What type of pigment is zinc dust classified as in paint?

Zinc dust is classified as a sacrificial pigment in paint due to its unique properties that contribute to corrosion resistance. When added to coatings, it serves as a protective barrier by reacting with environmental elements, thus preventing rust on metal surfaces. This term "sacrificial" indicates that the zinc will corrode first before the underlying metal, effectively prolonging the life of the substrate.

In various applications, such as protective coatings for steel structures, the presence of zinc dust can significantly enhance durability and longevity by providing cathodic protection. This cathodic action means that if the paint layer is compromised, the zinc will corrode instead of the metal it protects.

The other types of pigments mentioned, such as base pigments, color pigments, and blocking pigments, serve different functions in paint formulations. Base pigments provide color and opacity without serving a protective role, color pigments primarily focus on imparting specific hues, and blocking pigments are used to hinder the passage of light or radiation (common in applications like sunscreen or protective coatings). None of these offer the same protective, galvanic role that zinc dust does.