Iron oxide pigments are widely used in coatings, paints and inks because they are non-toxic, non-bleeding, low cost, and can form a variety of different tones. Coatings are composed of film-forming substances, pigments, fillers, solvents and additives. It has developed from oil-based coatings to synthetic resin coatings. All kinds of coatings are inseparable from the application of pigments. In particular, iron oxide pigments for paint and coatings have become indispensable pigments in the coating industry.
Iron oxide pigments used in paint and coatings include iron yellow, iron red, iron black, mica iron oxide, transparent iron yellow, transparent iron oxide red, translucent products, etc. Among them, red iron oxide is the most widely used.
>>> Why Iron Oxide Pigments Can Be Widely Used in Paint And Coatings
Iron oxide pigment has good heat resistance and stable chemical properties. Its performances of dilute acid resistance, alkali resistance, water and solvent resistance make it with good weather resistance.
Iron oxide pigments for paint and coatings have good weather resistance, high purity, good thermal stability, good compatibility with other components in the application system. It can absorb ultraviolet rays, prevent base material degradation. Meanwhile, it has a protective effect on the coating, and are low in cost. That’s why it is suitable for paints and coatings. Because of its strong hiding power, strong impermeability to ultraviolet rays and low water absorption, it can enhance the mechanical strength of the paint film, especially the excellent characteristics in terms of adhesion. Now iron oxide is widely used in various outdoor paints, traffic paints, metal antirust primers and top paintings.
>>> Requirements of the Iron Oxide Properties for Anti-rust paint
- The water-soluble salt of red iron oxide used in anti-rust paint should be low, which it is beneficial to improve the anti-rust performance. Especially when the chloride iron increases, the water will easily penetrate into the coating and accelerate the corrosion of the metal at the same time.
- 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, the coating made of iron red paint is prone to pulverization. Especially iron red with a smaller particle size is faster to pulverize. So in order to improve weather resistance, Iron red pigment with a larger particle size will be better. But it is easy to make the coating shiny decline.
>>> Requirements of the Iron Oxide Properties for Topcoating
Flocculation of one or more pigment components usually cause the color change of topcoating. In addition, poor wettability of pigments and too many wetting agents are often the causes of flocculation. Pigments are prone to flocculation after roasting. Therefore, in order to make the color of topcoating uniform, using synthetic red iron oxide produced by wet process will be better. The surface of the coating made of needle-like crystals of iron red is prone to mercerization. View the stripes produced when painting from various angles. The color intensity is different, which is related to the different refractive index of the crystal.
>>> Different Types of Iron Oxide Pigments for Paint And Coatings
- Compared with natural red iron oxide, synthetic iron red has larger density, small particle size, high purity, good hiding power, high oil absorption, and strong coloring power. In some coating formulations, both types are used, such as alkyd primers used for primers on ferrous metal surfaces.
- The heat resistance of iron yellow is slightly worse. During the heat treatment, it will gradually lose the crystal water and transform to the red phase. So it can’t be used in coatings with higher drying temperatures. Synthetic yellow iron has high tinting power and brighter shade. It can produce yellow iron oxide of various hues as needed. It also has the function of shielding ultraviolet light radiation. In addition, it can extend the application life of the coating. The application area and quantity of iron yellow in the paint are small. It is often used in the combination with other pigments. In the coloring of latex paint, a small amount of iron yellow colorant can be added to make it beige.
- Iron brown and iron black often contain dopants such as carbon and manganese oxide. The synthetic product is a blend of iron black, iron red and iron yellow, with high tinting power and hiding power.
- Iron oxide brown can absorb almost all the ultraviolet spectrum, so the camouflage paint made of iron brown has the same infrared reflection as trees, grass, sand, etc., making it impossible to detect the camouflage by infrared photography in the air. Iron oxide black can be used for preparation primers, used for the primer of metal objects in vehicles and transportation equipment, and is easier to grind than carbon black.