*11.5.4.7 Precipitation inhibitors*

These are compounds that forms precipitates on the metal surface, thereby providing a protective film. The most common inhibitors of this category are the silicates and the phosphates. For example, Sodium silicate, is used in many domestic water softeners to prevent the occurrence of rust [57, 58].

**Figure 14.** *Schematic representation of vapor phase inhibitors.*

**Figure 15.** *Schematic representation of volatile inhibitors.*
