Corrosiveness
Common corrosives are either strong acids or strong bases, or concentrated solutions of certain weak acids and weak bases.
Their action on living tissue is based on acid-base catalysis of ester and amide hydrolysis. Both corrosive acids and corrosive bases are able to destroy skin by catalyzing the hydrolysis of fats, which are chemically esters. Proteins are chemically amides, which can also be hydrolyzed by acid-base catalysis. Strong acids and bases denature proteins and also dehydrate them easily. Dehydration removes water from the tissue and can be significantly exothermic. Some corrosives, for example, concentrated sulfuric acid causes secondary thermal burns in tissue in addition to chemical burns due to the heat generated by a dehydration reaction with carbohydrates. Strong oxidizing agents, such as concentrated hydrogen peroxide, can also be corrosive to tissues and other materials, even when the pH is close to neutral. Nitric acid is an example of a strong acid that is also a strong oxidizer, making it significantly more corrosive than one would expect from the pKa alone.
There are also more specific corrosives. Hydrofluoric acid, for example, is initially painless in lower concentrations and is technically a weak acid, but it produces fluoride ions (the actual corrosive species) after the acid is painlessly absorbed. Although zinc chloride solutions are acidic by the Brønsted definition, the zinc cation also specifically attacks hydroxyl groups as a Lewis acid. This explains the ability of zinc chloride solutions to react with cellulose and corrode through paper and silk.
Corrosives may be of any state of matter: liquids, solids, gases, mists or vapors.
Corrosive substances are most hazardous towards eyesight: a drop of a corrosive substance readily causes blindness within 2–10 seconds through opacification or destruction of the cornea.
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