Definition - What does Vapor mean?

A vapor is a substance in the gas phase at a temperature lower than its critical point. It is the gaseous product of evaporation. Vapor can be deposited on material surfaces in coatings or paints. It can also be used in vapor plating. Vapor of some chemicals and some strong acids causes corrosion of materials. The vapors of volatile acids and bases commonly cause corrosion of plumbing fixtures.

Vapor is responsible for the familiar processes of cloud formation and condensation. It is commonly employed to carry out the physical processes of distillation and headspace extraction from a liquid sample prior to gas chromatography.

Corrosionpedia explains Vapor

Vapor is a gas phase at a temperature where the same substance can also exist in the liquid or solid state, below the critical temperature of the substance. For example, water has a critical temperature of 705°F (374°C), which is the highest temperature at which liquid water can exist. If the vapor is in contact with a liquid or solid phase, the two phases are in a state of equilibrium. The constituent molecules of a vapor possess vibrational, rotational and translational motion. These motions are considered in the kinetic theory of gases.

Vapor-form corrosion inhibitors have significant uses in the fuel industry to protect against rust and corrosion. They provide exceptional product protection without the labor-intensive clean-up required with conventional oil coatings or other inhibiting products — even for previously corroded, painted or coated surfaces.

Retarder in vapor form is also used to protect foil from corrosion. For example, water and/or condensed moisture on the surface of the foil are the single largest cause of corrosion. When water remains in contact with aluminum foil, the metal begins to corrode and stains appear on the surface. It can be prevented by using vapor retarders.

High temperature and moisture vapor can cause rapid corrosion. Corrosive gases and vapors are hazardous to all parts of the body; certain organs, such as the eyes and the respiratory tract, are particularly sensitive. Acid vapors eventually lead to the corrosion of metal fixtures, storage cabinets and shelves. Therefore, proper precautions are required when dealing with corrosive vapors in laboratories as well as industries.

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