Qxidizers and Halogens 17-8

Oxidizing agents react with carbon to form carbon dioxide and/or carbon monoxide. The new compound, that is formed, will destroy carbon/graphite mechanical seal faces. Here is a list of some of the common oxidizers:

• Aqua Regia (a combination of nitric and hydrochloric acid) used for dissolving metals.
• Oleum, used in the manufacture of detergents and explosives.
• Perchloric acid, used in the manufacture of medicine, explosives, and esters .
• Sulfur trioxide, used to manufacture sulphuric acid.
• Nitric acid, used in fertilizer, dyeing, explosives, drugs, etching and medicine.
• Hot sulphuric acid, the most widely used industrial chemical.
• Chloric acid, ignites organic material on contact.
• Chlorous acid, over 200 degrees Fahrenheit (100 C).
• Ferric chloride, used in sewage treatment photography, medicine and feed additives.
• Hydrofluoric acid, used for etching, cleaning castings and fermentation.
• Sodium hypochlorite, used in bleaching paper pulp, textiles, and tanning textiles.
• Methyl Ethyl Ketone (MEK) a common solvent.
• Perchloric Acid - 2N

Additionally, look for any chemical whose name contains the word:

• Peroxide
• Chlorate
• Perchlorate
• Nitrate
• Permanganate

The Halogens are another group of chemicals that will attack carbon:

• Chlorine
• Fluorine
• Bromine
• Astintine
• Iodine

The degree of attack will be affected by the oxidizer's chemical concentration and temperature. If you are handling any of these chemicals it would pay to test an unfilled carbon for compatibility prior to installing a mechanical seal.

In addition to the above chemicals, experience teaches us that all grades of carbon should be avoided in the following applications:

• If there is a possibility of color contamination of the product. Some paper and paint applications have this problem.
• If you're sealing hot oil and have to meet fugitive emission standards.
• Some de-ionized water applications can attack carbon

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