What Does Fouling Mean?
Fouling is the settlement, and sometimes the growth, of undesired materials on solid surfaces in a way that reduces the efficiency of the affected part.
Fouling may be caused by either the operating environment or by one of the equipment’s processes. It deteriorates protective coatings on the metals and reduces corrosion resistance as well as physical and mechanical properties of the material.
Fouling is a common phenomenon that occurs in a wide range of equipment and environments and can be caused by living organisms or by non-living deposits.
Corrosionpedia Explains Fouling
Fouling can be classified into two broad categories: microfouling and macrofouling. Macrofouling is caused by coarse matter of either inorganic or biological origin, such as animals and plants. An example is what occurs in heat transfer components in heat exchangers - the course matter may be contained in the polluted cooling waters or contaminated gases from the wind. This fouling can cause blockages or fretting damage.
Microfouling is caused by bacteria and unicellular algae (slime). Common types in this category are:
- Chemical reaction fouling
- Corrosion fouling
- Precipitation fouling
Composite fouling is caused by more than one fouling mechanism or foulant.
Marine fouling is a typical composite fouling and occurs due to seaweed, bacteria and other living organisms in the waters, which adhere to immersed surfaces such as ship hulls. The organisms settle on the surface and grow quickly, forming a layer that covers the surface, attracting and trapping more material.
The extent and severity of fouling is dependent on variables such as:
- Nutrient availability
- Water salinity
- Fouling materials
Surfaces affected include:
- Ship hulls and propellers
- Spark plug electrodes
- Electrical heating elements
- Solar panels
- Oil rigs
- Pipes used to carry water as a coolant for industrial power plants
Some effects of fouling are:
- Reduced efficiency
- Additional drag
- Deterioration of protective coating
- Decreased corrosion resistance
- Reduced lifespan of surfaces
- Decreased power output from solar panels
Fouling control and reduction are achieved by:
- Using antifouling paints
- Preventing fouling materials from entering systems
- Periodic cleaning to remove foulants
- Treatments to control water or air in the cooling towers