Chemical Properties of Aluminum Foil


Aluminum foil is a solid sheet of aluminum, or of an appropriate aluminum alloy, rolled very thin, varying from a minimum thickness of about 0.00017 in. to a maximum of about 0.0059 in.. From the standpoint of packaging and other principal applications, one of the most important characteristics of aluminum foil is its impermeability to water vapor and gases. Bare foil one mil and thicker is completely impermeabl, much thinner gauges laminated to an appropriate film form impervious composite materials, making them ideal for packaging and general insulation/barrier applications which, with solid foil semi-rigid containers, account for most foil consumption.

While most aluminum foil is employed in packaging, its many unique properties also account for its use in literally hundreds of other applications.

Resistance of aluminum foil to chemical attacks depends upon the specific compound or agent, but it has excellent and good compatibility with most products. Even some of the compounds classified as only fair in this respect are frequently packaged in coated or film-laminated foils.

Aluminum has high resistance to most fats, petroleum greases, and organic solvents. Intermittent contact with water generally has no visible effect on aluminum, otherwise, exposed to clean air. However, standing water in the presence of certain salts and caustics can be corrosive. For example, some hygroscopic products packaged in aluminum foil may cause some reaction, particularly if the product contains salt or some mild organic acid. In these or any other applications which may subject the aluminum to mild attack, coating or lamination protection is employed on the foil surface next to the product.

In general, such food products as candies, milk, unsalted meats, butter and margarine are compatible with bare aluminum. They also greatly benefit from its opacity, which retards deterioration from exposure to light. Similarly, many drug and cosmetic products are compatible with aluminum foil and also must be protected from light.

Aluminum resists mildly acidic products better than it does mild alkaline compounds, such as soaps and detergents. While use with the stronger concentrations of mineral acids is not recommended without proper protection because of possible severe corrosion, weak organic acids, such as those found in foods generally, have little or no effect on aluminum. Reliable information and suitable tests are always recommended.