ABSTRACT
Protective pigments come in three major types: sacrificial, inhibitive, and barrier. Zinc-rich paints, or zinc-rich primers, (ZRPs) have been used to protect steel construction for many decades, and zinc dust is now the most widely used protective pigment in paint. There are two classes of ZRPs, which differ depending on the binder used: organic and inorganic. This chapter discusses some phosphate pigments including the zinc phosphates and one type of nonzinc phosphate, aluminum triphosphates. Another phosphate pigment that has been studied is lauryl ammonium phosphate. Ferrite pigments appear to protect steel both by creating an alkaline environment at the coating– metal interface and, with certain binders, by forming metal soaps. Other types of inhibitive pigments discussed in the chapter include calcium-exchanged silica, barium metaborate, molybdates, and silicates. Commonly used barrier pigments are: (1) Mineral-based materials, such as mica, micaceous iron oxide (MIO), and glass flakes; and (2) Metallic flakes of aluminum, zinc, stainless steel, nickel, and cupronickel.
