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Article
Publication date: 11 January 2011

A. Miszczyk and K. Darowicki

The purpose of this paper is to report the electrochemical verification of anticorrosive properties of NiZn ferrites as pigments in protective coatings and evaluation of their…

4278

Abstract

Purpose

The purpose of this paper is to report the electrochemical verification of anticorrosive properties of NiZn ferrites as pigments in protective coatings and evaluation of their microwave absorbing properties.

Design/methodology/approach

Ferrites, represented by formula NixZn(1−x)Fe2O4, where x=0, 0.2, 0.4, 0.6, 0.8, 1.0, were synthesized using a ceramic method. The samples of ferrites were examined by X‐ray diffraction and SEM. Immersion tests in ferrite extracts, combined with electrochemical tests using techniques such as polarization curves, linear polarization and electrochemical impedance spectroscopy (EIS) were involved to determine the protective action provided by the ferrites. Epoxy coatings containing 10 vol.% of the ferrite were investigated using EIS. Experimental verification is provided of the microwave attenuation capability of coatings containing the investigated ferrites. Reflection loss, measured in the frequency range of 6.5‐15 GHz, exhibited maximum attenuation at a level of 8‐16 dB.

Findings

The results obtained suggest that NiZn ferrites possess active anticorrosive properties and support inhibition of the cathodic reaction by scale deposition at the metal substrate in an alkaline environment created by the pigments and the cathodic reaction. Additionally, they can serve as a microwave suppressor.

Practical implications

NiZn pigments can be used in coatings to serve simultaneously as an active anticorrosion, non‐toxic pigment and a material protecting against electromagnetic interference problems.

Originality/value

The paper provides information regarding the anticorrosive properties of NiZn ferrites as pigments for protective coatings and also microwave absorbing materials. An attempt was made to elucidate the potential mechanism of anticorrosive action of these pigments.

Details

Anti-Corrosion Methods and Materials, vol. 58 no. 1
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 1 April 2006

Furen Xiao, Bo Liao, Guiying Qiao, Chunling Zhang, Yiyin Shan, Yong Zhong and Ke Yang

As an optimal microstructure of pipeline steels, acicular ferrite is widely found in steels used in oil and gas pipeline transportation because it possesses both high strength and…

Abstract

As an optimal microstructure of pipeline steels, acicular ferrite is widely found in steels used in oil and gas pipeline transportation because it possesses both high strength and good toughness. In this paper, the microstructure of acicular ferrite and its continuous cooling transformation (CCT) diagrams of six steels with different carbon and alloy additions have been studied by using dilatometry, optical metallography. And the effects of different hot deformation processes on the CCT diagrams and microstructures have also been studied. Furthermore, the effects of microalloyed elements and hot deformation on continuous cooling transformation have been discussed. The results show that lower carbon content and alloy additions such as Mn, Nb, Ti, Mo, Ni and/or Cu in steels will promote the formation of acicular ferrite. The hot deformation promotes the acicular ferrite transformation and refines the microstructures of final products.

Details

Multidiscipline Modeling in Materials and Structures, vol. 2 no. 4
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 11 April 2022

Yaojie Zheng, Huili Sun, Luchun Yan, Huisheng Yang, Kewei Gao, Xiaolu Pang and Alex A. Volinsky

The purpose of this study is to investigate the effect of ferrite on hydrogen embrittlement (HE) of the 17-4PH stainless steels.

Abstract

Purpose

The purpose of this study is to investigate the effect of ferrite on hydrogen embrittlement (HE) of the 17-4PH stainless steels.

Design/methodology/approach

The effects of ferrite on HE of the 17-4PH stainless steels were investigated by observing microstructure and conducting slow-strain-rate tensile tests and hydrogen permeability tests.

Findings

The microstructure of the ferrite-bearing sample is lath martensite and banded ferrite, and the ferrite-free sample is lath martensite. After hydrogen charging, the plasticity of the two steels is significantly reduced, along with the tensile strength of the ferrite-free sample. The HE susceptibility of the ferrite-bearing sample is significantly lower than the ferrite-free steel, and the primary fracture modes gradually evolved from typical dimple to quasi-cleavage and intergranular cracking. After aging at 480°C for 4 h and hydrogen charging for 12 h, the 40.9% HE susceptibility of ferrite-bearing samples was the lowest. In addition, the hydrogen permeation tests show that ferrite is a fast diffusion channel for hydrogen, and the ferrite-bearing samples have higher effective hydrogen diffusivity and lower hydrogen concentration.

Originality/value

There are a few studies of the ferrite effect on the HE properties of martensitic precipitation hardening stainless steel.

Details

Anti-Corrosion Methods and Materials, vol. 69 no. 3
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 1 July 2014

Nivin M. Ahmed, Walaa M. Abd El-Gawad, Elham A. Youssef and Eglal M. Souaya

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…

Abstract

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.

Details

Pigment & Resin Technology, vol. 43 no. 4
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 2 May 2017

Nivin M. Ahmed, Walaa M. Abd El-Gawad, Ahmed A. El_Shami and Eglal M.R. Souaya

This study aims to synthesize a series of new anticorrosive pigments using a new technique called “core-shell”. This technique is based on depositing thin surface layer of…

Abstract

Purpose

This study aims to synthesize a series of new anticorrosive pigments using a new technique called “core-shell”. This technique is based on depositing thin surface layer of expensive, efficient anticorrosive pigment on a cheap extender. This extender forms the bulk of the new pigments. The new pigments were constructed on cores of either waste silica fume or kaolin comprising 80-85 per cent of their chemical structure, and the ferrite shell was about of 20-15 per cent. Electrochemical studies were undertaken on two series of pigments for comparison between ferrites/silica fume and ferrites/kaolin pigment to show their performance, as the shells are different.

Design/methodology/approach

The different ferrites/silica fume and ferrites/kaolin pigments were characterized using different analytical and spectrophotometric techniques, such as X-ray fluorescence (XRF) and transmission electron microscopy (TEM). Immersion test and electrochemical impedance measurements were done in 3.5 per cent NaCl.

Findings

The tests revealed that paint films containing Sr ferrite/silica and Ca ferrite/kaolin were the most effective in corrosion prevention.

Practical implications

Silica fumes have 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. Treated kaolin can be applied in many industries besides pigment manufacture and paint formulations; it can be applied as a reinforcing filler in rubber, plastics and ceramic composites.

Originality/value

The new pigments are considered ecofriendly materials, because using them converts a waste product and a natural ore to useful marketable product, leading to reducing cost and saving the environment at the same time.

Details

Pigment & Resin Technology, vol. 46 no. 3
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 5 March 2018

Nivin M. Ahmed, Walaa M. Abd El-Gawad and Eglal M.R. Souaya

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…

Abstract

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).

Details

Pigment & Resin Technology, vol. 47 no. 2
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 3 June 2020

Mayya Ziganshina, Sergey Stepin, Sergey Karandashov and Veronika Mendelson

The purpose of this paper is to search for toxic anticorrosive pigments’ substitute in protective coatings is one of the important tasks that the specialists in the field of steel…

Abstract

Purpose

The purpose of this paper is to search for toxic anticorrosive pigments’ substitute in protective coatings is one of the important tasks that the specialists in the field of steel corrosion face.

Design/methodology/approach

One of the ways to solve the problem of metal corrosion is to use complex oxides as pigments, which are characterized as low-toxic compounds and possess the ability to inhibit corrosion.

Findings

In the production of ferrites, it is possible to use production waste as raw material, and that makes it possible to reduce the price of the resulting product and solve environmental problems simultaneously.

Originality/value

Permanent growth of world production is accompanied by the increasing environment corrosiveness, associated with the intensification of air, water basin and soil pollution by industrial waste. This, as well as the continuously increasing operated metal stock, has recently made the tendency of metals’ total loss from corrosion steadily increasing. All of this points to the importance of studying corrosion processes and the systematic and effective fight against metal corrosion.

Details

Anti-Corrosion Methods and Materials, vol. 67 no. 4
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 25 September 2018

Ankur V. Bansod, Awanikumar P. Patil and Sourabh Shukla

The purpose of the study is to evaluate Cr-Mn ASS weld using different heat inputs for its microstructure, mechanical properties and electrochemical behavior. The microstructural…

Abstract

Purpose

The purpose of the study is to evaluate Cr-Mn ASS weld using different heat inputs for its microstructure, mechanical properties and electrochemical behavior. The microstructural examination used optical and scanning electron microscopy. It was observed that ferrite content decreases with increasing heat input. The length of dendrites, inter-dendritic space and volume of lathy ferrite increase with increasing heat input. The increasing heat input caused grain coarsening near the fusion boundary and produced wider heat-affected zone (HAZ). It also decreases hardness and tensile strength. This is attributed to formation of more δ ferrite in the weld. The electrochemical evaluation suggested that the δ ferrite helps in improving the pitting potential in 3.5 per cent NaCl solution saturated with CO2. Whereas in 0.5-M H2SO4 + 0.003-M NaF solution, higher passivation current density was observed because of dissolution of dferrite. The interphase corrosion resistance decreased with increasing heat input.

Design/methodology/approach

The Cr-Mn austenitic stainless steel or low-nickel ASS was procured in form of 3-mm sheets in rolled condition. The tungsten inert gas welding was performed at three different heat inputs (100 A, 120 A and 140 A), argon as shielding gas with a flow rate of 15 L/min. Different welded regions were observed using optical microscope and scanning electron microscope. Electrochemicals test were performed in solutions containing 3.5 per cent NaCl with saturated CO2 solution and 0.5 M sulfuric acid + 0.003 M NaF at a scan rate of 0.1667 mV/s at room temperature (30 °C ± 1 °C) using a potentiostat.

Findings

The test steel Cr-Mn ASS is suitable with the selected electrode (308 L) and it produces no defects. Vermicular ferrite and lathy ferrite form in welds of various heat inputs. The increase in heat input reduces the formation of lathy ferrite. The width of HAZ and un-mixed zone increases with increase in heat input. The weld zone of low heat input (LHI) has the highest hardness and tensile strength because of higher δ ferrite content and small grain size in the weld zone. The hardness at high heat input (HHI) is found to be lowest because of grain coarsening in the weld. With increase in δ ferrite, the pitting resistance increases. In 0.5-M sulfuric acid + 0.003-M NaF, the increase in ferrite content reduces the passivation current density. Interphase corrosion resistance increases with increase in δ ferrite content as higher per cent degree of sensitization was observed in LHI welds as compared to medium heat input and HHI welds.

Originality/value

This work focuses on welding of ASS by tungsten inert gas welding at different heat inputs. Welding is a critical process for joining metals in most of the fabrication industries and proper heat input is required for getting desired microstructure in the weld metal. This would highly affect the strength and corrosion behavior of the alloy. This paper would give an understanding of how the change in heat input by tungsten inert gas welding affects the microstructural and corrosion behavior in the weld metal.

Details

Anti-Corrosion Methods and Materials, vol. 65 no. 6
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 10 July 2007

A. Kalendová and D. Veselý

To synthesise anticorrosion pigments of a lamellar and core‐shell type based on Zn, Ca and Mg ferrites for metal protecting paints.

1504

Abstract

Purpose

To synthesise anticorrosion pigments of a lamellar and core‐shell type based on Zn, Ca and Mg ferrites for metal protecting paints.

Design/methodology/approach

The anticorrosion pigments were synthesised from oxides or carbonates at high temperature. The pigments synthesised had particles with a pronounced lamellar‐tubular shape consisting of MgFe2O4; Mg0.8Zn0.2Fe2O4; Mg0.6Zn0.4Fe2O4; Mg0.4Zn0.6Fe2O4; Mg0.2Zn0.8Fe2O4; ZnFe2O4; Ca0.2Zn0.8Fe2O4; and CaFe2O4. The other type of synthesised ferrite pigments were core‐shell anticorrosion pigments where a layer corresponding to the compositions including MgFe2O4/KAl3Si3O11; Mg0.8Zn0.2Fe2O4/KAl3Si3O11; Mg0.6Zn0.4Fe2O4/KAl3Si3O11; Mg0.4Zn0.6Fe2O4/KAl3Si3O11; Mg0.2Zn0.8Fe2O4/KAl3Si3O11; ZnFe2O4/KAl3Si3O11; Ca0.2Zn0.8Fe2O4/KAl3Si3O11; and CaFe2O4/KAl3Si3O11 was applied onto the core – white mica – by a chemical reaction. The pigments prepared were characterised by means of X‐ray diffraction analysis, particle size distribution measurement, and scanning electron microscopy. The anticorrosion pigments synthesised were used to formulate alkyd paints that were tested in corrosion atmospheres.

Findings

Lamellar particles were detected in the pigments prepared, whereas quality coverage of the core was identified in the core‐shell ferrites. Good anticorrosion efficiency was detected in all of the pigments synthesised.

Practical implications

The pigments synthesised can be conveniently utilised in paints to protect metal bases from corrosion.

Originality/value

The method of using the ferrites synthesised as metal protecting anticorrosion paints is new. Of great benefit are the application and the method of synthesising the anticorrosion pigments that do not contain any heavy metals and are environmentally friendly.

Details

Pigment & Resin Technology, vol. 36 no. 4
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 31 December 2015

Nivin M Ahmed, Walaa M. Abd El-Gawad and Eglal R. Souaya

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…

Abstract

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.

Details

Anti-Corrosion Methods and Materials, vol. 63 no. 1
Type: Research Article
ISSN: 0003-5599

Keywords

11 – 20 of 908