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1 – 10 of 166
Article
Publication date: 1 February 2002

R. Romagnoli, R.O. Batic, V.F. Vetere, J.D. Sota, I.T. Lucchini and R.O. Carbonari

Hardened cement paste is a heterogeneous system resulting from the grouping of particles, films, microcrystals and other solid structural elements bounded in a porous…

Abstract

Hardened cement paste is a heterogeneous system resulting from the grouping of particles, films, microcrystals and other solid structural elements bounded in a porous mass. The cement paste microstructure must be understood firstly due to its influence on concrete properties. The behaviour of concrete greatly depends on the conformation of localised special structures rather than on general structures found in the mass cement paste. The objective of this paper was to study the cement paste microstructure, as a function of the water–cement ratio, in order to interpret the variations of the steel–mortar bond strength and the developing of the corrosion process in steel–mortar specimens kept in tap water and 3 percent sodium chloride solutions for 1 year. A description of the steel–mortar interface was also provided.

Details

Anti-Corrosion Methods and Materials, vol. 49 no. 1
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 1 June 1999

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

Keywords

Article
Publication date: 1 February 2001

M. Deyá, V.F. Vetere, R. Romagnoli and B. del Amo

The efficiency of two anticorrosive pigments containing aluminium polyphosphate was studied. Pigments were analysed by current analytical techniques and characterised by…

Abstract

The efficiency of two anticorrosive pigments containing aluminium polyphosphate was studied. Pigments were analysed by current analytical techniques and characterised by FT‐IR spectrometry. The anticorrosive properties of the selected pigments were evaluated following the electrochemical behaviour of a steel electrode in pigments suspensions. In a second stage, solvent‐borne paints with 30 and 10% v/v of the pigment and PVC/CPVC (pigment volume concentration/critical pigment volume concentration) ratio 0.8 were formulated. Three resins were chosen as film forming materials: an alkyd, an epoxy and a vinyl. The performance of the resulting anticorrosive paints was assessed by accelerated (salt spray cabinet and humidity chamber) and electrochemical tests (corrosion potential, ionic resistance and polarisation resistance). The anticorrosive performance of the tested paints was closely related with pigment composition. The nature of the resin was also of importance; in this sense, epoxy paints showed the best anticorrosive performance. Good correlation has been obtained between accelerated and electrochemical tests.

Details

Pigment & Resin Technology, vol. 30 no. 1
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 4 January 2013

O.R. Batic, J.D. Sota, J.L. Fernández, N. Bellotti and R. Romagnoli

This research aims to study the influence of limestone filler on rebar corrosion.

Abstract

Purpose

This research aims to study the influence of limestone filler on rebar corrosion.

Design/methodology/approach

Mortar samples containing 35% calcareous filler and with a rebar inserted in the axis, were cast. Specimens were cured at the open air and during 28 days in lime water. After curing, they were submerged in two electrolytes (tap water and 3% NaCl) and corrosion parameters (corrosion potential and corrosion current) were monitored over time by d.c. techniques. Simultaneously, electrochemical noise measurements were carried out. After corrosion tests, rebars were pulled out by lateral compression, and their surface observed by scanning electron microscopy.

Findings

In general, carbonate additions impaired mortar protective properties, especially in the presence of chloride and changed the nature of the protective layer on rebars. The curing process did not introduce significant differences except for mortars with a high water cement ratio cured in lime water for which the beneficial effects of the simultaneous presence of carbonate and lime in the pore solution could be appreciated. The role of carbonate additions is to provide carbonate anions to passivate rebars. This passivation process caused corrosion rates not to be so high. Carbonate anions also deposited on oxide spots which were rendered passive but this process was not uniform. Certain areas on the rebar underwent intense carbonation while others showed increased corrosion rates.

Originality/value

There are not many corrosion studies about the influence of limestone filler on rebars corrosion. Particularly, this paper deals with mortars containing high percentages of carbonate additions. Results showed that the presence of this type of admixture changes the structure of the passive layer and, sometimes, may increase corrosion rates.

Details

Anti-Corrosion Methods and Materials, vol. 60 no. 1
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 1 April 2000

G. Blustein, B. del Amo and R. Romagnoli

The objective of this work was to study the anticorrosive behaviour of three commercial pigments containing micronized zinc phosphate. The chemical analyses of the…

Abstract

The objective of this work was to study the anticorrosive behaviour of three commercial pigments containing micronized zinc phosphate. The chemical analyses of the pigments were carried out in the laboratory to characterise them with respect to their composition and soluble matter. It was proposed to check pigments’ efficiency in solvent‐borne paints with 30 per cent v/v of the pigment by volume and a pigment volume concentration/critical pigment volume concentration ratio (PVC/CPVC) equal to 0.8. The behaviour of paints formulated with two binders (alkyd and epoxy) was assessed by accelerated (salt spray cabinet, humidity chamber and accelerated weathering) and electrochemical (corrosion potential, ionic resistance and polarisation resistance) tests. It was demonstrated that pigment performance is highly influenced by their solubility which, in turn, could influence the formation of the protective layer on the metal substrate. Good correlation was obtained between salt spray and electrochemical tests.

Details

Pigment & Resin Technology, vol. 29 no. 2
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 18 August 2020

Oriana D'Alessandro, Christian Eduardo Byrne, Gonzalo Selmi and Cecilia Deyá

This paper aims to formulate and prepare a series of alkyd paints with new anticorrosive pigments, eco-friendly to the environment, based on a natural zeolitic rock…

Abstract

Purpose

This paper aims to formulate and prepare a series of alkyd paints with new anticorrosive pigments, eco-friendly to the environment, based on a natural zeolitic rock modified by ion exchange to incorporate passivating cations.

Design/methodology/approach

The electrochemical characterization of the painted steel was carried out by conductivity measurements, linear polarization tests, measurements of the corrosion potential and electrochemical noise measurements. Besides, accelerated tests in standard environmental chambers were also carried out.

Findings

The results show that clinoptilolite–mordenite-based pigments incorporated in the paint provide acceptable anticorrosive properties, taking into account their low environmental impact and the use of a natural resource of low cost. The inhibitory efficiency of ZLa is higher than 80% and of ZPr is close to 70%. The electrochemical assays of the coated panels with the alkyd paints ZLa and ZPr shows similar behavior.

Research limitations/implications

In this work, good results were obtained with an alkyd resin, but other resins could be tested. Paints could also be formulated with modified zeolites as a complement to others traditional anticorrosive pigments.

Practical implications

These paints could be used for the protection of metal structures in low corrosive environments.

Originality/value

There are not many published works using zeolites as anticorrosive pigments.

Details

Pigment & Resin Technology, vol. 50 no. 2
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 29 November 2018

Yingjun Zhang, Xue-Jun Cui, Yawei Shao, Yanqiu Wang, Guozhe Meng, Xiu-Zhou Lin, Dongquan Zhong and Dajian Wang

This paper aims to prepare a residual rust epoxy coating by adding different quantities of phytic acid (PA) on the surface of the rusty steel and investigate the corrosion…

Abstract

Purpose

This paper aims to prepare a residual rust epoxy coating by adding different quantities of phytic acid (PA) on the surface of the rusty steel and investigate the corrosion protection of PA and its action mechanisms.

Design/methodology/approach

A residual rust epoxy coating by adding different quantities of PA was prepared on the surface of the rusty steel. The influence of PA on the corrosion resistance of epoxy-coated rusty steel was investigated by means of electrochemical impedance spectroscopy and adhesion testing.

Findings

Results indicated that PA can substantially improve the corrosion resistance of epoxy-coated rusty steel. This improvement is due to the reaction of PA with residual rust and generation of new compounds with protection properties and increased adhesive strength effects on the coating/metal interface. The coating showed better protection performance when 2 per cent PA was added.

Originality/value

Considering the structure of the active groups, PA has strong chelating capability with many metal ions and can form stable complex compounds on the surface of a metal substrate, thereby improving corrosion resistance. In recent years, PA has been reported to be useful in the conversion of coatings or as green corrosion inhibitor. To the best of the authors’ knowledge, few studies have reported the use of PA as a rust converter or residual rust coating. The present work aims to improve the corrosion resistance of residual rust epoxy coating by adding PA.

Details

Anti-Corrosion Methods and Materials, vol. 66 no. 2
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 5 March 2018

Sofia Bogdan, Cecilia Deya, Oscar Micheloni, Natalia Bellotti and Roberto Romagnoli

This paper aims to study five vegetables extracts as possible additives to control bacterial growth on indoor waterborne paints. The extracts were obtained from the weeds…

Abstract

Purpose

This paper aims to study five vegetables extracts as possible additives to control bacterial growth on indoor waterborne paints. The extracts were obtained from the weeds Raphanus sativus, Rapistrum rugosum, Sinapis arvensis, Nicotiana longiflora and Dipsacus fullonum, used in traditional medicine as antimicrobial compounds.

Design/methodology/approach

Weeds extracts were characterized by Fourier transform infrared spectroscopy and UV–Vis spectrophotometry. Their antibacterial activity against Escherichia coli and Staphylococcus aureus was also determined. Afterward, selected extracts were incorporated in waterborne paint formulations. The paints’ antimicrobial activity was assessed against S. aureus, monitoring biofilm formation by environmental scanning electron microscopy.

Findings

As a general rule, results showed that tested paints were efficient in inhibiting biofilm formation, especially that formulated with Nicotiana longiflora.

Practical implications

The tested paints can be used to protect walls from microbial colonization, which shortened coatings’ useful life by discoloration and/or degradation. Concomitantly, indoor microbial colonization by aerosols could be also diminished. This is especially important in places that should have high standards of environmental hygiene, as in the food industry, health-care and sanitary centers.

Originality/value

The main value of this research was to study the antimicrobial activity of weeds extracts and to incorporate them in waterborne paints to diminish bacterial biofilm formation. This biofilm discolors and degrades the paint, and causes health problems. The use of natural compounds in coatings is increasing because of the convenience of using renewable sources, such as natural antimicrobials, in paint formulations.

Details

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

Keywords

Article
Publication date: 6 June 2016

Rachna Jain, Amit Sharma, Manish Kumar Bhadu and Keshave Swarnkar

The aim of this study was to evaluate the corrosion inhibition efficiency of steel samples in different environments before and after the treatment with rust metamorphose…

Abstract

Purpose

The aim of this study was to evaluate the corrosion inhibition efficiency of steel samples in different environments before and after the treatment with rust metamorphose (RM), which is formulated in this research study and shows excellent adherence over the rusted surface of substrate because of the presence of the P-O-Fe bond.

Design/methodology/approach

An RM solution (phosphorylated polyphenol) was synthesised and characterised using Fourier transform infrared spectroscopy (FT-IR), and then the degree of protection offered by it to steel surfaces with and without the treatment with the RM solution in different atmospheres was evaluated;. Before and after treating with the RM solution, the corroded steel samples were characterised using X-ray diffraction (XRD), FT-IR, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The study of the passive behaviours of the corroded steel samples and RM-treated steel samples was done in different simulated atmospheres.

Findings

This RM solution is phosphorylated polyphenol solution (proved by FT-IR), which acts as a corrosion inhibitor on corroded steel surfaces because of the formation of a passive and symmetric adherent layer of phosphorylated polyphenol–iron complex (confirmed by FT-IR, XRD, EDS, SEM and adhesion X test). The significant improvement in corrosion resistance in splash conditions of 3.5 per cent NaCl, tap water and 1.5 per cent Na2SO4 was found with the treatment of phosphorylated polyphenol-based RM.

Originality/value

The development of RM and its characterisation with performance evaluation in different atmospheres is a novel approach in this research.

Details

Anti-Corrosion Methods and Materials, vol. 63 no. 4
Type: Research Article
ISSN: 0003-5599

Keywords

Book part
Publication date: 18 November 2020

Joseph Crawford and Matthew Knox

The contemporary human resource management (HRM) sector is faced with continual leadership development challenges. Unethical behavior in leaders is not the norm, but it is…

Abstract

The contemporary human resource management (HRM) sector is faced with continual leadership development challenges. Unethical behavior in leaders is not the norm, but it is also not the exception. Human resource training and development focus significantly on better leadership but have largely failed to create more effective leaders. The result? Employee and follower wellbeing have not seen their best days. In this chapter, authentic relationships comprising authentic leaders and authentic followers are posited as a solution. The call is for more rigor in the theory underpinning leadership development programs, assurance of such programs, and embedding ethics into the core of what leadership developers do.

Details

Contemporary Global Issues in Human Resource Management
Type: Book
ISBN: 978-1-80043-393-9

Keywords

1 – 10 of 166