Soda blasting or acid dipping

[Murrayminor]

Hi all
My '65 2 door is now a bare shell and I'm at a position to begin some bodywork.
Looking at the underneath I can clearly see its been liberally coated with horrible underseal, in order to access the condition of the bodyshell I was thinking of having the shell either acid dipped or soda blasted.
Has anyone any ideas on which would be the better process?
I attempted to remove some of the underseal with a wire wheel on my angle grinder but even the light coating I started on made a horrible mess so the thicker stuff would be a nightmare to remove hence the question.
Regards
Dermot.

[pgp001]

Not sure about acid dipping, but blasting will probably not work very well on soft sticky materials, the blasting media will just become embedded into it.

Phil

[Steve Phillips]

SPL are probably the best know company for acid dipping, although there is probably others out there, they can quote you and explain much more about it than I can,

You say soda blasting, you will find a lot of companies use the word "soda" some in their blurb, some even in the company name, but most use crushed glass,

Glass is not as aggressive as chilled iron "shot blasting" which will distort the work piece, but is perfectly capable of removing paint, rust and some underseal, although it's not aggressive enough to remove heavy rubber based underseal, typically glass is used at around 40psi, where as shot blasting is used around 100psi,

Soda is so gentle that all it will remove is paint, but any rust or underseal would still need removing with glass or chilled iron if it's really on there, soda is also very expensive compared to glass and shot ""chilled iron"

Hope that helps,

Steve

[don58van]

MurrayMinor

I agree that blasting is unsuitable. I don't know whether acid dipping takes underseal off.

If its original (factory) underseal, it will probably be fairly dry and hard. I used a scraper to kind-of chip the underseal off my '70 model. I used a very narrow scraper to get enough force onto the edge of the sealer to dislodge it. It is best to slightly round off the corners of the scraper so that it doesn't gouge the metal.

It is very messy, but paint stripper helps to soften underseal to make it easier to scrape off rather chip off (might depend on the active ingredient in the stripper).

I found white spirits on a rag excellent for cleaning up residual sealer.

Don

[midget]

Diesel fuel will soften underseal and make this very messy job easier. I have tried all other options, without success.
Aggressive grit blasting at "commercial" pressure will work faster, but causes unwanted damage to structure and is expensive.

[Steve Phillips]

Wasn’t saying blasting is unsuitable, just pointing out the differences, Glass is probably the most common method used now, but Soda has become the “in” word, and some companies will charge soda prices and use glass, (which is much cheaper)

if you do present a vehicle for any sort of blasting other than shot blasting then unfortunately you will need to remove a lot of the underseal / seam sealer,

I have a set of Facom scrapers (about £25 for the 3) and they are great for this job, with the shell on its side you can easily scrape off the underseal etc.,

so you could argue if I’m scraping it clean why blast it, well in my opinion you will never get it as clean and rust free as media blasting or dipping,
I blasted my traveller shell, and it’s clean to work with and welds beautifully and you can see exactly what you have left.

Steve

[dp]

I've seen somewhere where they dump a load of dry ice on the floor to make the underside underseal cold & brittle so it chips off much more easily