Micaceous Iron Oxide Pigments Research Articles

One-pot hydrothermal synthesis of micaceous iron oxide pigment from jarosite waste

In this study, jarosite waste was adopted as feed material for micaceous iron oxide (MIO) pigment preparation by a one-pot hydrothermal reaction. The formation of MIO started from jarosite decomposition into akaganeite (β-FeOOH) nanoparticles in alkali solution, which then recrystallized and transformed into MIO crystals under high temperature and OH− concentration. The influences of NaOH concentration and reaction temperature on MIO formation were investigated. It was found that MIO formed when NaOH concentration and reaction temperature were equal to or higher than 2 M and 180°C, respectively. With an increase of NaOH concentration or reaction temperature, the particle size of MIO increased, leading to darkened color of the product. Moreover, quality evaluation indicated that the synthesized MIO fulfilled the required characteristics of micaceous iron oxide pigments for paints and the international standard of ISO 10601-2007 MIO-A1.

The effect of MIO pigments on corrosion resistance and adhesion of synthetic rubber-based primer

In this research, the corrosion resistance and adhesion property of a synthetic rubber-based primer reinforced with different ratios of micaceous iron oxide (MIO) pigments were studied. Coatings were applied on carbon steel panels and also on steel pipes of 219.1 mm outer diameter. Scanning electron microscopy (SEM) was used to investigate the dispersion of MIO particles in the rubbery matrix. The anticorrosion performance of the coatings was studied, using electrochemical impedance spectroscopy (EIS) and salt spray tests. In addition, the adhesion of primers to carbon steel substrates was evaluated by pull-off test. In order to investigate the effect of MIO particles on the flexibility of the pigmented primers, a cupping test was conducted. The adhesion of cold-applied tape to the formulated primers was assessed by peel adhesion test using hanging mass method. The results indicated that adding 5, 10, and 15 wt% of MIO pigments into the primer improved corrosion resistance of the coatings. An increase in the MIO loading up to 10 wt%, improved the adhesion of the primer to both steel substrate and cold-applied tape.

Synthesis and Characterization of Micaceous Iron Oxide Pigment from Oily Cold Rolling Mill Sludge

Oily cold rolling mill (CRM) sludge is a kind of solid waste produced in production process of cold rolled strip In China, more than one hundred thousand tons of oily CRM sludge is produced each year. The oily CRM sludge contains lots of valuable iron and alloying elements, along with plenty of hazardous organic components, which makes it an attractive secondary resource and an environmental contaminant at the same time At present, oily CRM sludge is mainly used as smelting raw materials Its direct re-use in sintering may lead to some problems because high oil content of oily CRM sludge results in increased emission of volatile organic compounds including dioxins and can lead to problems in waste gas purification systems, e.g glow fires in electrostatic precipitators. In this paper, micaceous iron oxide (MIO) pigment was synthesized from oily CRM sludge by means of the multi-step processes, including acid leaching, preparation of the ferric hydroxide precursor and hydrothermal synthesis. The experimental conditions, including NaOH concentration and hydrothermal reaction temperature were investigated in order to determine the optimal ones. The morphology and particle size of as-prepared MIO pigment were characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results showed that the obtained pigment had high purity (∼98.7%) and good oil absorption (∼18.8%). The synthesized MIO pigments met the required characteristics of MIO pigments for paints (ISO10601-2007). MIO pigments synthesis method presents a viable alternative for oily CRM sludge recycling.

New technology for recyclingmaterials from oily cold rollingmill sludge

Oily cold rolling mill (CRM) sludge is one of metallurgical industry solid wastes. The recycle of these wastes can not only protect the environment but also permit their reutilization. In this research, a new process of “hydrometallurgical treatment + hydrothermal synthesis” was investigated for the combined recovery of iron and organic materials from oily CRM sludge. Hydrometallurgical treatment, mainly including acid leaching, centrifugal separation, neutralization reaction, oxidizing, and preparation of hydrothermal reaction precursor, was first utilized for processing the sludge. Then, micaceous iron oxide (MIO) pigment powders were prepared through hydrothermal reaction of the obtained precursor in alkaline media. The separated organic materials can be used for fuel or chemical feedstock. The quality of the prepared MIO pigments is in accordance with the standards of MIO pigments for paints (ISO 10601-2007). This clean, effective, and economical technology offers a new way to recycle oily CRM sludge.

Investigation of corrosion protection afforded by inorganic anticorrosive coatings comprising micaceous iron oxide and zinc dust

The present study deals with the investigation of the effects of partial replacement of sacrificial zinc dust by high efficiency barrier micaceous iron oxide (MIO) pigments on the corrosion protection behaviour of inorganic zinc rich coatings. To this end, waterborne zinc rich silicate paints based on nanosilica modified potassium silicate were formulated with different contents of zinc and MIO. After being applied on carbon steel panels, the coatings were evaluated by electrochemical impedance spectroscopy, corrosion potential measurements and salt spray test. Replacement of zinc by MIO in the formulation of zinc rich paints was revealed to shorten the duration of cathodic protection stage while on the other hand giving satisfactory results in 1000 h of salt spray test. It was concluded that the incorporation of MIO pigments in conjunction with zinc into the formulation of inorganic zinc rich coatings is a potential means to control the reactivity and the barrier protection stage.

Evaluation of cathodic protection behavior of waterborne inorganic zinc‐rich silicates containing various contents of MIO pigments

PurposeThe aim of this paper is to study the corrosion protection behavior of water‐borne inorganic zinc‐rich coatings based on potassium silicate/nanosilica developed with various zinc and micaceous iron oxide (MIO) contents during cathodic protection stage.Design/methodology/approachThe formulated coatings were applied on carbon steel panels and were subjected to electrochemical impedance spectroscopy (EIS) and free corrosion potential measurements for characterization of corrosion protection behavior. Also atomic force microscopy (AFM) and optical microscopy were used to investigate the surface topography of coatings.FindingsAll of the coatings preserved the cathodic protection ability throughout 75 days of exposure to 3.5% NaCl solution. Supporting results of electrochemical tests and microscopic observations revealed that replacement of zinc by MIO particles reduced both the rate of reactivity and the duration of cathodic protection of inorganic zinc‐rich coatings. It was observed that the coatings demonstrated a reactivation step after a dry‐wet cycle implying that cyclic immersion can change the overall duration of cathodic protection stage.Originality/valueThe paper describes formulation and investigation of corrosion protection behavior of an environmentally friendly zero‐VOC coating as well as providing an insight into EIS of zinc‐rich coatings.

Micaceous iron oxide prepared from pyrite cinders by hydrothermal method

Micaceous iron oxide (MIO) with a hexagonal flaky shape was prepared by hydrothermal method. The ferric hydroxide used as precursor was obtained by an acidic leaching solution of pyrite cinders reacting with ammonia solution. The optimal experimental conditions for preparing micaceous iron oxide were investigated by orthogonal experiments. Micaceous iron oxide can be successfully prepared when optimal parameters of total iron concentration of 2.0 mol/L, pH value of 8, n(Fe2+)/n(Fe3+) of 0.1, mass of seed crystal of 1 g, reaction temperature of 260 °C and reaction time of 30 min are applied. X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffractometry (SAEM) were adopted to characterize the hydrothermal products prepared under optimal conditions. The results indicate that highly crystallized α-Fe2O3 hexagonal flakes, about 1.0–1.5 μm in diameter and 0.1 μm in thickness, are prepared. Furthermore, the quality of micaceous iron oxide prepared can meet the required characteristics of micaceous iron oxide pigments for paints (ISO10601—2007).

Evaluation of the corrosion resistance of an epoxy-polyamide coating containing different ratios of micaceous iron oxide/Al pigments

The corrosion resistance of an epoxy coating reinforced with different ratios of MIO/Al pigments was studied. The coatings properties were investigated by an electrochemical impedance spectroscopy (EIS), salt spray test, cathodic disbonding and a scanning electron microscope (SEM). The corrosion resistance of the epoxy coating was improved using MIO (micaceous iron oxide) and Al pigments. The corrosion resistance of the purely Al pigmented coating was considerably greater than the purely MIO pigmented coating. The cathodic disbonded area of coating was decreased using MIO and Al pigments. The decrease in disbonded area was more pronounced in the presence of Al particles.

Preparation of monodispersed micaceous iron oxide pigment from pyrite cinders

In this study, pyrite cinders are used as a second raw material for preparing micaceous iron oxide (MIO) pigment by leaching, precipitation and hydrothermal treatment. The optimal conditions for MIO synthesis, such as NaOH concentration, total iron concentration, reaction temperature and reaction time are investigated and discussed carefully, using pigment color and morphology as the major evaluation parameters. In addition, the synthesized products have been characterized by means of XRD and SEM/EDS. Under optimum conditions, the obtained MIO is uniform flake, metallic gray, and its mean particle size and aspect ratio are ~7.0μm and ~7.0. A scale-up experiment demonstrates its reproducibility. Besides, all the resulting products fulfill ISO 10601-2007, the standards of micaceous iron oxide pigments for paints.

Effect of PVC on the diffusion behaviour of water through alkyd coatings

The diffusion behaviour of water through alkyd coatings with micaceous iron oxide pigment at different pigment volume concentration (PVC) was studied by EIS and SEM techniques. The diffusion coefficients of water through the coatings were also calculated. The experimental results showed that, in the initial diffusion period, the diffusion processes of water through alkyd coatings immersed in 0.5 M NaCl followed the Fick's second law. Within the PVC values which have been studied, the diffusion coefficients of water diffusing through alkyd coatings initially decreased with increasing PVC, reaching a minimum value at 60%, and then increased with increasing PVC. When PVC was less than 60%, the barrier property of pigment was the main factor affecting the water diffusion behaviour. However, the coatings' microstructure played an important role when PVC was greater than 60%.

Effect of PVC on the Diffusing Behavior of Water through Alkyd Coatings

The diffusion behaviour of water through alkyd coatings with micaceous iron oxide pigment at different pigment volume concentration (PVC) was studied by EIS and SEM techniques. The diffusion coefficients of water through the coatings were also calculated. The experimental results showed that, in the initial diffusion period, the diffusion processes of water through alkyd coatings immersed in 0.5 M NaCl followed the Fick's second law. Within the PVC values which have been studied, the diffusion coefficients of water diffusing through alkyd coatings initially decreased with increasing PVC, reaching a minimum value at 60%, and then increased with increasing PVC. When PVC was less than 60%, the barrier property of pigment was the main factor affecting the water diffusion behaviour. However, the coatings' microstructure played an important role when PVC was greater than 60%. (C) 2002 Elsevier Science Ltd. All rights reserved.

Properties of Austrian micaceous iron oxide

Micaceous iron oxide pigments have been used successfully for many years in undercoating and finishing paints where a high level of protection is demanded and an impervious coating required.