Iron oxide pigments are widely used in coatings, paints, and inks due to their non-toxic, non bleeding, low cost, and ability to form various shades. Coatings are composed of film-forming substances, pigments, fillers, solvents, and additives. It has developed from oil-based coatings to synthetic resin coatings, and various coatings cannot do without the application of pigments, especially iron oxide pigments, which have become an indispensable pigment variety in the coating industry.

Iron oxide pigments used in coatings include iron yellow, iron red, iron brown, iron black, mica iron oxide, transparent iron yellow, transparent iron red, and translucent products, of which iron red is the most important one in large quantities and wide range.
Iron red has excellent heat resistance, does not change color at 500 ℃, and does not change its chemical structure at 1200 ℃, making it extremely stable. It can absorb the ultraviolet spectrum in sunlight, so it has a protective effect on the coating. It is resistant to dilute acids, alkalis, water, and solvents, making it have good weather resistance.

The Granularity of iron oxide red is 0.2 μ M, the specific surface area and oil absorption are also large. When the Granularity increases, the color moves from red phase purple, and the specific surface area and oil absorption become smaller. Iron red is widely used in anti rust coatings with physical anti rust function. Moisture in the atmosphere cannot penetrate into the metal layer, and can increase the density and mechanical strength of the coating.
The iron red water soluble salt used in anti rust paint should be low, which is beneficial for improving anti rust performance, especially when chloride ions increase, water is easy to penetrate into the coating, and at the same time, it also accelerates metal corrosion.

Metal is very sensitive to acid, so when the PH value of resin, pigment or solvent in the paint is below 7, it is easier to promote metal corrosion. After long-term exposure to the sun, the coating of iron red paint is prone to powdering, especially the iron red with smaller Granularity is powdering faster, so iron red with larger Granularity should be selected to improve weather resistance, but it is also easy to reduce the gloss of the coating.

The change in color of the topcoat is usually caused by flocculation of one or more of the pigment components. Poor wettability of the pigment and too many wetting agents are often the reasons for flocculation. After calcination, the pigment has a significant tendency to flocculation. Therefore, in order to ensure uniform and consistent color of the topcoat, it is advisable to choose wet synthesis of iron red. The coating surface made of needle shaped crystalline iron red is prone to mercerization, and the stripes generated during painting are observed from various angles, with different color intensities, and are related to the different refractive indices of the crystals.

Compared with natural products, synthetic iron oxide red has higher density, smaller Granularity, higher purity, better hiding power, higher oil absorption and stronger coloring power. In some paint formulations, natural iron oxide red is shared with synthetic products, such as iron oxide red alkyd primer used for priming Ferrous surfaces such as vehicles, machines and instruments.