Heres the scoop fellow members, I have a 2005 S, the "chrome trim" above and below the side windows have these cloudy white water marks. I have priced out new ones (8 pieces over a $1,005.00) not going to happen here! So I tried wet sanding starting at 600 grit and worked my way up to 2000 grit, it worked but not well enough. Next step I tried "aircraft finish" remover nothing again. Next step was "paint remover" strike 3. I joined a "metal polishing" forum the guys there said the trim parts are anodized aluminum, not clear coated aluminum. They suggested oven cleaner with sodium hydroxide in it again same results nod-da. They even suggested a "drain cleaning gel" (for real) but yet again zip,zero nod-da results.
My question; What the heck is on this trim that will not allow one to polish it up or remove the coating to get to the bare aluminum?
Or if someone has had success in polishing the trim, PLEASE be kind and enlighten me.

Thank you

 

If it's a chrome shine you want, I'd suggest some of that chrome tape you can get at an auto parts store if the pieces aren't curved. Careful trimming with a razor blade and no one wil ever be able to tell the difference.

 

Not a metallurgist nor a chemist, but it is the 'sodium hydroxide' that will de-annodize the Aluminium, which is why they also suggested drain cleaner.

You do this at your own risk.

First off protective gloves etc required. And do not breath the vapour.

You need a fairly strong solution of the NaOH. (caustic soda chrystals) about one good tablespoon per gallon of warm water.

Carefully mix this in a container big enough to hold your bits one at a time.

Fully submerge the part and watch the bubbles form on the surface. Periodically remove the part and clean of the residue (there is a proper name for it but I can't remember it), replace in bath and repeat until you have no more dark spots. (if it does not seem to happening fast enough, you can always dissolve some more of the crystals into the solution, just be careful).

The part will now be a uniform dullish flat colour.

Rinse thouroughly with clean water and inspect, If you are not happy, then repeat the above. When you are happy, then rinse thouroughly with clean water and dry the part.

You can now sand and buff the part.

CAUTION: The part will no longer be annodized and the surface will be soft, so you will need to protect it with wax polishes or clear lacquer.

Also do a test piece first. (an old aluminium cooking pot for example)

Any chemists out there who can hopefully explain the chemical reaction, because it has been more than 25 years since I studied chemistry?

 

Translator, the chemical reaction that you are talking about is the aluminum is oxidizing (causing the discoloration since the aluminum is mixing with oxygen to make AlO2). When you mix in the crystals, you are making a basic solution of water with free sodium (Na) and hydroxide ions (OH). The sodium has a stronger attraction to the oxygen than the aluminum, which then converts the aluminum oxide back to aluminum. The bubbles you are seeing is the recombining of the hydroxide ions with each other (due to an over abundance), forming water (H2O) and the bubbles are free oxygen (O2).

If you need any more help, let me know.

 

These guys are correct. when polishing motorcycle frames which are anodized aluminium, I had the best luck with "easy off oven cleaner" A bit of additional Info, The anodizing on aluminum is one of the hardest substances on the planet. It takes a PILE of work to get through it and polish the aluminum. Quite frankly, it isn't worth the effort.

 

Superb info, yet again Thermo.

Thanks,
but any chance of the formula? (for my education) my brain is somewhat addled. have been trying to figure it out from my old Chemistry books.

1 alumin oxide + 2 sodium hydroxide + 3 waters =

Al2O3 +2NaOh + 3H20 = Should = lots of water, more sodium hydroxide, aluminium, and oxygen floating around.

So the part gets back to Aluminium, I think??

 

Translator, you have the idea. Gotta love being overly trained for your job. But, I guess that is better than having a rock running a nuclear reactor. Seen that too. Granted, some would say I was the rock as they nicknamed me "Homer". Scared? It was all in fun. They said push the limits and boy did I push the limits.

 

Well fellows, thanks for the input. I had recently given up (after many hours) of drain cleaner and yellow can of oven cleaner.
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