What kind of finish is on the aluminum bumpers?

[shanebo]

Bens gots a very good point...Aluminum and steel are electrochemically dissimilar and when they are in contact with eachother it causes a galvanic reaction which is basically the movement of ions from one metal to the other, this process is further amplified when other elements such as salt and water are thrown in the mix...the result being corrosion and deterioration of the metals.

[priya]

I tried Easy off on the bumper today as Budwisr suggested.  The instructions he sent me said to leave it on 3 to 5 minutes or it will pit the aluminum:
http://www.raydobbins.com/polishing/

I put it on and left it 5 minutes and then rubbed with steel wool and it had no effect.  I reapplied and waited 15 minutes and then I could see the part of the bumper that had already had the annodizing removed was turning black under the Easy off.  I took the steel wool to it and roughly half the anodizing came off although the part of the bumper where it had previously been removed turned black.  I pulled out my 40 grit sander and the black came off the bare aluminum fairly easily and the remainder of the anodizing sanded off with perhaps 1/3  to 1/2 the effort the untreated anodizing took to sand off. It was about 50 degrees F. in the garage so that probably accounted for some of the extra time it took for the Easy off to work. All in all I estimate I removed the anodizing treated with Easy off in about 1/4 to 1/5 the time of the untreated anodizing.  Still pretty slow but no where near the hair pulling out/screaming experience it was without the Easy off, so two thumbs up, thanks again, Budwisr for the suggestion!

[eagleman]

Thats interesting.I tried easy off on my front bumper today just to see what would happen and it seemed to work pretty well.I left it on around ten minutes and then used fine steel wool and the wool and bumper turned black.Used a clean rag and wiped it off and looks to be ready for some serious sanding.Not to bad I thought to myself so I tried it on the rear bumper and nothing and I mean nothing.Maybe I didn't leave it on long enough but will try it again tomorrow and leave it on longer.Was thinking after doing a small section on the front bumper that this ain't gonna be to bad.Now not sure but will try again.

[Budwisr]

 Glad the tip helped Priya. I think warmer temps would have helped the process. One important point when using oven cleaner, it needs to be the "old fashion" type not the newer low odor type.
 Also over the weekend I inspected my Eagles closer and all of them (5) have the aluminum bumpers. Maybe the chrome bumpers were pre '81. Also after talking to some other AMC guys, I believe the alloy used is a Zinc -Aluminum. The bumpers are very hard, most likely in order to meet the 5 mph crash requirements. I think that is why the recycle guys misidentified the metal as SS. I tried a brass key scratch test and the brass doesn't seem to touch the alloy.

[eagleman]

Maybe thats why,I used what wife had in her laundry cabinet and it was the new low odor type.Will pick up the old fashion type tomorrow and give it a go.Thanks for the heads up.

[maddog]

just don't get it on your paint because it will take it off as well. my has used this stuff to strip a car thats how i know.

[priya]

I used the regular Easy off rather than the low odour.

[priya]

Thats interesting.I tried easy off on my front bumper today just to see what would happen and it seemed to work pretty well.I left it on around ten minutes and then used fine steel wool and the wool and bumper turned black.Used a clean rag and wiped it off and looks to be ready for some serious sanding.Not to bad I thought to myself so I tried it on the rear bumper and nothing and I mean nothing.

I had a similar experience today.  I had initially used the Easy off on the side of the bumper and I hadn't touched the top of the bumper so today I sprayed the top of the bumper with Easy off, waited 15 minutes, didn't see any black, so waited another 5 and took the steel wool to it and it didn't remove any of the anodizing.  I figured I'd try sanding the top of the bumper a bit and reapplying as the spot I did on the side of the bumper had had some sanding before I put the Easy off on it.  I spent 5 or 10 minutes on the top of the bumper with 60 grit, just long enough to remove the shine, and then reapplied the easy off.  After 20 minutes I took the steel wool to it and it removed  perhaps 1/3 of the anodizing and thinned out the remainder of it a bit.  I went back with the jitterbug and the 60 grit and once again its comming off a lot faster than with no easy off, but its still pretty slow going - about 45 minutes of sanding and there's maybe 15% of the anodizing left although the bumper has slight vallies in it so the flat jitterbug takes a long time to sand down the surrounding "hills" to get to the vallies.  The anodizing is incredibly tough, the best approach might be to sand initially with 40 or 60 grit for 5 or 10 minutes, apply the easy off, clean, sand again for 5 or 10 minutes, apply easy off again and then sand again.

[eagleman]

Well then I'll try that and see how it goes! Wife went into town today so I had her pick me up a can of the regular oven cleaned and about all it did was stink up the garage.Was rather disappointed but I should have known it wouldn't be that easy. So tomorrow its back to the drawning board and I'll sand it first and try again.There is no doubt in my mind that we'll get it sooner or later.

[vangremlin]

Well then I'll try that and see how it goes! Wife went into town today so I had her pick me up a can of the regular oven cleaned and about all it did was stink up the garage.Was rather disappointed but I should have known it wouldn't be that easy. So tomorrow its back to the drawning board and I'll sand it first and try again.There is no doubt in my mind that we'll get it sooner or later.

You might look into getting them sandblasted.  I had a pair of bumpers done for $35.

[priya]

I finally got finished sanding and polishing the rear bumper.  It looks shinier in person than it does in the picture, but here's before:


And after:


Came out real nice, but I think it took me around 40 hours!  I won't be doing the front bumper.

[WoodenBirdOfPrey]

40 hours?  Holy smokes, you have dedication!  I would have walked away after the first 15 minutes and seeing how hard it was going to be.  It looks great like everything you do though!

[priya]

Thanks Woodenbirdofprey.  I guess having done a lot of bodywork in the past gets you used to tedious slow work, but this was particularly drawn out.  Once I ruined the anodizing though I figured I had to see it through so I did knowing it was going to be a long time.

[priya]

I'm going to look for that tomorrow, Casper.

[eagleman]

Don't mind the forty hours of hard work! Its the knowning what the forty hours of hard work is going to render that keeps me going. Nice work Priya!