Pigment materials usually possess special properties that make them ideal for coloring materials, and they provide permanence and stability of materials.
Pigments are finely ground colorants which are insoluble. A pigment changes the color of reflected or transmitted light through wavelength-selective absorption. Pigments can be natural or synthetic products. They are used in paints and coatings as coloring agents as well as corrosion protection and water barriers.
While pigments and dyes are both colorants, a pigment is not the same as a dye. Pigment is insoluble in its vehicle, whereas a dye is either itself a liquid or is soluble in its vehicle. There are some instances that a soluble dye with a metallic salt can be used to produce a pigment. This type of pigment is known as a lake pigment.
A pigment must possess high tinting strength properties and be stable in solid form at ambient temperatures. Pigment selection for a particular application depends on its cost and requirements of the pigment’s physical properties and attributes.
The two terms rust stimulators and rust inhibitors are derived from pigments and corrosion. Rust stimulators are particular pigments that result in active corrosion. Pigments which show the least corrosive action are called rust inhibitors. Pigments that lie between these two groups are known as inert.
Metal pigments are very important in industrial coatings. They are used for protecting metallic surfaces from corrosion. For emulsion paints or varnishes, the color is the most important selection criterion. For metal pigment coatings, corrosion protection is the most important factor for selecting them to use in industry.