Aluminum seals are often seen as being more corrosion-resistant than steel. But aluminum is not impervious to corrosion even if the aluminum can form a protective coating on its own. You may need to provide your own protective coating to the aluminum seal depending on the conditions under which your product will be kept.
Aluminum becomes dull as a result of corrosion, which causes calcium, lime, tarnish, oil and hard water stains to accumulate on the aluminum. This residue can be washed off with aluminum pre-clean chemicals that can bring back the shine. However, be careful with the types of chemicals you use. High-pH cleaners, such as an oven cleaner, can actually dissolve and destroy aluminum.
Pitting can occur in aluminum seals and can cause them to fail if the aluminum is continuously exposed to water. Pitting occurs when the aluminum is exposed to electrolytes that have chloride anions. The pitting usually occurs on grain boundaries. The seal should be removed and thoroughly dried. Then, the seal could be sanded down to eliminate pits. Afterward, the aluminum should be buffed.
Preventing a Uniform Attack
A uniform attack is another way in which aluminum seals are destroyed. In this case, the corroding substance attacks all of the aluminum seal at once, thinning it and making the seal less likely to resist pressure. Inhibitors can protect aluminum from corrosion, such as chromic acid. Also, some sealers might use sacrificial zinc coatings to prolong the life of the aluminum seal.
Some metals react poorly to others and will corrode. Aluminum is vulnerable to copper and brass. Therefore, if your product contains either of these metals, they must be kept separate from the aluminum.
Some aluminum alloys are vulnerable to very acidic substances. All aluminum alloys are vulnerable to high pH substances. Therefore, water that contains a lot of copper or carbonates can corrode aluminum seals. Adding ethylene glycol or the less toxic propylene glycol to water can help prevent corrosion. These liquids come with corrosion inhibitors that will protect the aluminum seals.
Protecting Aluminum from Specific Corrosive Substances
Some substances can interfere with aluminum's protective coating, such as mercury. When it doesn't have a protective coating, aluminum rusts much more quickly than iron. Therefore, when selecting an aluminum seal, do not fully relax. While there are less headaches than other options, you will still need to protect your aluminum.