Shotblasting the plastic coating?

[rpage]

Hi All,

I have finally finished the preparations required to lift the body off my S3's wounded chassis. Two young kids and a job have meant this has taken longer than planned...!!!

Anyway, I planned to have the chassis shot blasted and repainted. Someone told me yesterday that you need to scrape all the plastic coating off the metal before you have it shotblasted otherwise the shot just bounces off the plastic.

Is this true? I assumed that shotblasting would remove all the plastic and save me the job. If not, I may just scrape off as best I can and paint straight away.

Ralph

[kentishs2]

rpage said:

Hi All, I have finally finished the preparations required to lift the body off my S3's wounded chassis. Two young kids and a job have meant this has taken longer than planned...!!! Anyway, I planned to have the chassis shot blasted and repainted. Someone told me yesterday that you need to scrape all the plastic coating off the metal before you have it shotblasted otherwise the shot just bounces off the plastic. Is this true? I assumed that shotblasting would remove all the plastic and save me the job. If not, I may just scrape off as best I can and paint straight away. Ralph

IMHO, I would say that this doesn't sound very likely.
I have seen GRP panels blasted to remove the paint and gel coat and this worked very well, the person doing this work commented that you must not concentrate the blasting in one place too long as you can go through the GRP.

Painting looks smart, although I still think that a good under body sealer is best and can easily be re-applied every few years.

Bear in mind that many closed cavaties in bodywork and chassis tend to corrode from the inside out. So, whilst you are doing the outside it is worth supporting the chassis on a level set of axle stands and drilling holes in the lowest points of the chassis in each section and coat it inside with the clear waxoyl sealer, you can buy this stuff in large cans with a catheter kit for this purpose.

This will ensure that should any condensation build up inside the chassis it will drain through the hole you have drilled at the lowest point and there will also be a handy hole to access the inside of the chassis to re-apply sealer inside again in the future.

>> Edited by kentishs2 on Friday 11th June 11:38

[z_chromozone]

Blasting will remove the coating. Does it really need to be blasted, the amount of extra work required put me off. If you are going to go down that route be prepared to not have the car mobile again for a very long time.

Based upon my experince the chassis tube had not rusted from the inside out, rather water had penetrated through holes and sat in the bottom of the tubes. I personally not recommend drilling holes to fill with wax oil unless you can be confident of filling them after. Keep in mind the fact that oil based products are combustable at the temperature required to weld and that holes introduce potential sites for further rust propagation.

With most chassis I have seen damage is usually limited to the out-riggers, and the fueltank supports. Mine had also corroded below the manifolds where the heat had got to it, but not to any grat exctent. You may feel that it is enough to strip off the surface rust and paint rather than do a complete strip down. I have almost finished my project, but I should think that I have spent nearly 100 hours on it already. The whole thing seemed to snowball at one point.

Hope that you get it sorted,

Z

[Mel-S3]

Well, i was told by a guy who had just had is chassis shot blasted that the shot would NOT penetrate the powder coating. Apparently to remove it he had to burn it of with oxy acetylene. Recently I've just had my wishbones shot blasted, so when i got the quote i pointed out that they were powder coated. His reply was it would be 4 times more expensive to remove this, because it will take 4 times longer. So i also burnt it off. Maybe some shot blasting equipment is better than others, who know, this is just my experience. Better to ask when you get quotes.

[mickypee]

Part of what you say is correct,when a powdercoated item is blasted,it can be difficult to remove if it has been put on properly!! If on the other hand we are talking about TVR's powdercoat,it's no problem,they probably won't have been blasted(although I have recently had 4 wishbones for the griff which had been blasted,phosphoric etched and coated,net result it wouldn't easily blast.I think they are doing it properly these days-about time)I have recently shotblasted the Griff chassis, then had it Zink powder primed and then polyester powdercoated satin black.A fantastic job all for £250 + VAT.Company is in High Wycombe and turned it round in 3 days.I couldn't recomend them highly enough.

Have a look:
www.jeepwrangler.fsnet.co.uk/id45.htm

Will be doing the S chassis shortly.

[rpage]

Mickypee, would you mind telling me the shotblasting company you used. I am in Reading so it should be easy for me to get to them.

Ralph

[mickypee]

I have sent you the details of the powdercoat company to you email address.Hope all goes well.

[kev s3]

already been down this road with mine, finished a total body off and strip down start of april. the guy that shotblasted mine said it would be taked off but it would take a lot longer to blast. so i stripped mine off first. tried loads of methods, heat wire brushes etc. then tried nitromorse, the plastic virtually dripped off think this saved a load of money at the balasters to. also got my welding donr b4 it was shotbalsted. if u need any more info let me know.
cheers

oh if u use the nitromorse allow it time to work, paint an area and leave it for about 15 mins, it lets off some pretty bad fumes with this plastic coating so get yourself an organic particle resperator. around a tenner from places like alison gray etc. well worth the money! cheers

>> Edited by kev s3 on Saturday 12th June 10:28

[phil dicky]

Be very careful with the shot blasting route, I own a shot blasting company and its very specialised. As regards the coating I personaly wouldn't blast this. Anthing with a rubber compound in it will bounce the blast media. If you conscentrate for longer to remove it you risk damaging the chassis. Make sure you use a company recomended which I'm sure you would do anyway.

Phil

[phil dicky]

Be very careful with the shot blasting route, I own a shot blasting company and its very specialised. As regards the coating I personaly wouldn't blast this. Anthing with a rubber compound in it will bounce the blast media. If you conscentrate for longer to remove it you risk damaging the chassis. Make sure you use a company recomended which I'm sure you would do anyway.

Phil