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Corrosive

Definition

A corrosive material is a highly reactive substance that causes obvious damage to living tissue. Corrosives act either directly, by chemically destroying the part (oxidation), or indirectly by causing inflammation. Acids and bases are common corrosive materials. Corrosives such as these are also sometimes referred to as caustics. Typical examples of acidic corrosives are hydrochloric (muriatic) acid and sulfuric acid. Typical examples of basic corrosives are sodium hydroxide and lye. The OSHA definition of corrosive in 29 CFR 1910.1200 App A is: "Corrosive: A chemical that causes visible destruction of, or irreversible alterations in, living tissue by chemical action at the site of contact. For example, a chemical is considered to be corrosive if, when tested on the intact skin of albino rabbits by the method described by the U.S. Department of Transportation in appendix A to 49 CFR part 173, it destroys or changes irreversibly the structure of the tissue at the site of contact following an exposure period of four hours. This term shall not refer to action on inanimate [non-living] surfaces." Rust and electrochemical oxidation are forms of corrosion that occur on metals, but a) these occur on a much slower time scale and b) these are not a health effect and, therefore, are not usually noted on an MSDS except perhaps in storage recommendations. The U.S. Department of Transportation includes metal in their definitions.

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Additional Info

Corrosive materials pose serious immediate risk to skin, tissues, eyes and other parts of the body. Any body part coming in contact with a corrosive material must be flushed with water IMMEDIATELY and then medical attention or opinion should be sought.

Almost every medical resource, consensus standard, and MSDS says that the water flushing should last 15 minutes, however there is some question whether such long flushing periods may offer significant benefit in all cases, particularly when it could unnecessarily delay the course of emergency treatment.

For example, with a particularly dangerous chemicals such as concentrated hydrofluoric acid, rinsing more than 5 minutes would undoubtedly be less effective than administering treatment with calcium gluconate gel. Likewise, if a chemical accident involves traumatic injuries, a shorter rinse period may be necessary in order to stem bleeding etc.

The Canadian Centre for Occupational Health & Safety has noted that some references have indicated: The flushing or rinsing time can be modified if the identity and properties of the chemical are known. For example: a minimum 5-minute flushing time is recommended for mildly irritating chemicals, at least 20 minutes for moderate-to-severe irritants, 20 minutes for non-penetrating corrosives, and at least 60 minutes for penetrating corrosives. Non-penetrating corrosives are chemicals which react with human tissue to form a protective layer which limits the extent of damage. Most acids are non-penetrating corrosives. Penetrating corrosives, such as most alkalis, hydrofluoric acid and phenol, enter the skin or eyes deeply. Penetrating corrosives require longer water flushing (a minimum of 60 minutes) than non-penetrating corrosives (a minimum of 20 minutes). Note that while the CCOHS advice is a sensible risk-based approach, we would not recommend that anyone delay treatment of an hydrofluoric acid exposure for 60 minutes! As should be readily apparent by now, the flushing period that gives the best clinical outcome for the victim is going to depend on the nature of the chemical, its concentration, the availability of medical treatment, the available water temperature, the condition of the victim and many other factors. The bottom line is that "15 minutes" is a rule of thumb (or best guess), not an ironclad rule. The actual time necessary in a given situation may be shorter or longer.

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Corrosives that are inhaled or ingested (eaten) must be dealt with by medical professionals. DO NOT induce vomiting for ingestion of a corrosive material as additional damage to the esophagus, throat and mouth will occur upon regurgitation. Consult the MSDS, an emergency room and/or your poison control center for first aid procedures in the event of ingestion.

MSDS Relevance

As required by Paragraph e of the OSHA Hazard Communication standard, workplaces using any hazardous chemical must have a written plan that includes labeling, information, MSDS's, and training in the hazards associated with those chemicals. In addition, a number of additional OSHA standards for eye protection etc. also apply to the use of corrosive chemicals. See our PPE entry for more information.

Note: Although this is not explained on most MSDS's, corrosives can also etch or pit metals such as stainless steel. This can occur without visible surface damage, but stress cracks invisible to the naked eye can form. These microscopic cracks can severely weaken or degrade the material, leading to unexpected failure (or explosions in the case of pressure vessels).

Further Reading

Safety With Corrosive Chemicals (PDF file) at the Department of Labour, New Zealand List of corrosive chemicals courtesy of Columbia University. U.S. Department of Transportation's (DOT) Pipeline and Hazardous Materials Safety Administration's HazMat Safety Community. Dozens of electrochemistry and corrosion links at steelynx.net. How Do I Work Safely with Corrosive Liquids and Solids? at the CCOHS. See also: acid, base, eye wash, pH, PPE, vesicant. Additional definitions from Google and OneLook.

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Disclaimer: The information contained herein is believed to be true and accurate, however ILPI makes no guarantees concerning the veracity of any statement. Use of any information on this page is at the reader's own risk. ILPI strongly encourages the reader to consult the appropriate local, state and federal agencies concerning the matters discussed herein.