Definition - What does Precipitation mean?

Precipitation is the process of removal of solid or liquid particles from a fluid. In metals, this is the separation of a new phase from a solid or liquid solution, usually with changing conditions of temperature, pressure or both.

Precipitation reactions can be used for making pigments, removing salts from water in water treatment, and in classical qualitative inorganic analysis. It is also useful to isolate the products of a reaction during workup. It is used to purify materials from contaminates and reduce corrosion.

Corrosionpedia explains Precipitation

Precipitation is the creation of a solid in a solution or inside another solid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid solution, the solid formed is called the precipitate. The chemical that causes the solid to form is called the precipitant. Without sufficient force of gravity (settling) to bring the solid particles together, the precipitate remains in suspension.

Precipitation may occur when an antisolvent (a solvent in which the product is insoluble) is added, drastically reducing the solubility of the desired product. Precipitation may occur if the concentration of a compound exceeds its solubility (such as when mixing solvents or changing their temperature). Thereafter, the precipitate may easily be separated by filtration, decanting, or centrifugation.

In metallurgy, precipitation from a solid solution is also a useful way to strengthen alloys; this process is known as solid solution strengthening. Precipitation is also useful in purifying products or removing contaminations. Contaminants' precipitation in heat exchangers or boilers causes scale formation which leads to corrosion.

In solids, precipitation occurs if the concentration of one solid is above the solubility limit in the host solid, due to processes such as rapid quenching or ion implantation, and the temperature is high enough that diffusion can lead to segregation into precipitates. Precipitation in solids is routinely used to synthesize nanoclusters. An important stage of the precipitation process is the onset of nucleation.

Precipitation can cause atmospheric corrosion and hardening of metal alloys.

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