Zone of Aeration

Definition - What does Zone of Aeration mean?

The zone of aeration is the region between the earth's surface and the water table. The main components of this region are the soil and rocks. Their pores are at times partly filled with water and air, and aeration occurs when the air and water mix or come into close contact.

The presence of water and oxygen gives rise to the formation of soil moisture, which influences the rate of corrosion when it comes into contact with metallic objects buried in the ground.

The zone of aeration is also known as the unsaturated area, vadose zone or zone of suspended water.

Corrosionpedia explains Zone of Aeration

The depth and composition of the zone of aeration differ from one area to another and the percentages of the different components are affected by factors such as:

  • Altitude
  • Climate
  • Type of soil and its structure
  • Human activity
  • Type of rock
  • Vegetation
  • Landscape

The ground water in the aeration zone may come from several sources and the main ones are through:

  • Infiltration of the surface water from rain, rivers and waste water
  • Capillary effect of the water from the saturation zone below the water table

These variations in the amount of water and air in the zone affect the oxygen and hence the moisture content in the aeration zone. The rate of corrosion increases as the oxygen amount in the water increases.

The same metallic object may corrode differently when buried at different locations. It is also possible to have an object with more corroded sections than others, despite the fact that it is made of the same material and buried at the same place.

Other factors that affect the rate of corrosion on a metallic object buried in the zone are:

  • Presence of other metals
  • Other materials in the soil
  • Impurities in the water
  • Type of metal
  • Protective coating

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