I'm leaning toward peeling since the affected area is shinier than normal finish. Crappy picture..

[hatehereyes]

From that picture it looks like it's peeling...

Maybe from your palm/thumb when pressing the space bar.

[ghporter]

Not "peeling." Wear of the finish is what I'd call it.

[hatehereyes]

Originally Posted by ghporter 

Not "peeling." Wear of the finish is what I'd call it.

Yeah, either way it's not dirt.

It's getting worn down.

[Cold Warrior]

Mine is doing the same thing, just in a couple different small areas. I've had it since October 2006 and I'm not surprised given how much I use it.

[Zeeb]

That's odd, what is peeling off exactly? I thought the aluminum was bare and not coated with anything that could peel--that often comes up when people discuss dark scratches on their aluminum MBP. Is it a dirt film which is coming off?

[Atheist]

^ I was wondering the same thing. How does aluminum peel?

[Cold Warrior]

The peeling is in a very specific area -- the long strip of material between keys and main body. Perhaps that strip is not aluminum?

[amazing]

My old 12" looks just like that--I concluded (like Cold Warrior) that the strip wasn't aluminum.

[Jasoco]

It's wearing down all right. Same thing has happened to my mouse. The indentation where my thumb rests on my MX1000 has both a super smooth area and an area that looks ribbed, as if my thumb nail dug into it repeatedly over the last 4 years.

[Eriamjh]

My 2006 MBP has wear below the left command key. Oh, well!

[macforray]

What we "see" as bare aluminum on finished products is almost always coated with something. The most common is an anodize coating. It can be clear or colored (as in those nicely colored aluminum iPods). The good thing about anodize is that it does penetrate the aluminum slightly, so minor wear areas should be okay.

Bare aluminum left to the everyday elements will oxidize, which is a white powdery substance on the surface of the aluminum. You can just imagine what this stuff would do to the electronics inside.

Painted aluminum products are coated with a conversion coating ("Chem Film") prior to painting to both prevent oxidation and improve paint adhesion.

[ghporter]

Originally Posted by macforray 

Bare aluminum left to the everyday elements will oxidize, which is a white powdery substance on the surface of the aluminum. You can just imagine what this stuff would do to the electronics inside.

Bare aluminum left to the everyday elements will oxidize, which is a white powdery substance on the surface of the aluminum. You can just imagine what this stuff would do to the electronics inside.[/QUOTE]Bare, uncoated aluminum will react very quickly with atmospheric oxygen to form a layer of aluminum oxide that "passivates" the surface, effectively sealing it against further corrosion. Just plain aluminum, without any surface treatment, will look slightly dull due to this thin, but effective layer.

The only time you will see a "powdery, white" corrosion in aluminum is when some agent other than just air contact causes the corrosion. Leaking alkaline batteries, spills of soft drinks (phosphoric acid gives colas their "bite" but it also can enhance corrosion), or other active chemicals will do this. Interestingly, human perspiration can be extremely corrosive to certain materials, including aluminum, due to its high water and salt content, along with other chemistry which is typically unique to the individual.

So your MBP or MacBook isn't going to dissolve into a powdery mass, but if you have already noticed that YOUR sweat impacts materials such as paint (especially on plastics) or other metals, you should expect some extra wear on your aluminum hardware.