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Post by RGR 60130 on Dec 26, 2011 22:14:29 GMT
While I am making and fitting a new body to my Class 5 tender, I want to re-paint the chassis. To make a decent job of it will require the old paint to be stripped off. After a bit of research, it looks like Soda Blasting might be the perfect solution.
Apparently it can cope with traces of oil and won't damage the bearing surfaces. Has anyone actually tried it in this application and was it successful?
Reg
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Smifffy
Statesman
Rock'n'Roll!
Posts: 943
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Post by Smifffy on Dec 26, 2011 22:45:52 GMT
Hi Reg,
One of the chaps at my club has spoken about doing this. Whether or not he has yet, I don't know, but will ask him on Thurs eve.
Smifffy
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Smifffy
Statesman
Rock'n'Roll!
Posts: 943
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Post by Smifffy on Dec 26, 2011 22:50:11 GMT
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springbok
Statesman
Building a Thompson Class B1 in 5"g Plus restoring a 3" Fowler steam road Engine "The Wanderer".
Posts: 570
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Post by springbok on Dec 27, 2011 3:24:31 GMT
Smiffy
Very interesting would like to hear more as have some tender frames to clean up
Bob
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Post by johnkeates on Dec 31, 2011 11:18:57 GMT
Hi Reg
I don't have any experience with soda blasting but glass bead blasting will do a perfect job without damaging bearing surfaces if it is done carefully. I am a very satisfied customer!
John Keates
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Post by GWRdriver on Dec 31, 2011 16:58:07 GMT
Reg,
Yes, I have used soda blasting recently. First I'll have to say that as with any such service the results one gets will be to a great extent dependent upon the abilities of operator, but generally I was very pleased with my results. I am restoring a 1960s era Rockwell 15" drill press, very similar in size and purpose to the old Fobco Stars, with several layers of caked on paint with an oily accumulation on many surfaces. I took the bare head and base castings to a local abrasive blasting service who recommended soda and that I wouldn't have to bother with masking off. I must say I was extremely pleased with the results. Not only did the soda remove everything on the surfaces it left the machined surfaces looking untouched. I think a distinction should be made between machined and ground or otherwise finely finished surfaces. All of the surfaces I had to contend with were either as-cast or production machined. I don't think it would be reasonable to expect a ground or polished finish to emerge from this treatment looking as if they hadn't been touched.
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Post by chris595959 on Jan 1, 2012 17:15:47 GMT
When Soda blasting is used it generally does a good job, but it also has a residual problem, the Bicarbonate of Soda with a Ph of 7.5 (slightly alkaline) becomes something much more aggressive with a Ph of 9.5 when the temperature increases. So on a nice hot day your paint will be quietly pickling away at the seams and overlaps. Soda blasting will remove paint, but not corrosion.
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springbok
Statesman
Building a Thompson Class B1 in 5"g Plus restoring a 3" Fowler steam road Engine "The Wanderer".
Posts: 570
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Post by springbok on Jan 2, 2012 3:07:56 GMT
Chris
I am no chemist by any stretch of the imagination, when the good lady says whilst you are going to the village get me some asperin and they start asking Qs I blank out so thank you for that but still trying to clean up my tender frames which after a lot of years of hard use need some TLC so what would you reccomend. I live out in the country so popping out to the nearest.... is like a day trip. I have to say that in the video it was only used on wood and that would then have been covered by a wax or oil substance. I do not want to go down the road of purchasing a bit of kit that I will only use once. Do car bodyshop repair units have metal cleaning facilities. Throwing ideas
Bob
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Post by chris595959 on Jan 2, 2012 8:46:15 GMT
A lot of vehicle restorers use dry plastic media .This blast cleaning technique uses millions of tiny particles of angular graded plastic propelled at the surface to be paint stripped in a stream of fast moving compressed air. It will remove the paint with no damage to the metal underneath
Chris
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Post by tombayford on Jan 2, 2012 10:49:24 GMT
A lot of vehicle restorers use dry plastic media .This blast cleaning technique uses millions of tiny particles of angular graded plastic propelled at the surface to be paint stripped in a stream of fast moving compressed air. It will remove the paint with no damage to the metal underneath Chris We used to sell that stuff at my last company for aircraft paint removal used to come in 20 kg's boxes |
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Post by Roger on Jan 31, 2014 9:32:10 GMT
When Soda blasting is used it generally does a good job, but it also has a residual problem, the Bicarbonate of Soda with a Ph of 7.5 (slightly alkaline) becomes something much more aggressive with a Ph of 9.5 when the temperature increases. So on a nice hot day your paint will be quietly pickling away at the seams and overlaps. Soda blasting will remove paint, but not corrosion. That begs the question, what happens when you use an acid etch primer after Soda blasting? It seems to me that the Ph of the Soda is very slight and ought to be neutralised easily by the etch primer? I can't find any information about he Ph of etch primers. Is there a Chemist in the house who can get to the bottom of this? Roger |
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Post by andyhigham on Jan 31, 2014 20:27:02 GMT
For paint stripping I swear by these people www.paint-strip.co.uk/Even manky, oily, painted motorcycle engine cases come out clean and ready for re painting |
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jma1009
Elder Statesman
Posts: 5,923
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Post by jma1009 on Feb 1, 2014 0:03:56 GMT
hi Reg,
when ive rebuilt locos its a case of removing all the removable bits and scraping off all the old paint and cleaning thoroughly with cellulose thinner. i dont think there are any short cuts to what is quite a messy time consuming and laborious job.
cheers,
julian
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Post by Deleted on Feb 1, 2014 0:37:51 GMT
Hello all---------- ROGER (and others) with Soda Blast concerns about the Ph levels, then have a look and read-up on DRY ICE BLASTING >>>>>>>>>>>> en.wikipedia.org/wiki/Dry-ice_blasting ----------- JULIAN, no short cuts here just the modern way ( and that coming from a "Loctite Luddite" as well !!).... |
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Post by Roger on Feb 1, 2014 7:48:12 GMT
Hello all---------- ROGER (and others) with Soda Blast concerns about the Ph levels, then have a look and read-up on DRY ICE BLASTING >>>>>>>>>>>> en.wikipedia.org/wiki/Dry-ice_blasting ----------- JULIAN, no short cuts here just the modern way ( and that coming from a "Loctite Luddite" as well !!).... That's a clever idea, and great where you don't want any residue. To be honest, I'm of the opinion that too much is being made of the Ph levels post Soda Blasting, I doubt if you would go from blaster to spray gun without some form of a solvent wash which presumably would remove any residue. The motivation for some sort of blasting is not one of a short cut, but of getting a better key on surfaces that are known to be less keen on taking paint. Brass is the one that comes to mind, but I would have thought that a blasted finish would provide a better key for paint on any surface. Roger |
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Post by Roger on Feb 2, 2014 20:01:10 GMT
I couldn't resist having a go at designing one of these, so here's my attempt which is currently being made. All in stainless steel so it's tough and won't corrode from moisture in the compressed air. The stub on the right is 1/4" BSP which screws into a gun I already have and that holds the body in place. The body has an M8 hole where the Soda feed pipe goes in, and that can be in any orientation. The red central part has a 7mm hex machine on it near the nose so a long series socket can screw it in. The Blue nozzle is held in with an M20 thread. The hole in the red lance is 2.5mm while the hole in the blue nozzle is 3mm. The larger 4mm inside diameter to the threaded end of the red lance is just for ease of manufacture. It's all a complete guess so it will be interesting to see if it works or not. Watch this space. Roger  |
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Post by runner42 on Feb 2, 2014 21:01:09 GMT
Roger very interesting. Do you need to control the mixture of soda and air or is this an unnecessary refinement? I suppose if you are able to move the cones relative to each other that would increase decrease the amount of soda being applied. By the way what form is the soda in and is it a specially prepared soda? What air pressure do you think would you require?
Brian
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Post by Roger on Feb 2, 2014 22:06:31 GMT
Roger very interesting. Do you need to control the mixture of soda and air or is this an unnecessary refinement? I suppose if you are able to move the cones relative to each other that would increase decrease the amount of soda being applied. By the way what form is the soda in and is it a specially prepared soda? What air pressure do you think would you require? Brian You're waaaaaaaay ahead of me Brian, I've not set eyes on any soda and it's one of those 'it looks about right to me' designs. I was thinking that I could alter the size of the inlet hose and maybe the nozzle diameter but yes, I guess the clearances of the tapers could change too. It's just a bit of fun really, I'll just see what happens when I get some soda and give it a go. I'll use 100PSI since that's what the compressor is set to. Roger |
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Post by runner42 on Feb 3, 2014 6:31:48 GMT
Roger, sorry to be premature in asking questions, just my enthusiasm to see your progress. I looked again at the wikipedia link referenced above and noticed that it stated:
A sodablaster differs from a sand blaster in that the sodablaster is a direct pressure system, not gravity-fed. The blast media is directly forced out of the pressure vessel, not introduced into a stream of compressed air.
I assume that the soda has to be delivered this way to make it effective.
Brian
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Post by Roger on Feb 3, 2014 7:51:06 GMT
Roger, sorry to be premature in asking questions, just my enthusiasm to see your progress. I looked again at the wikipedia link referenced above and noticed that it stated: A sodablaster differs from a sand blaster in that the sodablaster is a direct pressure system, not gravity-fed. The blast media is directly forced out of the pressure vessel, not introduced into a stream of compressed air.
I assume that the soda has to be delivered this way to make it effective. Brian Hi Brian, No problem, I'm pleased that you're interested. That quote is at odds with what I've seen on YouTube where they just rig up a hose into a bucket of the Soda and suck it up like that. There are commercial units too that do that, and I've also seen ones with a gravity feed chamber on the top of the gun, like some paint sprayers. That's the reason I chose to make the body of it such that it's retained in place by the central lance. I thought it would be easier to add a top feeding reservoir if I could just spin it round to put the feed hole at the top. I've just checked out the Wikipedia entry and there's no citation for that 'fact' so I've deleted it. You can't always believe everything that's in Wikipedia unless there's a citation to justify the comment. I think this is someone's uninformed opinion. Roger |
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