Some of theses, notably and , have better corrosion-resistance properties than others. More generally, 1xxx, 3xxx, 5xxx and 6xxx series alloys offer good corrosion resistance. Anodizing is a kind of surface oxidation that can produce some very attractive finishes. Leave some aluminum exposed and you risk corrosion getting a toehold. Ideally, keep the aluminum dry.
Many boaters also use a sacrificial anode made of zinc. This corrodes faster than the aluminum, in effect, sacrificing itself. Sacrificial anodes do need replacing periodically, but then so will most coatings. In the movie Tony Stark says he moved on from the original iron suit to one made of a gold-titanium alloy.
They suggest a better option would be Nitinol, an alloy of nickel and titanium. You can request Nitinol for your next fabrication project if you want, but it may work out to be a little expensive. Maybe he should find a plating service that can help him protect his metal components.
Rust vs Corrosion Most metals want to corrode back to some form of ore. Aluminum corrosion can occur gradually over weeks, months, or even years. With enough time, aluminum products can develop large holes due to corrosion. Kloeckner Metals is a full-line aluminum supplier and service center. Download our aluminum spec sheet and check what Kloeckner Metals routinely stocks. Aluminum Spec Sheet. Generally speaking, aluminum and its alloys have excellent resistance to corrosion.
Aluminum in its natural state, commercially pure or 1xxx aluminum, has the best corrosion-resistance, but that quality is compromised as alloys, particularly copper and iron but also magnesium or zinc, are added. The alloying elements used to achieve desirable properties of most commercial aluminum alloy groups are listed below.
These elements, added in small percentages, are added to give the metal desired properties of strength, ductility, weldability, machinability, corrosion resistance, and others. Paradoxically, aluminum oxidation is a central part of its corrosion resistance.
Aluminum has a very high affinity to oxygen. When a new aluminum surface is exposed in the presence of air or any other oxidizing agent, it quickly develops a thin, hard film of aluminum oxide or hydrated oxide in non-stagnant water. This aluminum oxidation is precisely what makes aluminum so corrosion-resistant. This film is relatively inert chemically. The corrosion resistance of aluminum relies on the inactivity of this surface film of aluminum or hydrated oxide. This surface film is generally stable in a pH range of about 4.
The film can stay stable in other cases depending on the environment, for example, nitric acid at pH 0, glacial acetic acid at pH3, or ammonium hydroxide at pH The oxide film can be dissolved in most strong acids and bases, in which case the corrosion of the aluminum will be rapid.
As with all common architectural and structural, aluminum will corrode under certain conditions. This is more likely to occur when the wrong alloy is chosen for projects or applications. To get good results with aluminum, it is essential to know the following:. The other co-authors of the May 12 Science article are Peter J. Eng, Mathew Newville, Steven R. Sutton and Mark L. Waychunas of the Lawrence Berkeley National Laboratory. All Rights Reserved. Stanford, CA Terms of Use Copyright Complaints.
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