The complete picture of what happens when aluminum is in contact with concrete involves differentiating between surface attack and attack involving structural damage to aluminum. When aluminum is in contact with fresh concrete, a surface reaction occurs between the aluminum and the alkaline constituents of the concrete resulting in a slight superficial attack on the metal. This attack occurs over the first four or five days and then subsides. In this four to five day period, aluminum will be etched to a depth of one-half to 1 mil. The attack, however, does not affect structural integrity. It does, though, affect appearance. A clear methacrylate coating properly applied will protect the aluminum and need not be removed.
The addition of chlorides can aggravate galvanic corrosion of aluminum in concrete. Galvanic corrosion can be prevented if aluminum is not allowed to contact other metals such as steel reinforcing rods. Coating the aluminum with an asphalt or bituminous paint is also another possible prevention method.