What are Iron Oxide Pigments

Iron oxide pigments are extensively used in diverse industries for their color stability, durability and resilience. These pigments have their own plethora of shades including, yellows, browns, reds and blacks, making them adaptable for applications like construction materials, cosmetics, plastics and coatings. The process of manufacturing iron oxide pigments involves different key stages that ensure consistent performance and quality. In this article, we will take a sneak peak how iron oxide pigments are manufactured, focusing on the various techniques and methods involved.

Terminologies

In the world of iron oxide pigments, nomenclatures can be practiced as an elementary thing based on the color formation. It is seen that some of the natural colors have nomenclatures that normally reflect the geographies where they initially procured.

In case of synthetic oxides, the industries experience that it is more than enough to talk about the plethora of respective pigment colors ranging within black, brown and yellow.

Most of the synthetic pigments can be differentiated according to the way they are made to their final formation. On the other hand, if we go by the investigation Bureau of this respective industry, they have bifurcated the synthetic reds into a unique nomenclature, which is an oxide derived by scorching of iron sulphate (in other terms as copperas).

In terms of natural oxides, a plethora of nomenclatures has been brought to terms to materials derived from discrete sources. An effective sample case is that of Spanish red, emanated from the organic red of certain attributes from Spain. A wide variety of natural oxides having unique names are no longer bounded by the same; and are of only spasmodic significance. Therefore, the respective nomenclatures are enough to define contemporary oxide products such as-Vandyke brown, ocher, umber, sienna, brown and black.

A kaleidoscope through time: Iron Oxide Pigments

If we have a look in the late nineteenth century, these pigments were collected and derived wholly from natural resources, generally with minimal tweakings other than physical ablution. In some scenarios, roasting or scorching was also implemented. However, in the first phase of the twentieth century, chemical methodologies were cultured for synthetic fabrication of profit-oriented oxides. This methodology offered enhanced constancy as well as attributes not attainable with natural oxides, and inevitably synthetics overrides natural substances for different applications.

Fast forward to current era, the iron oxide pigment industry generates a blend of synthetic oxides furnished with a range of parameters, appended with a variety of natural oxides coveted because of their affordability or uniqueness of color.

This industrial realm is mellow, with products keeping up with commercial uses according to materialistic and chemical attributes, formidable among which are nontoxicity and solidity. Due to the abundance and inexpensiveness, iron oxide is responsible for one of the greatest fraternities of colored inorganic pigments. This industry experiences that synthetic pigments, often derived from scrap or as a byproduct of other businesses, are now the greater part of the iron oxide industry.

Let’s go through the current production methodologies of iron oxide pigments

• The Laux methodology: This process was originally used exclusively to produce aniline (C6H5NH2) from nitrobenzene (C6H5NO2). It was not until 1925 that a renowned chemist- Dr. Laux founded that, under certain chemical state, the iron oxide produced in this reaction could be used as an immensely color-strength iron oxide pigment. The methodology is mainly used to produce black iron oxide using cast iron chips, although it is also possible to react it to create iron oxide yellow. In this case, the feigned granules are utilized, irrespective of the presence of cast-iron chips. Another interesting science in these iron oxide pigment manufacturing is that red iron oxide pigment can yield from black iron oxide in a further thermal yet energy-efficient reaction step. The Laux process is the greatest sustainable production process for iron oxide pigments, of all time, since huge quantities of ferrous scrap are used as raw materials.


• The Peniman process: In this process, iron scrap is oxidized to yellow iron oxide in a sulfuric acid medium under the action of atmospheric oxygen. In this methodology, ferrous sulphate acts as a catalyst. As a matter of fact, in order to come up with high-end yellow pigments, the existence of yellow nuclei is also important.


• The precipitation process: In this methodology, to achieve yellow iron oxide pigment, one needs to oxidize iron sulfate in an alkaline environment in the presence of atmospheric oxygen.


• Synthetic Methodology: The Calcination Process: This methodology is an alternative approach used to produce iron oxide pigments, particularly red pigments. This process involves heating iron salts at high temperatures to commence thermal decomposition. The crucial steps are-


• Raw material arrangement- An iron compound along with ferric oxide is treated in a furnace at temperatures varying within 600 to 1000 degrees celcius.


• Thermal Decomposition- Throughout the heating process, the iron compound decomposes into iron oxide. The timeline and temperature of calcination determine the final particle size and color of the pigment.


• Grinding and cooling- The resulting pigment is cooled down and then ground to attain the desired particle texture and size.


• Natural methodology: Extraction from iron ore: Apart from the synthetic methodologies, iron oxide pigments can also be manufactured naturally from iron-rich ores like hematite (Fe2O3) and magnetite (Fe3O4). The strides in the natural production methodology include-


• Mining: Iron ores as mentioned above are extracted from the earth.


• Grinding and Crushing: The mined ore is squashed and ground into a fine powder.


• Separation: The iron oxide is parted from impurities through floatation or magnetic separation.


• Drying and Processing: The separated iron oxide is further processed to eliminate moisture and any remaining impurities. It is then dehumidified and compressed to the appropriate particle dimensions.

Applications of Iron Oxide Pigments

Iron oxide pigments are used in a plethora of industries due to their appealing color, resistance to fading and stability. Some of the prominent applications include:

• Coatings and paints- These pigments offer UV resistant and robust colors in architectural and industrial paints.


• Construction materials- These pigments are casted with concrete, bricks, tiles, and roofing materials to yield long lasting color.


• Plastics- They are utilized in plastic manufacturing for coloration without affecting the plastic’s inner architecture and integrity.


• Cosmetics- In the beauty industry, iron oxide pigments are used for safe and natural colorants in products like eyeshadow and foundation.