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**Mike Irwin** · February 5, 2002, 12:42 PM

What Labgrade is correctly saying is that aluminum exposed to air oxidizes VERY quickly to form a surface layer of Al2O3, Aluminum Oxide.

It has a hardness of 9 on the Mohs scale, diamond has a Mohs hardness of 10. Granted, the difference in absolute hardness between the two is about 300%, but it's still a good indication of how relatively soft aluminum oxidizes into a pretty abrasive chemical.

Pure aluminum has a Mohs hardness of 2.75, alloyed aluminum, of the kind that we normally see, is probably around 4 to 5.

Manufacturers who work with aluminum products know that there is going to be considerable wear attributed to aluminum oxide on the metal.

February 5, 2002, 12:42 PM	#12
Mike Irwin Staff Join Date: April 14, 2000 Location: Northern Virginia Posts: 41,642	What Labgrade is correctly saying is that aluminum exposed to air oxidizes VERY quickly to form a surface layer of Al2O3, Aluminum Oxide. It has a hardness of 9 on the Mohs scale, diamond has a Mohs hardness of 10. Granted, the difference in absolute hardness between the two is about 300%, but it's still a good indication of how relatively soft aluminum oxidizes into a pretty abrasive chemical. Pure aluminum has a Mohs hardness of 2.75, alloyed aluminum, of the kind that we normally see, is probably around 4 to 5. Manufacturers who work with aluminum products know that there is going to be considerable wear attributed to aluminum oxide on the metal. __________________ "The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza Baby Jesus cries when the fat redneck doesn't have military-grade firepower.