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Article

M.A. Abd El‐Ghaffar, E.A.M. Youssef and N.M. Ahmed

Historically, paints designed to protect steel and other metals have been formulated using anticorrosive chromate pigments, which are currently under environmental…

Abstract

Historically, paints designed to protect steel and other metals have been formulated using anticorrosive chromate pigments, which are currently under environmental restrictions. During the investigation reported here, various phosphate compounds. The pigments prepared were characterised using a variety of chemical and spectrophotometric methods of analysis including emission atomic absorption, transmission electron microscope, X‐ray diffraction, in addition to thermal gravimetric analysis. The pigments were also evaluated according to relevant international standard testing methods. The phosphates prepared were incorporated into anticorrosive paint formulations, to replace the imported zinc phosphate pigment, containing medium oil alkyd resin, and melamine formaldehyde resin. Paint films obtained were tested in artificial seawater for 28 days for anticorrosion properties. The results indicated that the paint films had good anticorrosive protection properties that could be attributed to the pigments prepared and the resins used.

Details

Pigment & Resin Technology, vol. 33 no. 4
Type: Research Article
ISSN: 0369-9420

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Article

A. Marchese, A. Papo and G. Torriano

Summary Chlorinated rubber primers formulated with active pigments, which are claimed to be non‐toxic and non‐polluting, are investigated; they are designed for the…

Abstract

Summary Chlorinated rubber primers formulated with active pigments, which are claimed to be non‐toxic and non‐polluting, are investigated; they are designed for the protection of ships (above the waterline), port installation, industrial plants, bridges, etc.

Details

Anti-Corrosion Methods and Materials, vol. 23 no. 9
Type: Research Article
ISSN: 0003-5599

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Article

Nivin M. Ahmed

The purpose of this paper is to present a new trend of anticorrosive pigments based on bulk (core) of zinc oxide covered with a surface layer of phosphates.

Abstract

Purpose

The purpose of this paper is to present a new trend of anticorrosive pigments based on bulk (core) of zinc oxide covered with a surface layer of phosphates.

Design/methodology/approach

A new batch of pigments based on core‐shell theory containing a core (bulk) of cheap oxides covered by a layer of phosphates were prepared. These new pigments combined the properties of both components besides being more economically feasible. Simple chemical techniques were used to prepare these pigments. Characterization of these pigments using X‐ray diffraction and scanning electron microscopy was carried out. Evaluation of these pigments using international standard testing methods was estimated. These pigments were incorporated in solvent‐based paint formulations based on medium oil alkyd resin. The physico‐mechanical properties of dry films and their corrosion properties using an accelerated laboratory test in 3.5 percent NaCl for 28 days were tested.

Findings

It was found that those pigments based essentially on zinc oxide covered with a surface layer of phosphates were easily prepared, are economically feasible and can successfully replace original phosphates with similar efficiency in their corrosion protection behaviour.

Practical implications

These pigments can be applied in other polymer composites, e.g. rubber and plastics, as a reinforcing agent.

Originality/value

The prepared pigments 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, e.g. paper, rubber and plastics composites.

Details

Anti-Corrosion Methods and Materials, vol. 55 no. 6
Type: Research Article
ISSN: 0003-5599

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Article

V. Rajasekharan and P. Manisankar

The purpose of this study is to introduce mechanochemically prepared polyaniline anticorrosive additives. In primer coating technology, there is an increasing interest in…

Abstract

Purpose

The purpose of this study is to introduce mechanochemically prepared polyaniline anticorrosive additives. In primer coating technology, there is an increasing interest in the development of efficient anticorrosive additives which replace the conventional inorganic anticorrosive pigments like heavy metal chromates and phosphates normally added to primer paints for the coating on metals. Conducting polymers are found to be better alternatives.

Design/methodology/approach

Polyaniline phosphate is synthesized through solid-state conditions without using any solvent. The synthesized polyaniline phosphate is added in the primer formulation instead of zinc phosphate. Primers with different quantity of zinc phosphate are also formulated and studied for comparison. The comparison between their abilities to control corrosion of carbon steel were done with application of open-circuit potential monitoring, polarization and electrochemical impedance spectroscopy methods in 3.5 per cent NaCl solution.

Findings

Corrosion studies indicate that polyaniline phosphate can improve corrosion protection properties by taking part the passivation processes. The performance of polyaniline phosphate is better than zinc phosphate.

Originality/value

I certify that the results are from our original research and this paper is neither considered for publication elsewhere nor published previously.

Details

Anti-Corrosion Methods and Materials, vol. 61 no. 6
Type: Research Article
ISSN: 0003-5599

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Article

Hassan S. Emira, Alia A. Shakour, Sayed S. Abd El Rehim, Inas A. Saleh and Mohammed A. El‐Hashemy

The purpose of this paper is to report the use of zinc phosphate pigment as a chromate substitute for coatings on non‐ferrous metals (galvanized steel, pure aluminum…

Abstract

Purpose

The purpose of this paper is to report the use of zinc phosphate pigment as a chromate substitute for coatings on non‐ferrous metals (galvanized steel, pure aluminum, α‐brass and pure copper).

Design/methodology/approach

Paint systems based on zinc chromate and zinc phosphate pigments were prepared. The paints were tested for their physico‐mechanical properties. Testing of the anticorrosive properties of the zinc phosphate pigment in comparison with zinc chromate pigment was carried out by accelerated corrosion exposure, i.e. immersion in 3.5 percent salt solution and exposure for one year at five outdoor stations.

Findings

The possibility of replacing chromate pigment was assessed and the “gap“ observable between the performance of zinc chromate and zinc phosphate pigments was noted.

Originality/value

The non‐toxic inhibitive pigment, zinc phosphate, incorporated into a plasticized‐chlorinated rubber binder, could be applied successfully for the protection of non‐ferrous substrates.

Details

Anti-Corrosion Methods and Materials, vol. 59 no. 3
Type: Research Article
ISSN: 0003-5599

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Article

Nivin M. Ahmed and Mohamed M. Selim

The purpose of this paper is to introduce a new method of pigment preparation, which is economic and highly efficient in corrosion protection properties, known as the…

Abstract

Purpose

The purpose of this paper is to introduce a new method of pigment preparation, which is economic and highly efficient in corrosion protection properties, known as the core‐shell method. According to this method, a cheap core (an extender) is covered with only a surface layer of effective pigments. Following this method of preparation, a new group of pigments is prepared in this research using the Egyptian kaolin ore as the core covered with single and mixed zinc, magnesium, and zinc‐magnesium phosphates as a shell to replace the original phosphates. These new pigments combine the properties of both its core and shell counter‐parts exhibiting improved corrosion protection properties that exceed both of kaolin and zinc phosphate individually.

Design/methodology/approach

Pigments concerned in this paper are prepared using simple chemical techniques, and then they are characterised using X‐ray diffraction, scanning electron microscopy combined with energy‐dispersive X‐ray analysis, and transmission electron microscopy. These pigments are incorporated in solvent‐based paint formulations based on medium oil alkyd resin. The physico‐mechanical properties of dry films and their corrosion properties are tested using accelerated laboratory test in 3.5 percent NaCl for 28 days, according to ASTM.

Findings

The prepared kaolin‐phosphate (core‐shell) pigments are based essentially on Egyptian kaolin ore, which is an abundant cheap ore in Egypt, and then the kaolin is covered with a surface layer of phosphates that are proved to be efficient anticorrosive pigments. These pigments are easily prepared, economically feasible and can successfully replace ordinary phosphate pigments with superior corrosion protection behaviour.

Practical implications

These pigments can be applied in other polymer composites, e.g. rubber and plastics as reinforcing agent.

Originality/value

Prepared pigments are environmentally friendly and can replace hazardous pigments (e.g. chromates) and ordinary phosphates. The main advantages of these pigments are that they combine both the properties of their core and shell counter‐parts, and they are of lower cost with similar and maybe in some cases better efficiency in corrosion protection of metals. Also, they can be applied in industries other than paints, e.g. paper, rubber and plastics composites.

Details

Pigment & Resin Technology, vol. 39 no. 1
Type: Research Article
ISSN: 0369-9420

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Article

L.S. Hernández, B. del Amo and R. Romagnoli

Substitution of zinc chromate or zinc yellow, traditionally used as anticorrosive pigment, for other phosphate‐based pigments that are not hazardous to health and have the…

Abstract

Substitution of zinc chromate or zinc yellow, traditionally used as anticorrosive pigment, for other phosphate‐based pigments that are not hazardous to health and have the same anticorrosive behaviour or even better, is studied in this paper. Four alkyd paints were specially prepared; two of them contained calcium acid phosphate or micronised zinc phosphate as anticorrosive pigments respectively. A paint containing zinc chromate was used as reference and a paint without anticorrosive pigments was used as a blank, in which the other ingredients were increased proportionally to attain the desired PVC relationship. The corrosion behaviour of low carbon steel panels coated with these paints in a 3 per cent NaCl solution was assessed by electrochemical impedance spectroscopy (EIS). In addition, other painted panels were evaluated by salt spray and humidity chamber tests. Results of all tests showed that the paint with calcium acid phosphate and especially that with micronised zinc phosphate exhibited better behaviour than paint with zinc chromate. Analysis of impedance parameters (ionic resistance and capacitance of the paint film) against immersion time allowed the paints to be ranked in the same order as that obtained with salt spray and humidity chamber tests.

Details

Anti-Corrosion Methods and Materials, vol. 46 no. 3
Type: Research Article
ISSN: 0003-5599

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Article

A. Kalendová

The paper studies the effect of modification of zinc orthophosphate on the anticorrosion efficiency thereof in organic coating. The zinc orthophosphate dihydrate and…

Abstract

The paper studies the effect of modification of zinc orthophosphate on the anticorrosion efficiency thereof in organic coating. The zinc orthophosphate dihydrate and tetrahydrate and the reaction of phosphate anion with hydroxyl binder groups are compared. The highest anticorrosion efficiency is reached with pigments which are modified by organic corrosion inhibitors. The highly water soluble phosphate pigments reduce the anticorrosion coating properties. The effect of cation in phosphate pigments on the corrosion inhibition was confirmed.

Details

Pigment & Resin Technology, vol. 31 no. 6
Type: Research Article
ISSN: 0369-9420

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Article

A. Kalendová

The paper deals with the study of modified phosphate compounds and their anticorrosion action when incorporated in paints. The pigments commence as zinc orthophosphate…

Abstract

The paper deals with the study of modified phosphate compounds and their anticorrosion action when incorporated in paints. The pigments commence as zinc orthophosphate, the modification of which can give phosphosilicates, phosphomolybdates, or basic phosphates. With respect to cations, the combination of zinc with calcium, strontium, barium, or aluminium, is possible. The modified anticorrosive pigments differ in their water solubility, inhibition efficiency of the aqueous extracts, and anticorrosion action, when incorporated in organic coatings. Nine types of modified phosphates were studied. The effect in coatings of organic inhibitor in the presence of anticorrosive inorganic pigments was determined.

Details

Anti-Corrosion Methods and Materials, vol. 49 no. 5
Type: Research Article
ISSN: 0003-5599

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Article

P. Puomi, H.M. Fagerholm, J.B. Rosenholm and R. Sipilä

The performance of different pretreatment‐primer systems for hot‐dip galvanized (HDG) and Galfan coated steel has been studied. The materials were pretreated with three…

Abstract

The performance of different pretreatment‐primer systems for hot‐dip galvanized (HDG) and Galfan coated steel has been studied. The materials were pretreated with three pretreatment processes; an alkaline oxide pretreatment with either a chromate or a zirconium based post‐rinse, and a zinc phosphating pretreatment. After the pretreatment, the panels were coated with four commercially available primers. The chemically treated substrates were characterized by using ESCA and GD‐OES, and the cured paint films by using FTIR. Paint adhesion of primed panels was determined with a combined cross‐cut and impact test and also with the NMP test. Formability of the panels was tested by T‐bend test and corrosion resistance with a cyclic prohesion test. According to the prohesion test results, primed Galfan coated panels have better edge corrosion resistance than primed HDG panels. Test results also show that the effect of pre‐treatment is not as significant for the corrosion resistance as the effect of primer. However, in the case of zinc phosphated samples, excellent synergistics between the pretreatment and two of the primers was detected.

Details

Anti-Corrosion Methods and Materials, vol. 46 no. 3
Type: Research Article
ISSN: 0003-5599

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