956Hydrotalcite Coatings

Although aluminum is often used without coatings, coatings are sometimes necessary for appearance or corrosion protection. Many coatings do not adhere well to aluminum, however, without a surface pretreatment. The most effective pre-treatment for many years has been a chromate coating, but the oxidizing solutions used to make chromate coatings and the coatings themselves contain hexavalent chromium (Cr6+), a carcinogen. Cyanide and other toxic substances are also commonly used in chromate coating operations. Anodizing is an alternate chromate coatings, but it is more expensive.

Environmental and worker safety issues have led to the search for alternate coating pretreatment methods. Recently, a hydrotalcite coating has been developed at the University of Virginia to take the place of chromate coatings. The hydrotalcite coating costs less than chromate, is nontoxic, and is effective with the low-copper (3xxx, 5xxx, and 6xxx series) alloys.

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