Cleaning up a aluminium engine block

[Walter_23]

Hi all,
I'm looking for some advice on how to clean and paint again an aluminium engine block (close up photo of a couple of pieces attached): it seems oxidized (is it oxidized? Not sure what the white stains are).
Project is to make a showcase piece.

To clean it I'm thinking about using:
- first pass: Gunk 6868 5L Ultra Engine Degreaser
- second pass: White spirit
Good idea?

To repaint:
- I would like to avoid sandblasting or vapour blasting it (too expensive), so: would the paint stick to the stained aluminium as per photos?
Any advice it would be really appreciated!

Thanks,
Walter

[ChrisJC]

The white stuff is aluminium oxide. Gunk etc. won't move it - you need a mechanical method - wire brush, or media blasting.

Chris.

[Walter_23]

Thank you Chris!
Do you know if it's advisable to paint on top of the oxide? I don't mind it to still be there, if it does not "come back up" from below the paint after few years...The main doubt is whether the paint will stick.

[stevieturbo]

Unless it's for a concourse or something, just clean as best you can, as said, wire brushes, abrasives, etc etc, perhaps a mild acid/strong wheel cleaner type product.

Then just paint away. If some comes off, big deal, throw some more paint on it.

I'd be inclined to use something you can easily brush on and touch up, as opposed to trying to be fancy and spraying

[Walter_23]

Thanks,
I see your point in trying to clean it and then paint it.

Any suggestion for an aluminium deoxidizer or any other product people hare have used with success?

Thanks!
Walter

[Ian Anderson]

How about a pressure washer?
Ian

[scudderfish]

Aluminium always has a layer of aluminium oxide on it, pretty much as soon as it is exposed to air. Unlike rust, it is stable and doesn't grow/corrode the metal.

[ChrisJC]

Aluminium does oxidise on contact with air, in about 10 seconds. However, the white flaky stuff is also aluminium oxide (I guess a different form). If you paint it, the paint will stick to the white stuff and it will all fall off.

Aluminium is very reactive, so you would need something even more reactive to remove the oxygen chemically.

I would go for mechanical means, then paint it if you wish to.

Chris.

[Walter_23]

Very useful comments,
I definitely need the paint to stick to it, and to stick well. So media blasting seems the way (no one is suggesting a deoxidizer...).

I have a homemade sandblaster that I may test (perhaps too hash on aluminium?). I got a quote to vapour blast (more gentle than pure sandblasting?) all the 9 piece of the engine (including the engine block) for £200 (no idea if it's a good price or not).

[stevieturbo]

How long will you spend trying to clean ? how much is your time worth for £200 ?


Although bare in mind any type of media blasting uses grit media......so make sure the block is thoroughly clean before building. Especially oil galleries.

A lot of engine/machine shops will have sort of hot/caustic dip tank, maybe try asking around for that ?

Or various videos on youtube for similar and DIY methods if you could be bothered with the effort.

Often it's easier just to pay someone who does that sort of thing all the time

[Ian Anderson]

Instead of sand blasting try soda blasting instead….. same thing but bicarbonate of soda which is less harsh than sand. Also dissolves and washes away in water

Ian

[Mc Tool]

Preparation is the key to a good looking job. I know it's either expensive or a pain in the arse but I can tell you that you will regret doing a half arsed job as that's what it will look like .
If you go for bead or sand blasting ......I would figure out a way to plug all the holes you don't want filled with media. Corks , bolts duct tape and budget roof sealant ( it comes off easily ).
I am just going thru this right now and this is my 2nd go as I didn't prep things properly . This time I'm also removing casting flash and smoothing off some rough bits .
Just finished polishing my efi manifold and plenum .....wore my fingertips off. Ebay China is your friend when it comes to bulk buying wire wheels ,sanding drums and scotch bright wheels for the Dremel .
Beads and sand/grit is coitusing hard to get out of threaded holes so it's worth going to the trouble to block the holes 1st