Letter 25060

Rusting Aluminum  

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I need a link or web address that I can down load printed matter explaining that aluminum does not rust.

I am having a problem with a stupid contractor that thinks my aluminum curtain wall with a clear anodized finish is rusting when in fact it is metal shavings from welding and grinding operations rusting on the aluminum and staining it.

I have searched several sites and have not found exact wording that "aluminum does not rust".

Thanks,

Dick Bateman
comercial glass & glazing - Tallahassee, Florida, USA

The term "rust" has several meanings. The most common refers to iron oxide and is a reddish-brown colored corrosion. Aluminum can not form iron oxide since it contains only trace amounts of iron if any at all, so it will never corrode a "rust" color. Somewhere along the line the term rust also started meaning corrosion in general, and of course aluminum can corrode but it is generally whitish in appearance and looks nothing like iron oxide. So you could always give them the definition of rust as iron oxide and give them your alloys content thus proving iron is not present so therefore can't rust brownish color.

As for websites, Mr Mooney in letter 13762 on this website has the wording "aluminum doesn't rust". I also did a google.com search and came up with several results, choose which you like the best.

Good luck,

Jason Aube
- Flint, MI, USA

Aluminum oxidizes forming a natural barrier to resist corrosive effects. Anodized aluminum, is an aluminum that has an extra thick layer, of this oxidized material, created through an electrical process. IF aluminum came into direct contact with mercury, this oxidized layer on the surface of the aluminum is destroyed. The effects of moisture in the air would then, rust the aluminum to pieces. Theoretically, if a sufficient amount of mercury paste were applied to an aircraft body made of aluminum, it would not be air worthy of flight, in a very short period of time. The structure of the aircraft would disintegrate. So yes aluminum will violently rust, but only through direct contact with its chemical enemy, mercury.

Michael scott ford
- West Frankfort,IL,Franklin

As Jason Aube implies, there is a semantics issue here. There is no question that aluminum reacts with air and oxidizes, as do all metals with the exception of gold, platinum, and a few other precious metals.

But many authoritative sources define rust as the familiar red-brown oxides of iron, and aluminum cannot corrode with those red-brown reaction products because they are the products of oxidation of iron and aluminum has no or negligable iron in it.

To Mr. Bateman's original situation: he is right that weld spatter or iron shavings account for the rust color; it's not the aluminum.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Aluminum is a very unstable material and to add to the H20 article on mercury paste my air conditioner outside unit had to be replaced because the ALU could would fall apart with a light touch.

Nothing last forever.

Except Gold ????

John Chandler
- Fort Lauderdale, Florida

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