Cleaning aluminum castings?

[Shvegel]

My engine ran great when I pulled it but in the process of the restoration I want to clean it up to a show level.  I really have 2 questions.  The first is what is the best way to clean the castings?  I used acid when I rebuilt the engine years ago and that worked pretty well but I am wondering if there is something better?  The second: Is there any way to keep the aluminum from corroding up again?  I assume mat powdercoating would be verboten in a serious show.

[Pinder]

I tried acid and it works sort of (used aluminum wheel cleaner. But it still did not look so great. i then went to Harbor freifht and bought a sand blaster. its a cheap one for use outside. I used aluminun oxide to blast it. It is messy business but cleans very fast. after its done it has a very grey look to it.  Cleaning it after blasing with brass brushes gives it a nice sheen.  I did this on both my valve cover and intake manifold. see pics attached. i think it came out nice.  I think maybe try soda blasting first ?

[Garry]

I had my rocker and inlets peened/blasted with a fine grain walnut shell and it came out well.  I have not put anything on it and after three years it is holding up well with only minor change in appearance.  Photo is shortly after getting it all back together.

[Shvegel]

They both look great.  Now I just have to build a 24' workbench in my garage and it's time to get started.

[mdsalemi]

While the peening works well, in the hands of someone who knows what they are doing and with the right abrasive, that still falls into the "mechanical" cleaning category.
Those of you who tried "acid"; which kind did you use? There are, in the USA, a variety of acid cleaners made specifically for aluminum, and they are from a variety of sources and manufacturers. Here's one:
http://www.ankosales.com/aluminum-brightener.html

If you are outside the USA, look for the contents to include varying degrees of either Hydrofluoric Acid, or Ammonium Biflouride, along with either Phosphoric, Sulfuric or Hydrochloric. The Hydrofluoric is the acid that actually does most of the work; the Ammonium Biflouride turns into that upon use. The others are there to keep the pH lo, and also to provide a sensation should you get this nasty stuff on your skin. You won't feel HF, and it will go through your skin and to your bones. Did I mention you need to take precautions with use?

http://www.sc.edu/ehs/HF/USC-HF.pdf

Most of the readily available professional aluminum brighteners used with the proper precautions will do a great job. Some consumer-level products don't work as well as they are diluted or don't contain the right ingredients.

[scoot]

Try oven cleaner.  That's what Kent Bergma uses and I tried it on a valve cover and it worked well.

[Pinder]

I tried oven cleaner on some parts and it made some parts turn black. think it works on some but I created more worn on some parts so be careful and also its a corrosive. The wall nut shells i think are the least abbrasive. from the pics above I would go with that in the media blaster and they are also non toxic so you can do it outside on the lawn.

[mdsalemi]

I tried oven cleaner on some parts and it made some parts turn black.

Every can of oven cleaner I've got--and that's plenty--always says "Do Not Use on Aluminum" or something similar. Is there some part of that statement from the product manufacturer that people don't understand?
Oven cleaner is hi-pH corrosive Sodium Hydroxide or Lye. It's meant to break down the caked on and baked on grease on steel or enamel surfaces. It will damage aluminum, that's why they tell you not to use it. Do a search for "Oven cleaner on aluminum" before you try it...there are quite a few horror stories out there where well-intentioned shade tree mechanics use it on some auto or motorcycle part with less than pleasant results.

There are plenty of purpose designed aluminum cleaners and brighteners out there, readily available, so why would you use something specifically contra-indicated?