimize the conditions for obtaining high-quality deposition films. Findings The results showed that the reaction of Ni(II) to Ni is irreversible; this result can be verified by Tafel polarization curve and chronocoulometry curve. Its transfer coefficient on the platinum electrode of 0.32 and diffusion coefficient is 1.0510−6 cm2.s−1. Mg(II) and Pr(III) cannot solely be reduced to their elemental form, but they can be induced via codeposition by Ni(II). The result shows that under a voltage of −1.00 V, the alloy coating with even structure is obtained when the concentration ratio of Pr3+:Mg2+:Ni2+ is 1:1:1 and the deposition time is 20 min. Scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and other analyses revealed that the alloy coating is amorphous. Polarization curves of the cathode are tested, which manifest the lowest corrosion current density, stating which has good corrosion performance in alkaline solution and NaCl solution; this can be attributed to its dense film structure and good combination with the substrate. Originality/value It provides some technology for the production of corrosion-resistant materials.

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