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OK, we had a thread on polishing aluminum earlier. Here's my experiences on using different abrasive blasting media, along with one type of chemical cleaning.


What I started with were engine cases that were very heavily oxidized: white powdery aluminum corrosion:









I began with the least abrasive - walnut shells - in the blaster. My blaster is the least expensive Harbor Freight floor standing model. My compressor does not deliver enough air for continuous use. I have to pause every few minutes to let it catch up. 45 seconds of blasting, 1 minute for the compressor to pump up. :D

The walnut shells would remove SOME of the corrosion, but not all of it. Didn't really 'clean' the aluminum, either.





Next, I had been told of a product called Aluminum Jelly. I guess it's just like Naval Jelly, only for aluminum. Picked up this bottle at my local Ace Hardware for $4.



You brush it on, leave it sit for 5 minutes and hose it off. Repeat as needed for more cleaning. Don't leave it on for more than 5 minutes per application or it can discolor the aluminum black. Contains phosphoric acid, according to the bottle.





I think it did a really good job, considering how bad the corrosion was to begin with, and how easy the stuff is to use. Not 100%, though, but by the 3rd application, it had done a really nice job. This would work great, IMO, on things like wheel hubs that you don't want to de-spoke or are too large to get into a blast cabinet.

Here's a look after 3 applications:




And, just as an experiment, I went back over the Jelly'd area with walnut shells again. This time, it DID remove the last bits of corrosion. A very nice, satin finish:





But, pretty labor intensive between 3 app's of Jelly AND a trip thru the walnut shells. So, the next experiment was to use glass beads in the blast cabinet. IMHO, this worked great! One time thru, and very good results, without being as 'rough' as using sand.





To me, this was the best choice for the cases, and I wound up doing the whole job with glass beads. Using about 80 psi in the blaster.





The only downside was that bead blasting goes kinda slow compared to using sand, but it gives you a more satin, OEM look. Like pressure washing your driveway with 1000 psi washer vs. the big 3500 psi jobbies. You've got to hold the nozzle closer and go back over it to make the finish uniform. I've done sandblasting many times, and it goes much faster, but leaves a roughened surface on aluminum. It's perfect for many rougher cases, cylinder fins and cylinder heads. Also, it's great for prepping for painting, if you're going that route, but not for eventual polishing. Sand roughens the surface, making it VERY time consuming to polish to brightness later on. Here's a look at a previous job done using $3 bag of Home Depot play sand in the blaster at 100 psi. This goes very quickly and removes paint, rust, corrosion, blemishes, etc. And, because it does such a good job stripping, it is much easier to get a uniform result.





And finally, just in an effort to find something that walnut shells do well, I tried it on very heavily sun-damaged plastic side covers. As you see, the covers were VERY badly sun damaged. The kind of oxidation that scrapes off on your fingers.






Wow, did that work great! IMO, it saved these otherwise ready-for-the-trash pieces. This was done at about 50 psi:








So, there you have it. Nothing fancy, just a quick overview of some experimenting I did one day. You're experiences may vary! :)

Kirk
 

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Hey, GB, thanks.

No, never tried it yet. I have a container of it, but haven't used it. Is it more aggressive or less aggressive than sand? For some reason, I had it in my mind that it was MORE aggressive. Like for stripping heavy rust from steel. But, I don't know why I have that impression.
 

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sand blasting is way too rough for aluminium. glasbead blasting is better
the best method I've seen for cleaning aluminium and getting a nice surface finish is vapor blasting.
don't know much about the technical aspect of the process, but the results are really nice.
you can see some before/after pictures on this site:
http://www.starsonwheels.be/
 

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jiveassjeff said:
sand blasting is way too rough for aluminium. glasbead blasting is better
the best method I've seen for cleaning aluminium and getting a nice surface finish is vapor blasting.
don't know much about the technical aspect of the process, but the results are really nice.
you can see some before/after pictures on this site:
http://www.starsonwheels.be/
Those are some great before/after pics. Too bad it's not in english. I've never hear of vapor blasting so I guess I better do some research. The end results are exactly what I'm looking for.
 

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I used aluminum oxide quite a bit in a previous job, that stuff is mean. In my opinion meaner than glass beads or sand. Eastwood says it's good for paint and rust removal....I once wrote my name into a chunk of 2x4 with it, so it's pretty mean stuff, this was also at ~100psi
 

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I did'nt think aluminum oxide was that bad really. We use it at work (industrial 20x30 booth/4"hose/variable PSI) on aluminum components, and it leaves a nice sparkle finish. ;) Although that finish could be a little rougher than you guiys are looking for. If it was used on engine cases before painting then it'd be excellent. If polishing, probably not so good. In that case I think the glass bead/walnut shell would be the way to go.

Those cases are looking good though :)


GB :mrgreen:
 

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I'm going to be doing some sandblasting this weekend for the first time. If I use sand on the cases at a lower PSI will that do okay? I will be painting everything I blast. Or should I go find some beads?

As far as painting after, what prep do I have to do? Just wash the parts with water?
 

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Discussion Starter #10
If you're going to be painting the parts, then, IMO you don't need to take any particular precautions.

I've done a handfull of aluminum engine cases using sand and when painted, there were no issues whatsoever with surface roughness. Sand leaves a rougher surface than glass beads, but still suitable for cases and cylinders & heads. Not so good if you're wanting to polish the part later.

Even so, you can experiment with pressures and distance from the nozzle to the part.

As for clean up / prep, yes you'll definitely want to wash the parts in SOMEthing. Hot water and soap works well, as does ordinary parts degreasers although they can sometimes mess with the paint if there's any of THAT residue left. Blowing the part clean with compressed air is just not enough. There's still a sandy residue left that it seems that only a liquid bath will get rid of.

Have fun!
 

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I'm a big fan of crushed walnut shells. I built a blast tent in my garage and use one of the Harbor Freight blast pot things. The compressor will do "maybe" 10 cfm. Depending on the blast nozzle size I'm using, sometimes I have to let the compressor catch up. Then I suit up all hazmat style; Tyvek hooded coveralls, ear plugs, goggles, face shield, respirator and gauntleted, thin rubber gloves. Thanks to a chronic moisture in the line problem, I'm well practiced in swearin' and cussin' to myself when the blaster clogs. That problem is sorta taken care of now. I recently blasted three CB72 engines for a buddies customer and they turned out pretty good. Admittedly, they weren't as crusty as the engine in the previous picture, but the 18/40 grit walnut shells at 90-100psi made quick work of the years of accumulated crud. So much easier than the engine cleaner/toothbrush method. I shy away from using glass beads when it comes to blasting engine parts 'cause I never trust I'm gonna get all the glass outta there.
How about using the dishwasher for the final cleaning? I guess get another one for the workshop or wait till the woman of the house is out. Don't forget roses and chocolate as a back up plan. :oops:
When it comes to frames and crusty/rusty chassis bits, I go with the glass beads. I think sand is way more than is needed. Plus, you can drop down in nozzle size, resulting in less cfm required. Happy compressor.
And when I recently went through my FZ600, I used the walnut shells to remove 80-90% of the crummy old paint from the ABS plastic fairings. WAY better than sanding for hours and hours.
Nate in PDX
 

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I have to media blast my CL175 motor in the future. I'm not going to bead blast it, as much as I love the finish and how good a job it does. Anybody done a motor using soda blast? Harbor Freight has a small set up for $99 (plus $29 for a bag of soda). I believe I'm going to buy it and give it a go- cleanup is with water. No worries about glass beads getting inside the motor!

Anybody here have experience with soda blasting? :?:
 

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I'm going to be doing some soda blasting this weekend. I'll be experimenting on the carburetor shown in the first picture in this thread.

Here are a few links to some other forums and sites that give some great hints and teasers. I made one of the home-made soda blast nozzles. It works with sand, and I'll try it out with soda this evening! It sounds, from other folks' descriptions, like it works pretty well, and cleanup is a lot easier (water). And the fact that the soda dissolves in water leaves no worries about glass beads or sand getting into where it shouldn't...

More to come, I hope.

http://www.vjmog.com/ftopict-3560.html

http://forums.sohc4.net/index.php?topic=49962.0

http://www.aircooledtech.com/tools-on-t ... a_blaster/
 

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I put together the small blaster shown on the aircooledtech page. Haven't used it for soda yet. Did use it for engine cleaning. Boiled up a big pot of water. Warmed up the engine for a short time, then sprayed with Simple Green and let soak. Then took the boiled water and 90psi of air and did some cleaning. Used a cut down and somewhat flattened acid brush for in between the cooling fins.

NE
 

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Anyone have any thoughts regarding the protection of the aluminum cases/cylinder heads after soda blasting? Polishing the cases seems reasonable, but the heads? Will the freshly blasted aluminum parts corrode even after a baking soda treatment? It would be interesting to find data on long term soda blasting results.
 

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Brushes said:
Anyone have any thoughts regarding the protection of the aluminum cases/cylinder heads after soda blasting? Polishing the cases seems reasonable, but the heads? Will the freshly blasted aluminum parts corrode even after a baking soda treatment? It would be interesting to find data on long term soda blasting results.
Good questions, I wonder myself. Common sense tells me that yes, the now bare aluminum will corrode after cleaning, but I'm not too worried. But I don't think the soda has anything chemically in it's nature to speed up or cause a problem with corrosion. Anyone else have an opinion or solid experience- I'm itching to get a soda blaster as I have carb bodies, heads, and cylinders ready to try it on!
 

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I thought I'd update this thread with the results of the soda blasting. It works, sorta, but...

It did a pretty nice job, but it takes a while. Soda isn't very abrasive after all. It doesn't really do anything to that white powdery corrosion you get on aluminum, but it DOES clean it up nicely otherwise. Leaves a fairly nice finish too.

Overall, if you're going to be doing disassembly anyway, regular cleaners, parts washers, beadblasting, etc. might be better. But, for on-bike cleaning, it should do well.

Plus, the water clean-up is nice as is the fact that it dissolves in water so you have less to worry about re: sand or grit getting where it shouldn't.

Here's two quick before and after pictures of the carb shown on the first page.



 

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I'd say that soda did pretty darn good as knackered as that carb was to begin with.. Looks like it came from a recent archaeological dig in the before pic.. :p

Nice in the after pic though.. ;)


GB :mrgreen:
 

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True, true, it did a pretty nice job. But, most of the time, a carb dip will do the same. So, if you gotta dip the carb as part of a carb OH anyway (to clean the internal passages and all)....

But, yeah, the soda did a pretty fair job. And I DO like the water-based clean up. It's another tool in the toolbox... :D
 
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