Salt on aluminum

[scottiec]

Hi Guys,

I am sweaty greasy Italian. Working on the car, I have managed to sweat on the aluminum panels. The salt from my sweat has practically damaged the panels. Some cutting compound with elbow grease gets rid of some of it, but not completely. I tried a small area with scotchbrite, which works. However, it dulls the panel and really scratches it up.

EDIT: Also tried brake clean. no go.

Any advice?

Scottie

[DaveS53]

Trying to maintain the as-received finish on aluminum sheet metal is hopeless. I have a lot of aluminum panels on my car. I gave them all a brushed finish that can be maintained without much difficulty. Start by sanding with 120 grit, then 220, then 400 and finally use maroon scotchbrite for the final finish. Most minor scratches that occur later can be touched up just with scotchbrite. I did all of my sanding in the vertical direction.

[NAZ]

That's patina and some folks like the look of weathered aluminum. Solvents won't remove the oxide and as you have found, it goes deep into the metal. Scotchbrite will work but is very aggressive and if you want the panels to be somewhat glossy you'll have to sand with some extremely fine sand paper before polishing out the fine scratches. Take it from someone that has polished a lot of aluminum -- that's a ton of work.

You can use chemical products that clean the aluminum by etching to brighten it up at bit. Sharkhide and Eastwood make products for this but be VERY careful as these contain hydrofluoric acid which is about the most dangerous acid you will ever use. I can't overstate the need to wear proper PPE when using these products and you should have a running water hose near the work area as any acid contacting your skin is an emergency that requires immediately flushing the affected area, especially if it's hydrofluoric acid. The panels should also be free of oil and wax before applying these chemical cleaners or the panels will look splotchy. Leave it on too long it it will get very dull from being over etched. These chemical cleaners take a lot of the work out cleaning oxidized aluminum but must be respected. Of course you could always paint or powder coat the panels and that will protect them from further staining or oxidization.

[scottiec]

Trying to maintain the as-received finish on aluminum sheet metal is hopeless. I have a lot of aluminum panels on my car. I gave them all a brushed finish that can be maintained without much difficulty. Start by sanding with 120 grit, then 220, then 400 and finally use maroon scotchbrite for the final finish. Most minor scratches that occur later can be touched up just with scotchbrite. I did all of my sanding in the vertical direction.

I used the maroon scotchbrite on it to start. Is there a way to get a shine out of that look? I am not too particular about it, just curious.

[scottiec]

That's patina and some folks like the look of weathered aluminum. Solvents won't remove the oxide and as you have found, it goes deep into the metal. Scotchbrite will work but is very aggressive and if you want the panels to be somewhat glossy you'll have to sand with some extremely fine sand paper before polishing out the fine scratches. Take it from someone that has polished a lot of aluminum -- that's a ton of work.

You can use chemical products that clean the aluminum by etching to brighten it up at bit. Sharkhide and Eastwood make products for this but be VERY careful as these contain hydrofluoric acid which is about the most dangerous acid you will ever use. I can't overstate the need to wear proper PPE when using these products and you should have a running water hose near the work area as any acid contacting your skin is an emergency that requires immediately flushing the affected area, especially if it's hydrofluoric acid. The panels should also be free of oil and wax before applying these chemical cleaners or the panels will look splotchy. Leave it on too long it it will get very dull from being over etched. These chemical cleaners take a lot of the work out cleaning oxidized aluminum but must be respected. Of course you could always paint or powder coat the panels and that will protect them from further staining or oxidization.

Wow. I had no idea. I'll stick with the patina and give elbow grease where I can. Or I can sweat more on them and it will be consistent hahaha

[DaveS53]

I used the maroon scotchbrite on it to start. Is there a way to get a shine out of that look? I am not too particular about it, just curious.

The problem is that most aluminum sheet metal has a thin layer that is cold-worked and until that is removed by sanding or coarse polishing, there is no way to create a uniform finish. When I sanded my panels, you could tell that there were darker areas where I had not sanded through the cold-worked layer. Lighter colored areas show as the cold-work is removed. "Shiny" requires a lot finer grit than scotchbrite. I have a 1hp buffer that I used to polish some aluminum parts, but I decided that it was way too much work to polish a large aluminum panel.

[PeteH]

you can use polishing compound and hand rub. I've seen Lemon Pledge used on polished aluminum to maintain it.

[scottiec]

Thanks so much guys. I appreciate the info and pictures!

[NAZ]

Speaking of Pledge -- it works great to remove bugs. We use it on our SAR aircraft as flying low you get lots of bugs build up on the leading edges of wings and such.

I'm with Dave on polishing large panels and trying to make them look uniform -- no way I'm going that route, ever! Way too much work. As for protecting bare aluminum, I've had good luck with Sharkhide. It's a bit expensive but lasts a long time and will help prevent staining on a natural finish. But powder coat is the easiest to care for.

[Svtfreak]

I wiped a little wd40 after install and clean up and they aren't developing those spots. I'm sure they will in time though.

[RoadRacer]

That's patina

Amen. Drive it like you hate it