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Last updated: May 15, 2018

What Does Desiccant Mean?

A desiccant is a substance or chemical that absorbs or attracts moisture from the air, causing a state of dryness (desiccation) in its vicinity. This chemical used to attract and remove moisture from air or gas and keep the products dry which, in turn, inhibits the corrosion process.

These chemicals are used in product containers during shipping to protect against moisture damage. Descants also prevent condensation of moisture between window panes. Desiccants are available in various forms and are widely used in many industries, such as:

  • Packing
  • Electronics
  • Manufacturing

Corrosionpedia Explains Desiccant

Desiccants are chemical substances used as drying agents with a high attraction or affinity for water. They are usually chemically inert and do not react with water or the substances they protect. They use an adsorption mechanism to capture moisture and stow it away where it cannot interact with the product. Industrially, desiccants are widely used in gas streams to control water levels.

Silica is the most common desiccant. It is an inert, nontoxic, water-insoluble white solid. Other desiccants include:

  • Activated charcoal
  • Calcium sulfate
  • Calcium chloride
  • Molecular sieves (typically zeolites)

Desiccant bags like silica bags are used in package contents to protect against humidity during transport and storage. It also helps to prevent corrosion, mold growth and other harmful consequences of moisture through absorption of water vapor.

Desiccants are sold in desiccant units. A desiccant unit is the measure of the quantity of desiccant which, at equilibrium with air at 23 ± 35.5°F (2°C), adsorbs the following quantities of water vapor:

  • Min. 3.0 g at 20% relative humidity
  • Min. 6.0 g at 40% relative humidity

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