Bead blasting

[Richard]

Has anyone tried/considered baking soda?

I only mention it having seen a Barracuda bodyshell soda blasted in the second series of 'Rides'. It seemed to get all the paint off with no damage to the bodyshell.

It might be worth considering as it would dissolve in water when washing the parts afterwards.

 

This may be controversial but...stick it in the dishwasher!

 

[Russ Noble]

Thank you, gentlemen, the quality of advice is as usual - excellent.
So, aluminium oxide is definitely out. My gearbox rebuilder should be able to help with cosmetic cleaning, possibly with walnut shells as suggested here.
I shall try to stay with the baked paint option, to give as durable an external surface as possible.
Further reports once the casings have been stripped and cleaned.

Just resurrecting this old thread.

So what did you wind up doing Tony?

 

[Jim S.]

Since Russ resurrected this I thought I would just mention that Caterpillar heavy equipment company uses Baking Soda blast to clean there engine parts in there engine remanufacturing department. When the soda mixes with oil residue it turns into a soap by product. They simply blow the parts off when there down and don't worry about any light residue that's left over. They obviously wouldn't use this if it caused problems, they have a great reputation to protect.

I would probably still wash it with a good soapy water solution

Just my 2 cents

 

[Jac Mac]

Can recommend the Baking Soda blast system, a careful operator can remove the top coat or colour layers of a multi coat paint job leaving the primer base intact if in good order- engine blocks come up like they are fresh out of the core box in the foundry, virtually no effect on machined or honed surfaces, and leaves any oil in the pores of the cast iron so that surface rusting after cleaning is not a major problem. Wont remove hard long term rust concentrations and will damage cam bearings etc.

A blow over with clean air would suffice but we ussually just blow it down with air only ( no media/Baking Soda ) then give it a final hot soapy water scrub etc prior to assy.

Relatively expensive but quick- I just used to load the ute up & let them do it alongside a bigger job like truck chassis etc.

Jac Mac

 

[Tony Hunt]

Just resurrecting this old thread.

So what did you wind up doing Tony?

It was such a long time ago..............!
I think I eventually went with bead to polish the outside, avoiding having to paint, and walnut shells to finish.
The box has been in for 2 years now with no problem. The only thing is the joining bolts have gone rusty.

Tony

 

[Russ Noble]

Thanks Tony,

I've tried numerous cleaners, solvents, acids and aluminas. Both hot and cold to no real effect to try and remove darker speckles all over the outside. At this point I am seriously leaning towards plastic media blasting. Just got to do a bit more research.

Has anyone tried this?

Anyone got any experience with baking soda on corrosion blemished aluminium? That's a bit different to removing paint or cleaning off varnish and crud from engine parts.

Cheers,

 

[Steve]

I just had a 930 box soda blasted (externally only) the chaps masked and plugged everything meticulously, the case came up not like new, but very acceptable.

they insisted that the old bearings etc were all left in situ to help protect any bearing surfaces
After this they disassembled the trans, all the components went through the engine block washer and steam wash

They would not touch the inside of the trans though......said it would be asking for trouble to blast anything when it would easily clean up with a detergent or solvent wash, which they did.

Porsche trans builder then replaced the bearings ans a couple of gears, and was very happy with the condition of the box

 

[JohnC]

I've tried numerous cleaners, solvents, acids and aluminas. Both hot and cold to no real effect to try and remove darker speckles all over the outside. At this point I am seriously leaning towards plastic media blasting. Just got to do a bit more research.

Russ, I've had the same experience as you, trying to clean up cast aluminum with various chemicals, etc. And it seemed the more chemicals I tried, the darker the aluminum got.

I finally threw in the towel and had the parts glass beaded and they came out superb, and looked freshly cast. All the usual caveats apply, ie making sure the parts are well cleaned up afterward, no glass beads lurking in the cracks & crevices, etc.

Now, whenever I want that freshly cast look, I don't even waste time with the chemicals, but head straight for the glass beader. I don't mask the gasket surfaces either, and haven't had any leakage problems whatsoever.

 

[John Fitzpatrick]

Back in the '70s, my employer sent me to the Mobil Oil paint school in Houston, and one of the things that stayed with me from the one week course was a series of micrographs of surfaces blasted at different pressures by various media. The most striking was a "white blast" (100% of surface) using silica. The surface looked like a tangled mass of crab legs, and the instructor emphasized that the sharp points would protrude through a coating and rust stains would start appearing in a few months.
There's a big difference in methods and media between blasting to remove rust and blasting to prep a surface for paint.

 

[Dave P]

I recently tried to rebuild some vintage brake calipers for a friend and found that due to a simple misjudgment he had blasted his calipers with the pistons extended. It ruined the pistons and he faced having them duplicated at a very high cost. I would use extreme caution

 

[Russ Noble]

Thanks for all the replies guys.

I think the options come down to plastic, walnut, or soda as these appear to be the only media that don't embed themselves in the case. Of these, plastic appears to be the most aggressive, (you can get various types) and soda the least. The condition of my case will probably mean that plastic will be the best choice.

I will post before and after photos for anyone else wanting to go down this track.

Cheers