Fouling of heat exchanger tubes is usually defined as deposition of non-scale-forming materials such as:

1. silt or iron suspended in makeup wat
2. naturally occurring organics in makeup water
3. particulate matter scrubbed from the atmosphere
4. deposition of chemical additives due to poor control
5. organic contamination from process leaks
6. migrating corrosion products

The following is a brief description of some frequently encountered foulants in industrial cooling water systems.