Dipping vs. Blasting

[mpotvin]

I have my 1968 SWT disassembled down to a shell and am weighing the pros and cons of having it stripped by hot tank/dipping vs. sandblasting. Anyone have any first hand experience with dipping? I would prefer to not have to deal with the residual, sand mess. There is some rust and I want to make sure that I get every bit of it. Thanks, Mark

[john1180]

I'd talk to Chris Nielsen, Mark. He just had his dip stripped in Portland recently. Sounds like some real advantages to dipping.

[chris_seven]

All of the dipping processes in the UK use a Controlled Pyrolysis Oven as the first stage of the process.

We have the bodies heated to just below 400 degC in a controlled oven so that the paint and sealant never burns. Bodies are then jet washed and dipped in a Phosporic/Citric Acid solution before being washed and then inhibited.

Works really well and much less damaging than media blasting with all of the potential residual stress issues.

[Haasman]

Wow ... wonderful results. Sure beats a wire wheel! Does anybody do this in California? Northern California?

Haasman

[mpotvin]

I've been talking to the guys in Oregon as well...seem to really know their stuff. They've done a few Porsches, Jags, etc. I'll check in with Chris as well. Thanks and I'll keep you posted.

[luke-44]

... Anyone have any first hand experience with dipping? ...

The only way to go. I've done 2 cars this way. Excellent results both times. Shots below are my TR3 currently under restoration. It shows everything. And forget the old wives tale about not getting the "acid" out of the crevices. That's generally an argument put forth by guys advocating blasting, not the experience of those that have done it. It goes through a rinse cycle that takes care of this. Check your local supplier for more details.

[mpotvin]

Excellent! Thanks for the input and pics. Looks like the way to go. Cheers, Mark

[preS]

The only way to go. I've done 2 cars this way. Excellent results both times. Shots below are my TR3 currently under restoration. It shows everything. And forget the old wives tale about not getting the "acid" out of the crevices. That's generally an argument put forth by guys advocating blasting, not the experience of those that have done it. It goes through a rinse cycle that takes care of this. Check your local supplier for more details.

It certainly is not an old wives tale. In the past I have seen and been offered a 55 Speedster on the East coast (I believe it was in Dayon) that needed to be repainted because the paint was all meshed up due to the acid. The area where it got all weird was on both sides cowl/ front fender / A post. Also two 911s that were dipped in Belgium had paint problems.

I personally think that dipping can be considered but you have to be sure that the shop knows what it's doing. This sounds very logical but both the Speedster and 911s belonged to guy who were well experienced.

Richard

[chris_seven]

We have a shop in the UK that uses Hydrochloric Acid in the dip stage of the process and we have seen quite bad 'bleed' from seams within a few months.

Sulphuric Acid would be even worse as this would re-concentrate even after washing.

The problem is that the seam will collect acid by capilliary action and rinse water doesn't stand a chance of washing this out.

The only way is to use an acid that has a controlled pH and that loses its activity in a short time.

We worked with one of the Pryolysis Oven specialists and another UK Company that carries out E-Coating to develop the Phosphoric/Citric Acid treatment.

We carried out a few trials using old scrap chassis sections and looking inside seams after treatment and e-coating.

We have used this method for 6 years now and had no issues with rusty seams.

[MTemp]

Agree with Richard ...... but in fact I think the key phrase here is "you have to be sure that the shop knows what it's doing".

If you use media, even quite soft stuff, and the operator is not at his best, or is not experienced then he/she can ripple some of these large panels, so that method is not without its risks. Benefit to my mind is that at least what you see is what you got when you get it back. Getting all the media out is a PITA though. Downside is you can only blast clean where you can get access.

Dipping has all the advantages mentioned esp if coupled with the pyrolysis step Chris mentions, but again I'm sure done properly by an experienced shop I'm sure it's fine too. It does have the downside to my mind that if (and it is only an 'if') it is not done well then it won't be immediately obvious, and your problems will surface much later and be much more expensive and hassle to correct.

You pays your money (often quite a bit) and you take your choice - but I'd be driven by local demonstrable expertise rather than any particular method