Zinc Pigments Research Articles

Degradation behavior of zinc-rich epoxy coatings in simulated marine tidal zone

Degradation behaviors of zinc-rich epoxy coatings (ZRCs) were investigated using a simulated tidal apparatus. The steel substrate can be cathodically protected effectively in both immersion and tidal zones. The tidal level has a remarkable influence on the activation rate of zinc pigments in the ZRCs. Both activation degree and consumption of the zinc pigments in the ZRCs decreases with the rise of tidal level. More durable protection offered by zinc pigments can be achieved at the higher tidal level. The encapsulation of corrosion products hinders the sacrifice of zinc pigments, resulting in the high residual of metallic Zn even after the disability of effective cathodic protection of the ZRCs. Moreover, the tidal level affects the phase composition of corrosion products. In addition to the dominant phases including ZnO and Zn5OH8Cl2, Zn5CO32OH6 and Zn4OH6SO4 are formed in outer layers of the ZRCs at the relatively high tidal level.

A Multi-Analytical Approach for the Characterization of Painting Materials and Metal Soap Formation in Two Artworks by the Argentinian Painter Antonio Berni

This work describes the characterization of pigments and ground layers in two paintings by the renowned Argentinian painter Antonio Berni (1905–1981). The studied paintings are “Toledo” and “Figure” from the collection of the Provincial Museum of Fine Arts in Santa Fe (Argentina). To approach this goal, an integrated investigation comprising in situ X-ray fluorescence measurements by means of a portable system (pXRF), micro-Raman spectroscopy, Attenuated Total Reflection–Fourier transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS) was carried out. The results revealed a chromatic palette with inorganic pigments, such as ultramarine blue, cobalt blue, lead white, zinc white, yellow cadmium, and hydrated chromium oxide (viridian), together with a preparation layer consisting of a mixture of earth, lead white, and calcite in “Toledo”. On the other hand, the preparation layer in “Figure” was characterized as lithopone, a mixture of barium sulfate and zinc sulfide. ATR-FTIR-analysis revealed the formation of metallic soaps in both paintings due to the reaction of fatty acids from a drying oil used as a binder with lead and zinc pigments, as confirmed by comparison with the infrared spectra of synthetic lead and zinc soaps. This study contributes to the understanding of Berni’s painting style and the future restoration of both artworks.

Study on fabricating epoxy coatings reinforced with iron oxide flakes and nano silica

Flake micaceous iron oxide (MIO) pigment is a natural flake pigment, together with nano silica (NS) used to increase mechanical properties and corrosion resistance of coatings based on epoxy resin Epotec YD011X75 cured with Domide G5022. MIO and NS were dispersed into epoxy resin Epotec YD011X75 by mechanical stirring combined with ultrasonic vibration. The structural morphology of the materials was characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and Transmission Electron Microscopy (TEM). Functional groups in epoxy/curing agent/MIO polymers analyzed using Fourier Transform Infrared Spectroscopy (FTIR). The thermal property of the material is evaluated by Thermogravimetric and Differential Scanning Calorimetry (TG-DSC). Epoxy coatings with flake micaceous oxide iron, nano silica, phosphate zinc pigment (P), talc filler powder (T), additives, and solvents are prepared by grinding and mechanical stirring. The mechanical properties of epoxy coatings were evaluated by standards for epoxy coatings. The anti-corrosion properties of the coatings on steel were evaluated by the salt fog spray method and electrochemical method. The research results have fabricated two formulations of epoxy coatings based on epoxy resin Epotec YD011X75 with the most appropriate mass ratio of YD011X75/(MIO/P/T) is 40/60 (wt/wt); of which one does not have nano silica (epoxy coating MIO2); one with 1 wt% nano silica (epoxy coating MIO5). The thermal stability of epoxy coating MIO5 is better than epoxy coating MIO2. The decomposition temperature of 50 wt% of epoxy coatings MIO5 and MIO2 is 528.34°C and 470.53°C. The formed epoxy coatings achieve the physical chemistry properties, mechanical properties, and corrosion resistance properties of steel for epoxy coatings, in which the epoxy coating MIO5 is better than the epoxy coating MIO2.

Flake-like ZnAl alloy powder modified waterborne epoxy coatings with enhanced corrosion resistance

Zinc-rich epoxy coatings (ZRECs) have been widely used to protect steel against corrosion because of their excellent corrosion resistance. However, the ZRECs preparation usually used a large amount of Zn powders and organic solvents, which not only wasted resources but also produced a great quantity of volatile organic compounds (VOC). Therefore, it was necessary to develop a method which can prepare epoxy coatings with low Zn content, great corrosion resistance and green environmental protection. In this paper, three different flake metal powders (Zn, ZnAl alloy and ZnAlMg alloy) were used to replace spherical Zn powders to develop environmentally friendly coatings with low pigment content. The coatings were evaluated by salt spray test and electrochemical test. The results show that the use of flake metal powders instead of spherical zinc pigments can enhance the electrical connection between metal particles, prolong the path of corrosive medium infiltration into the coatings, enhance the physical shielding effect of the coatings, and reduce the pigment content by one third. Among them, the ZnAl coatings displayed the best anti-corrosion performance resisting salt fog corrosion for 28 days. In addition, the experimental results show that the self-healing ability of the coatings also plays an important role in the immersion middle and late stages. In short, the waterborne epoxy ZnAl coatings are suitable for large-scale application in harsh environments.

Immediate and Sustained Effects of Cobalt and Zinc-Containing Pigments on Macrophages.

Pigments are among the oldest nanoparticulate products known to mankind, and their use in tattoos is also very old. Nowadays, 25% of American people aged 18 to 50 are tattooed, which poses the question of the delayed effects of tattoos. In this article, we investigated three cobalt [Pigment Violet 14 (purple color)] or cobalt alloy pigments [Pigment Blue 28 (blue color), Pigment Green 14 (green color)], and one zinc pigment [Pigment White 4 (white color)] which constitute a wide range of colors found in tattoos. These pigments contain microparticles and a significant proportion of submicroparticles or nanoparticles (in either aggregate or free form). Because of the key role of macrophages in the scavenging of particulate materials, we tested the effects of cobalt- and zinc-based pigments on the J774A.1 macrophage cell line. In order to detect delayed effects, we compared two exposure schemes: acute exposure for 24 hours and an exposure for 24 hours followed by a 3-day post-exposure recovery period. The conjunction of these two schemes allowed for the investigation of the delayed or sustained effects of pigments. All pigments induced functional effects on macrophages, most of which were pigment-dependent. For example, Pigment Green 19, Pigment Blue 28, and Pigment White 4 showed a delayed alteration of the phagocytic capacity of cells. Moreover, all the pigments tested induced a slight but significant increase in tumor necrosis factor secretion. This effect, however, was transitory. Conversely, only Pigment Blue 28 induced both a short and sustained increase in interleukin 6 secretion. Results showed that in response to bacterial stimuli (LPS), the secretion of tumor necrosis factor and interleukin 6 declined after exposure to pigments followed by a recovery period. For chemoattractant cytokines (MCP-1 or MIP-1α), delayed effects were observed with a secretion decreased in presence of Pigment Blue 28 and Pigment violet 14, both with or without LPS stimuli. The pigments also induced persisting changes in some important macrophage membrane markers such as CD11b, an integrin contributing to cell adhesion and immunological tolerance. In conclusion, the pigments induced functional disorders in macrophages, which, in some cases, persist long after exposure, even at non-toxic doses.

Assessment of durability and zinc activity of zinc-rich primer coatings by electrochemical noise technique

The three-coat system consisting of a zinc-rich primer, epoxy midcoat, and polyurethane topcoat has been widely adopted for corrosion protection of structural steel bridges. Corrosion mitigation is afforded by the barrier characteristics of the various layers as well as beneficial galvanic coupling of the zinc pigments in the primer to the steel substrate when subjected to corrosive environments such as with moisture ingress and coating defects. The dispersed zinc pigments in the binder require adequate electronic coupling in order to provide the beneficial electrochemical coupling of the zinc to the steel. The application of the electrochemical noise (EN) technique to identify coating corrosion performance was reviewed in controlled laboratory tests. Zinc pigment activation and transition to passive-like conditions in defect and defect-free coating specimens could be identified by EN. The characteristic charge of noise events resolved by shot noise analysis was demonstrated to be related to anodic polarization of extended active zinc pigments adjacent to coating defect sites galvanically coupled to the exposed steel and passivated zinc pigments. Electrochemical noise resistance was shown to convey zinc/steel interfacial behavior in cases with sufficient activity but largely reflects coating barrier quality for intact coatings.

Evaluation of coating performance on carbon steel A-36 in copper concentrate environment using electrochemical impedance spectroscopy

The presence of chalcopyrite increases the corrosion rate of carbon steel through a galvanic couple. In this study, five organic coating systems were evaluated for their strength against consequent corrosion in the presence of copper concentrate by electrochemistry impedance spectroscopy (EIS) measurement. The coating system studied are a single application epoxy coating (C1); a three-layer epoxy system with zinc-rich epoxy primer base coat, surface tolerant epoxy middle layer, and a top layer polyurethane (C2); a three-layer epoxy system that has the advantages of fast dry time consist of epoxy zinc phosphate base coat primer, the middle layer of the epoxy primer containing the pigment zinc phosphate and top layer polyurethane (C3); metallic pigmented polyurethane coating (C4), and an epoxy coating which can be applied to wet surfaces or in water (C5). All those systems have been tested by the EIS. The test results showed that C2, C3, C4, and C5 coating systems maintained good barrier properties during the immersion process, the low frequency |Z| is more than 108Ω.cm2 after 30 days of immersion exposure. Epoxy modified coating (C1) had the lowest impedance with resistance under 106 Ω.cm2 provide poor corrosion protection.

Impressed current cathodic protection (ICCP) of mild steel in association with zinc based paint coating

In this study, an epoxy ester resin-based paint formulation incorporating spherical zinc as a pigment with a size range of 1–2 µm is investigated for usage in conjunction with impressed current cathodic protection, and the results are presented. Painted mild steel containing spherical zinc PVC = 61% exhibits negligible iron loss ∼ 0.48 ppm when used under impressed current condition.Electrochemical corrosion of mild steel is significantly reduced.This can be attributed to the combined effect of sacrificial protection by zinc pigments and supply of electrons by the impressed current system. Lower protection potential will be required when mild steel is painted by a coating containing spherical zinc PVC = 61% under impressed current application.

Concepts of steel protection by coatings with a reduced content of zinc pigments

In zinc-rich primers Zn acts in the initial stage as sacrificial anode (cathodic protection). During lifetime Zn is transformed into its corrosion products, which seal the coating's pores (barrier protection). Such coatings are typically very highly pigmented which could cause the deterioration of cohesion and/or adhesion as well as mechanical properties. The formulations of different Zn pigments in epoxy matrices were developed with concentration of zinc particles reduced to about 50 wt% in the dry coatings. As Zn pigments were used: mixtures of zinc pigments with different particle size and particle shape (dust, flakes), zinc dust with organic surface treatment, zinc alloy pigments – ZnMg and ZnSn as well as Zn dust with an addition of graphene or carbon nanotubes.The mechanisms of protection by coatings with a reduced content of zinc pigments were studied in comparison with that of commercial zinc rich primers – epoxy and ethyl silicate – by the following methods: Scanning Kelvin Probe (SKP) detection of artificially inflicted samples after impact of salt spray test (SST), polarization experiments and EOC detections in combination with different corrosive impact, as well as by SST and the exposure to the natural marine environment (sea water splash zone).It was found that cathodic protection is shown by primer pigmented with Zn flakes, with zinc phosphate and barium sulphate addition as well as by primer containing Zn dust and graphene. They reach an open circuit potential (EOC) significantly below −0.86 V. Primers pigmented with ZnSn or Zn dust with an addition of carbon nanotubes (CNT) keep their EOC in the transition phase between −0.7 V and −0.86 V. Other primers with a reduced content of zinc pigments show only barrier protection.Coatings characterized by EOC in the range of cathodic protection or in the transition phase have very good protective properties in the corrosive environment. However, good anticorrosive properties were found also in the case of primers which do not show any cathodic protection, such as the primer pigmented with a mixture of Zn particles with different size and the primer containing Zn dust with chemical surface treatment. This shows that good anticorrosive properties can be obtained even if cathodic protection is not observed.

Low-Temperature Synthesis of Electrically-Conductive Pigment Zinc Oxide Doped with Gallium Donor

Low-Temperature Synthesis of Electrically-Conductive Pigment Zinc Oxide Doped with Gallium Donor

Formation of zinc oxalate from zinc white in various oil binding media: the influence of atmospheric carbon dioxide by reaction with 13CO2

The formation of metal oxalates in paintings has recently gained a great deal of interest within the field of heritage science as several types of oxalate compounds have been identified in oil paintings. The present work investigates the formation of metal oxalates in linseed oil in the presence of the artists’ pigments zinc white, calcite, lead white, zinc yellow, chrome yellow, cadmium yellow, cobalt violet, and verdigris. The oil paint films were artificially photo-aged by exposure to UVA light at low and high relative humidity, and afterwards analysed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The results showed that, compared to the other pigments investigated, zinc white is especially prone to metal oxalate formation and that high humidity is a crucial factor in this process. Consequently, the reactivity and photo-aging of ZnO in various oil binding media was investigated further under simulated solar radiation and at high relative humidity levels. ATR-FTIR showed that zinc oxalate is formed in all oil binding media while X-ray powder diffraction (PXRD) revealed it was mainly present in an amorphous state. To examine whether atmospheric CO2(g) has any influence on the formation of zinc oxalate, experiments with isotopically enriched 13CO2(g) were performed. Based on ATR-FTIR measurements, neither Zn13C2O4 nor Zn13CO3 were formed which suggests that the carbon source for the oxalate formation is most likely the paint itself (and its oil component) and not the surrounding atmosphere.

X-ray Nanospectroscopy Reveals Binary Defect Populations in Sub-micrometric ZnO Crystallites

Besides its many applications in electronics, photonics, and catalysis, ZnO has also been extensively used as the pigment zinc white ever since its introduction in the first half of the 19th century. It is shown here that zinc whites (ZnO formed through zinc vapor oxidation) form a chemically binary system, with each of the sub-micrometric crystallites belonging to either of two distinct classes. The observation of the two classes is done based on X-ray absorption nanospectroscopy and was determined to be caused by differences in the populations of anisotropic crystal defects. A theoretical assessment of the vapor oxidation synthesis method is formulated that predicts that the binary distinction in crystal defect populations is caused by local variations in synthesis parameters. As the crystal defect population in ZnO has been shown to be related to its catalytic properties, these results provide fundamental insights on the link between the intrinsic properties of zinc white and its degradation issues in oil paint.

In-situ technical study of modern paintings - Part 2: Imaging and spectroscopic analysis of zinc white in paintings from 1889 to 1940 by Alessandro Milesi (1856-1945).

We present a multi-analytical in situ non-invasive study of a series of emblematic paintings by Alessandro Milesi (1856-1945) from the collection of the International Gallery of Modern Art Ca' Pesaro in Venice. Eight paintings dated from 1897 to 1910 were studied with imaging and spectroscopic techniques. White pigments were characterized by a combination of X-ray fluorescence spectroscopy which traced the presence of zinc-based pigments in Milesi's paintings, Raman Spectroscopy, Laser Induced Fluorescence (LIF) Spectroscopy and Time-resolved Luminescence Imaging. Time-resolved analysis of luminescence emissions revealed the nanosecond emission from organic compounds and the slower emission from the luminescent inorganic pigment Zinc Oxide that varied between 1.1 and 1.6 microseconds. In this work, data regarding the distribution of luminescent pigments was acquired with a time-gated imaging detector. Furthermore, differences in emission decay kinetics recorded from different paintings can be ascribed to different paint formulations or origins of the Zinc white in paint.

Phosphorous-based epoxy resin composition as an effective anticorrosive coating for steel

Epoxy resin (ER) is an attractive material for metal protection against corrosion; it can form a strongly adhered film onto a metal surface through its multi coordination sites. In this study, an epoxy resin-based formulation was designed, prepared, and applied onto steel surface with and without a pigment. The anticorrosive formulation (ER–MDA–ZP) was prepared from the ER and the hardener 4,4′-methylene dianiline (MDA) in the presence of the anticorrosive pigment zinc phosphate (ZP). A second standard formulation (ER–MDA) was prepared without ZP. The epoxy and the hardener react to form a 3D cross-linked polymeric network with multicoordination sites (hydroxyl and amino groups) for metals. The characterization of the epoxy resin was performed using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H and 31P NMR). Both samples exhibited excellent thermal properties as they subjected to thermal analysis using differential scanning calorimetry. The ER–MDA–ZP formulation showed a higher glass transition temperature (Tg) than ER–MDA. The coated steel specimens were immersed for 1 h in a 3 wt% NaCl solution and their anticorrosive properties were monitored by electrochemical impedance spectroscopy (EIS). The total resistance (Rt) values obtained by the EIS method for the ER–MDA and ER–MDA–ZP formulations were 21,383 Ω cm2 and 55,143 Ω cm2, respectively. The coated steel samples after the acid treatment were subjected to aging by exposing them to a UV light for 2000 h. The aging caused the Rt values to drop to 1621 Ω cm2 and 7264 Ω cm2, respectively. The results indicate the formation of a highly stable film of ER–MDA–ZP formulation on the steel surface that withstands an accelerated corrosive environment of 2000 h exposure to UV light and 1 h of immersion in a 3 wt% NaCl.

Anticorrosive Performance of New Epoxy-Amine Coatings Based on Zinc Phosphate Tetrahydrate as a Nontoxic Pigment for Carbon Steel in NaCl Medium

Epoxy resin is known to react with a hardener such as polyamine to form a thermoset 3D polymer net with an outstanding physical and mechanical properties. They are widely used in coating and adhesives. In this study, we present a new epoxy resin material useful for making an anticorrosive formulation for carbon steel. The epoxy resin presented in this study is diglycidyl ether 4, $$4^{\prime }$$ -dihydroxy diphenyl sulfone (DGEDDS). It was prepared in a two-step process that involves reacting epichlorohydrin with 4, $$4^{\prime }$$ dihydroxy diphenyl sulfone then with sodium hydroxide. The structural elucidation of DGEDDS was carried out with Fourier transform infrared. The anticorrosive formulation DGEDDS–MDA–ZPH was prepared from DGEDDS and the hardener 4, $$4^{\prime }$$ -methylene dianiline (MDA) in the presence of the anticorrosion pigment zinc phosphate tetrahydrate (ZPH). Another standard formulation (DGEDDS–MDA) was prepared without ZPH. The physicochemical and anticorrosive performance of the coated carbon steel was evaluated using electrochemical impedance spectroscopy (EIS). The coated surface was subjected to morphological characterization by SEM before and after immersion in the corrosive medium and exposing it to the UV radiation. The value of the polarization resistance ( $$R_{\mathrm{p}}$$ ) obtained by the EIS method for the standard coating DGEDDS–MDA and epoxy composite coating DGEDDS–MDA–ZPH was 31898 and 72611 $$\Omega \,\hbox {cm}^{2}$$ during the 1 h of immersion in 3 wt% NaCl, respectively. After aging by exposing the coatings for a 2000 h to UV radiation the values were dropped to 2596 and 5189 $$\Omega \,\hbox {cm}^{2}$$ , respectively. The values show the high stability and resistance of the epoxy resin coating to electrolytes and UV radiation. The coating even showed higher stability in the presence of ZPH pigment. As shown in the results, the tricomponent composite showed an outstanding stability in protecting carbon steel form corrosion in an aggressive marine environment where UV is very intense and the humidity and salts are very high.

Corrosion behavior of organic epoxy-xinc coating with fly ash as an extender pigment

The utilization of industrial waste like fly ash may reduce the environmental risk. The properties of fly ash are useful and may contribute in organic coating field. This paper study the new strategy for coating with enhanced cathodic and barrier protection simultaneously. The aim of this study is to show that the low pigment volume concentration (PVC) of the coating may have a great protection by introducing a small amount of fly ash as an extender pigment into the coating material. Specifically, we compare the protection offered by epoxy coating with 10% of PVC. The zinc pigment in the coating was replaced with fly ash at 10, 20, 30 and 40 vol/vol %. The replacing of fly ash in the formulation reduced the pigments percentage in the coating. Polarization test was conducted up to 30 days. The corrosion behaviors of the coated specimens were observed, and the corrosion rates were calculated based on the corrosion kinetics obtained from the test. The results demonstrated that addition of fly ash into the coating material, galvanizing the coated specimen, thus proved that fly ash has cathodic properties. The addition of fly ash changes the mechanism of protection from barrier protection mainly came from epoxy resin to cathodic protection from fly ash.

Time-Resolved Photoluminescence Microscopy for the Analysis of Semiconductor-Based Paint Layers.

In conservation, science semiconductors occur as the constituent matter of the so-called semiconductor pigments, produced following the Industrial Revolution and extensively used by modern painters. With recent research highlighting the occurrence of various degradation phenomena in semiconductor paints, it is clear that their detection by conventional optical fluorescence imaging and microscopy is limited by the complexity of historical painting materials. Here, we illustrate and prove the capabilities of time-resolved photoluminescence (TRPL) microscopy, equipped with both spectral and lifetime sensitivity at timescales ranging from nanoseconds to hundreds of microseconds, for the analysis of cross-sections of paint layers made of luminescent semiconductor pigments. The method is sensitive to heterogeneities within micro-samples and provides valuable information for the interpretation of the nature of the emissions in samples. A case study is presented on micro samples from a painting by Henri Matisse and serves to demonstrate how TRPL can be used to identify the semiconductor pigments zinc white and cadmium yellow, and to inform future investigations of the degradation of a cadmium yellow paint.

The anti-corrosion performance of water-borne paints in long term tests

Abstract One of the most inexpensive and effective method to protect steel against corrosion is paints containing active pigments. The traditional way to test these coatings performance is by accelerated tests (exposition to salt spray and/or humidity chambers) and electrochemical tests (corrosion potential, ionic resistance and electrochemical impedance spectroscopy). However, these tests give incomplete information if the results are not correlated to outdoor or service tests. The aim of this work was to evaluate water-borne epoxy anticorrosion paints containing different commercial phosphate pigments. The paints were exposed to a semi-industrial atmosphere for 7 years. Electrochemical tests and accelerated assays were also done in order to find a correlation between laboratory and service tests. The results obtained showed no correlation between those from pigment suspensions and those from painted panels, as it seemed that paint performance is highly dependent on the resin. The pigments zinc iron phosphate and zinc aluminium phosphate performed poorly in pigment suspensions. However, the coatings containing them exhibited the highest ionic resistance, the lowest film capacitance and gave the better results in outdoor tests. Results in outdoor exposure tests correlated with those from impedance measurements.

Single crystal X-ray structure of the artists' pigment zinc yellow

The artists' pigment zinc yellow is in general described as a complex potassium zinc chromate with the empirical formula 4ZnCrO4·K2O·3H2O. Even though the pigment has been in use since the second half of the 19th century also in large-scale industrial applications, the exact structure had hitherto been unknown. In this work, zinc yellow was synthesised by precipitation from an aqueous solution of zinc nitrate and potassium chromate under both neutral and basic conditions, and the products were compared with the pigment used in industrial paints. Analyses by Raman microscopy (MRS), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and powder X-ray diffraction (PXRD), showed that the synthesised products and the industrial pigment were identical. Single-crystal X-ray crystallography determined the structure of zinc yellow as KZn2(CrO4)2(H2O)(OH) or as KZn2(CrO4)2(H3O2) emphasizing the μ-H3O2− moiety. Notably, the zinc yellow is isostructural to the recently structurally characterized cadmium analog and both belong to the natrochalcite structure type.

Переработка цинксодержащих пылей медеплавильного производства на цинковые пигменты

Переработка цинксодержащих пылей медеплавильного производства на цинковые пигменты