Cleaning aluminum

[Spikedog08]

So I have many parts on my engine that are aluminum including the radiator, brackets and thermostat housing and some are stained .  I can clean with metal polish but the stains remain.  Who has the solution?   . .

[dodj]

I used this on badly stained aluminium slot wheels and they came out nice?
https://www.amazon.com/Blue-Magic-400-Ounce-Polish/dp/B000BO8Z9I

[headejm]

I copied this "recipe" to clean an aluminum bowel. Haven't tried it yet. Might work for you? Worth a try.

[MoparLeo]

Unless it is polished, it will be extremely porous like a sponge and the stains will go deep down. Even if you use some type of cleaner to get the stains out, unless the aluminum is sealed somehow. The staining will just come back. That is the purpose of anodizing on aluminum. To seal the surface.
Powder coating, polishing, are other options. etc

[tparker]

I have looked into this a bit and what I was looking for is something like Alumi-Brite or similar products. It is like an acid. I couldn't find any locally so I didn't try it yet. No where locally has it. Some marine shops might have it for cleaning aluminum boats. I tried some aluminum wheel cleaner I think and it kinda work, but didn't get all the stain out. I used it on an old edelbrock manifold

[torredcuda]

You probably need a cleaner not just a polish, some have a mild acid in them or make your own with vinegar, just make sure it does not have an anodized coating on it. Some will dull it and you`ll need to polish afterwards.

[Racer57]

You will never stop cleaning aluminum. You will need to either anodize or powder coat.  However with powder coating it will give the aluminum a gray color.

[gzig5]

Google Vapor Blasting or Vapor Honing services in your area.  Its a wet blasting process that gets aluminum insanely clean.  Used a lot on delicate carburetor parts.  It's not real cheap but as far as I am aware is the most precise way to get complicated surfaces really clean. 
One example of many available online  https://vaporhoningtechnologies.com/vapour-blasting-motorcycle-engine-parts/

[moparroy]

You will never stop cleaning aluminum. You will need to either anodize or powder coat.  However with powder coating it will give the aluminum a gray color.

I polished the valve cover on my '85 Daytona a long long time ago. The attached pic is probably half as many years old (tells me I need to clean the engine again LOL) Now the valve cover was clear coated before I polished it but I don't think it was perfect under the clear. I would have used a kind of acid polish and extra fine steel wool. I did not coat it with anything after. I do polish it by hand with metal polish once or twice a year. Still looks great (back side under the intercooler is a bit less so). I did a similar process with the valve covers for the Cuda project last year - don't have any pics here.

[Filthy Filbert]

If we're talking about as-cast raw castings... they're gonna be like a sponge and suck up everything.  Top it off with the fact that aluminum oxides faster than any other metal...

You're gonna have to sand it all smooth, then polish it.   Or, hit with a heavy degreaser and cover it with a paint that nearly matches "as-cast aluminum"

[Spikedog08]

Some good ideas here!