Aluminium Oxide 'Residue'?

[aqueous]

Hi all,

I have recently started restoring a Spitfire and found this site - brilliant forum with loads of useful info, already helped me no-end so thanks to all!

Having trawled the forums for advice on blasting, I have gone with the much recommended 20 gallon eBay blast pot, combined with a home made filing 'blast' cabinet. Works great, however I've recently started using alu oxide for the pot as everyone seems to recommend it as a 'good for all' medium, and is better for rust than glass, but I notice a sort of 'residue' that is left behind on the metal I blast with it (mostly steel).

I never had this problem with glass grit which brings it up good and shiny, and the alu oxide seems to leave it a dusty matt grey which can be wiped off with a finger - not great for then painting over.

Is this normal, and should I then use something else to clean this off? I've seen a few posts that recommend then blasting with glass, but that seems to defeat the point of using alu oxide in the first place. Is there something else I can do to prep pieces for painting?

Thanks for reading, and thanks in advance!

 

[rtbcomp]

Welcome to the forum!

Slighty off topic, but you say "glass grit which brings it up good and shiny". Sounds like you mean glass beads rather than glass grit, which leaves a rough matt surface suitable for painting.

Beads are used to give a pleasing finish, or prior to polishing, usually on ally.

 

[tigler]

The residue will be Ali oxide dust, unavoidable with that media. You would need to remove it before painting or it will react with the steel over time.
Restoration of a Spitfire has to be the ultimate project, please let us have some pix and details of the plane !!

 

[rtbcomp]

Can we clear another point - Supermarine Spitfire or Triumph Spitfire ?

 

[aqueous]

Thanks guys, yep I did mean glass beads RTB, and I'm afraid I meant the lowly Triumph type Tigler, sorry!

That said I am an aerospace engineer by trade and I completely agree, restoring a Supermarine has to be the ultimate challenge - I fully intend to do one before my time is up, but that will have to wait until I have more time/money/hangar space! I think the going rate for a Spit restore is currently £300k and climbing, but you can still get loads of the bits on eBay!

Back on the topic, the oxide dust does come off easily enough with petrol and a stiff brush, but I worry that it looks like the kind of stuff that will impregante itself in the metal and muck up a paint job. Will a stiff scrub be enough?

 

[rtbcomp]

Thanks guys, yep I did mean glass beads RTB, ....... Will a stiff scrub be enough?

Glass beads are the wrong stuff to use then, and very expensive.

You could always blast the residue off with grit

 

[tigler]

LOL !! I didn't even think it was more likely to be a Triumph Spitfire !! Ah well !!

 

[graffian]

Blow the dust off then wash with brake cleaner.

 

[rtbcomp]

Or you could wash with a thinner compatible with the paint you're going to use.