Corrosive Definition in Chemistry

Corrosive refers to a substance that has the power to cause irreversible damage or destroy another substance by contact. A corrosive substance may attack a wide variety of materials, but the term is usually applied to chemicals that can cause chemical burns upon contact with living tissue. A corrosive substance may be a solid, liquid, or gas.

The term "corrosive" comes from the Latin verb corrodes, which means "to gnaw". At low concentrations, corrosive chemicals are typically irritants.

The hazard symbol used to identify either a chemical capable of metal corrosion or skin corrosion shows a chemical poured onto a material and a hand, eating into the surface.

Also Known As: Corrosive chemicals may also be referred to as "caustic", although the term caustic usually applies to strong bases and not acids or oxidizers.

Examples of Corrosive Substances

Strong acids and bases are commonly corrosive, although there are some acids (e.g., the carborane acids) that are very powerful, yet not corrosive. Weak acids and bases may be corrosive if they are concentrated. Classes of corrosive substances include:

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Definition of Corrosion

By Anne Marie Helmenstine, Ph.D.

• strong acids - Examples include nitric acid, sulfuric acid, and hydrochloric acid
• concentrated weak acids - Examples include concentrated acetic acid and formic acid.
• strong Lewis acids - These include boron trifluoride and aluminum chloride
• strong bases - These are also known as alkalis. Examples include potassium hydroxide, sodium hydroxide, and calcium hydroxide.
• alkali metals - These metals and the hydrides of the alkali and alkaline earth metals act as strong bases. Examples include sodium and potassium metal.
• dehydrating agents - Examples include calcium oxide and phosphorus pentoxide.
• strong oxidizers - A good example is hydrogen peroxide.
• halogens - Examples include elemental fluorine and chlorine. The halide ions are not corrosive, except for fluoride.
• acid anhydrides
• organic halides - An example is acetyl chloride.
• alkylating agents - An example is dimethyl sulfate.
• certain organics - An example is phenol or carbolic acid.

How Corrosion Works

Usually, a corrosive chemical that attacks human skin denatures proteins or performs amide hydrolysis or ester hydrolysis. Amide hydrolysis damages proteins, which contain amide bonds. Lipids contain ester bonds and are attacked by ester hydrolysis.

In addition, a corrosive agent may participate in chemical reactions that dehydrate skin and/or produce heat. For example, sulfuric acid dehydrates carbohydrates in skin and releases heat, sometimes sufficient to cause a thermal burn in addition to the chemical burn.

Corrosive substances that attack other materials, such as metals, may produce rapid oxidation of the surface (for example).

Safe Handling of Corrosive Materials

Protective gear is used for personal protection from corrosive materials. The equipment may include gloves, aprons, safety goggles, safety shoes, respirators, face shields, and acid suits. Vapors and corrosive chemicals with a high vapor pressure should be used within a ventilation hood.

It's important that protective gear be made using a material with high chemical resistance to the corrosive chemical of interest. There is no single protective material that protects against all corrosive substances. For example, rubber gloves may be fine for one chemical, yet be corroded by another. The same is true of nitrile, neoprene, and butyl rubber.

Uses of Corrosive Materials

Corrosive chemicals often make good cleaners. Because they tend to be highly reactive, corrosives may be used in catalytic reactions or as reactive intermediates in the chemical industry.

Corrosive Versus Caustic or Irritant

The term "caustic" is often considered synonymous with "corrosive." However, only strong bases should be referred to as caustic. Examples of caustic chemicals include sodium hydroxide and potassium hydroxide.

A dilute corrosive chemical acts as an irritant. However, at higher concentrations, corrosive chemicals produce a chemical burn.

While corrosive chemicals may be poisonous, the two characteristics are separate. A poison is a substance with a systemic toxic effect. Poisons may take some time to act. In contrast, a corrosive substance causes an immediate effect on tissue or a surface.