acid stripping paintwork

guyjohnwood@aol.com · Post by **guyjohnwood@aol.com** » Fri Jan 31, 2014 6:11 pm

Dear all,

My IT skills are rubbish, so you may have received this already.

The series one FHC I am restoring will be ready for having the paint removed in about 2 weeks. Much debate in the workshop and pub about acid stripping vas sand blasting. My lead restorer is worried that the acid route would result in some residue, which would bubble in the joints in years to come. The other restorer reckons this is not so, and it is the best way to go. So, can anyone help me please, and maybe recommend someone to use.

Also, I am going dark blue, and have just read a post about dark blue being almost black - ugh ! surely not. Still deciding on trim colour, maybe light blue.

Thanks in advance

Guy

Post by **Heuer** » Fri Jan 31, 2014 6:28 pm

Lots of views on this:
http://etypeuk.com/forum/viewtopic.php? ... +stripping
http://etypeuk.com/forum/viewtopic.php? ... +stripping
http://etypeuk.com/forum/viewtopic.php? ... +stripping

SteveG · Post by **SteveG** » Fri Jan 31, 2014 7:24 pm

Guy,

I went through the same 'hand wringing' process deciding to go with dipping or blasting. In the end, after listening to all the advice on this forum I went with media blasting. I asked the guy responsible for doing the work to make sure he kept the pressure down when blasting large expanses of sheet metal, (i.e. the roof & bonnet sections) to avoid too much heat build up and distortion and am very pleased with the result. The tub was then put on a rotisserie and whilst doing the metal work it was turned over and over. After much use of a hoover the vast majority of the remaining media, which I think was ground walnut shells, was removed. Needless to say I am pleased with the result and can be confident there is no residue from any dipping process remaining that may later manifest itself in any paintwork.

My own opinion was that once the job had been done and the car was back to bare metal there was little to come back and haunt me at a later date.

vipergts · Post by **vipergts** » Fri Jan 31, 2014 8:42 pm

Been there...done that and

NO

Don't do it

Dark blue as in Jaguar Dark blue is not black...Here's mine

guyjohnwood@aol.com · Post by **guyjohnwood@aol.com** » Sat Feb 08, 2014 3:09 pm

many thanks to those who answered, really helpful

64etype · Post by **64etype** » Sat Feb 08, 2014 3:20 pm

guyjohnwood@aol.com wrote:Dear all,

My IT skills are rubbish, so you may have received this already.

The series one FHC I am restoring will be ready for having the paint removed in about 2 weeks. Much debate in the workshop and pub about acid stripping vas sand blasting. My lead restorer is worried that the acid route would result in some residue, which would bubble in the joints in years to come. The other restorer reckons this is not so, and it is the best way to go. So, can anyone help me please, and maybe recommend someone to use.

Also, I am going dark blue, and have just read a post about dark blue being almost black - ugh ! surely not. Still deciding on trim colour, maybe light blue.

Thanks in advance

Guy

There are chemical strip shops in the U.S. that remove the paint in one chemical vat, and then submerge the part in a second vat of Evaporust type chemical to eliminate the rust. The second vat also neutralizes any chemical residue from the first. The beauty of the process is that even the voids are cleaned up. Not sure if such facilities are available in your location.

christopher storey · Post by **christopher storey** » Sat Feb 08, 2014 6:06 pm

The facilities Eric speaks of are ( or perhaps more accurately were, because I think a number of operators have closed down ) available nearly everywhere. They are a disaster. Ask CMC for their views on the subject, but hold the phone a long long way from your ear !!

Arbington · Post by **Arbington** » Sat Feb 08, 2014 6:37 pm

I had a car 'dipped' in 2008. In 2010 I had the doors re skinned and the front chassis rails replaced...

The back end was always good.

They didn't clear out the residue well enough. the car was lifted from the vat back end first so it all tipped to the front.
Never again.

64etype · Post by **64etype** » Sat Feb 08, 2014 7:38 pm

christopher storey wrote:The facilities Eric speaks of are ( or perhaps more accurately were, because I think a number of operators have closed down ) available nearly everywhere. They are a disaster. Ask CMC for their views on the subject, but hold the phone a long long way from your ear !!

The shop in the DFW area is going great guns and takes in very high dollar chassis from all over the country. If you're thinking of the old Reddistrip process I'd agree with you, as I had a car stripped by them years ago and had issues with acid residue in the voids. The newer process uses highly allkeline chemicals for the first stripping process, and as I said, the evaporust type chemical takes off the rust and neutralizes anything left from the first caustic (not acid) process. I had my doors and the hatch done by them and couldn't be happier. I washed off the waxy (protective) residue with some purple stuff cleaner, rinsed, etched, and then went straight to epoxy primer. Zero issues, and that was three years ago. I suspect CMC has zero experience with the newer process and is thinking about the old Reddistrip acid dip. Have you actually visited a facility with the newer process or seen/dealt with parts that they deliver??? You would be amazed. Apples and oranges.

Moeregaard · Post by **Moeregaard** » Sun Feb 09, 2014 1:30 pm

When I stripped my '65 FHC for paint, back in 1992, I sent the doors, tailgate and bonnet out for dipping. L&M Stripping in Los Angeles did the work and could not have been happier. I believe they use a caustic-soda solution, along with some manual labor to remove the stubborn stuff. Everything came back very clean and I was able to prime everything that same day. I did find out that the door drains are secured with aluminum rivets, so those are still lying in the bottom of L&M's tank to this day. All internal areas were primed with zinc-chromate primer and Waxoyled after the final finish was applied, and I had no problems with anything creeping out an ruining the paintwork later.

I did have an Austin-Healey Sprite dipped by Reddi-Strip, back in 1982 (this was before California chased them out of the state), and their process did leave a lot of residue in the corners.

Classic Jaguar in Texas use media blasting, but they also open up the bodywork during the refurbishment process, so getting stray media out of the bodyshell isn't an issue.

christopher storey · Post by **christopher storey** » Mon Feb 10, 2014 11:55 am

Since I would regard CMC as probably the premier Jaguar restorer in the world, I think I'll rely on their advice

rfs1957 · Post by **rfs1957** » Mon Feb 10, 2014 12:16 pm

Is 3 years ago long enough to judge whether there's something nasty brewing in the seams ?

"The newer process uses highly allkeline chemicals for the first stripping process, and as I said, the evaporust type chemical takes off the rust and neutralizes anything left from the first caustic (not acid) process."

"Neutralizing anything left" when it's been full of alkalines means using acids, presumably ?

Please fill us in on the exact chemistry. I'm fascinated by rust that Evaporates.

I cannot see the point of filling inaccessible box-sections and every nook-and-crannie of a laminated baked-bean-can structure with a potentially corrosive penetrating fluid that is likely to leave an inevitably hygroscopic residue in precisely the areas I cannot see or clean, removing in the process (from within the box-sections) any factory-applied protection (paint) that I will never be able to replace.

Whilst we're looking to move away from elbow-grease and pain, and find this sort of quick-fix, why hasn't someone developed iPhone App that will do it for us, and send an SMS when it's finished ?

PeterCrespin · Post by **PeterCrespin** » Mon Feb 10, 2014 1:08 pm

No idea of the merits of these processes, and I have no dog in this fight, but there are plenty of aqueous baths that could dissolve away caustic soda used to strip organic materials such as paint from ferrous metal components. Same goes for flushing components and of course acidity is not bad per se as it is precisely what is used to etch prime body shells.

I too am nervous, however, about capillary action harbouring traces of unhelpful chemicals. but then to the extent that such fissures exist all over an old-school mass-produced body shell like the E, the same capillary action would draw in any neutralising or subsequent washing solutions and etching soltuions as well. The depth of penetration is limited largely by viscosity and I could easily imagine that neutralising/flushing baths could be lower viscosity than the caustic stripping liquor and thereby ensure no residue.

Meanwhile, heat at various stages would drive wetness out, so I don't think it's a no-brainer that all bath stripping/priming technologies are dud. Modern cars with a decade of rust guarantee use essentially similar technology and electrophoresis even 'powers' beneficial creep into all the inaccessible seams.

I would tend to favour dry methods though, unless you count ice blasting as wet?

Pete

vrracing · Post by **vrracing** » Mon Feb 10, 2014 1:18 pm

Rory,

Alkaline is the opposite of acidic on the pH scale. Soap is alkaline while vinegar is acid. Wikipedia has good articles on acidity...

https://en.wikipedia.org/wiki/Acid

and alkalinity...

https://en.wikipedia.org/wiki/Base_(chemistry)

Alkalines are often referred to as "base". Essentially, acids have a Ph below 7, neutral (water) is 7 and alkalines (bases) measure more than 7.

Paint stripper is alkaline. Metal Prep is acid.

The "Evaporust" is a brand name for a chelation agent.

https://en.wikipedia.org/wiki/Chelation

It doesnt actually evaoporate rust, that's just marketing. Chelation is a chemical reaction between a chelation agent and metal ions. The chelation molecules bind with the rust and pull it into suspension leaving the good metal behind.

When someone gets heavy metal poisoning they use a chelation agent to remove the metal from their blood.

The advantage of chelation for rust removal is that it is pretty much pH neutral and chemically bonds only with the rust and won't touch the actual metal. Acids, bases and mechanical rust removal always remove good metal with the bad.

A common "poor man's" chelation agent is molasses. You can search youtube for "rust removal" and you'll find a lot of examples. Here is a good article on using commercial chelation products on large body panels.

http://1970boss302.blogspot.com/2011/06 ... nk-im.html

Good luck with your project.

Jim

rfs1957 · Post by **rfs1957** » Mon Feb 10, 2014 2:08 pm

Sorry, the alkaline-acid query was meant to be "irony".

64etype · Post by **64etype** » Mon Feb 10, 2014 4:12 pm

rfs1957 wrote:Sorry, the alkaline-acid query was meant to be "irony".

A pint of Evaporust is inexpensive. Buy some and try it out. It works quite well, especially when heated...which is exactly what's done in the commercial process I contracted for the doors and hatch. I elected to derust the tub and disassembled bonnet in my garage by building a catch basin under the rotisserie, placing a sump pump on a heated pad at the low point, and then circulating the warm fluid over the body one section at a time. A set of spray wands took care of the inside of the sills and voids, which I also warmed with a heat gun.. The tub was oriented to different angles on the rotisserie to ensure the fluid flowed back over every surface. A before and after scope check showed the interior surfaces to be rust free....spotless. When the Evaporust process was finished, I flushed everything with diluted purple cleaner, and then dried with hot forced air. Then Boeshield T9 was pumped into voids until it dripped out of the seams and around the rivets. Boeshield is a machine tool preservative with excellent penetrating characteristics. It leaves a very thin waxy surface when dry. The final step for the voids was Wurth wax. Without opening the sills and voids, this is the only way to clean them up and preserve for the long term. This was a very time consuming process, but there's no better way to do it correctly. Most people wouldn't take the time. But don't knock it 'til you've tried it. Same for CMC, whoever they are.

vipergts · Post by **vipergts** » Mon Feb 10, 2014 9:07 pm

My car started bubbling and it hadn't turned a wheel in 3 yrs...obviously hadn't got wet either

vrracing · Post by **vrracing** » Tue Feb 11, 2014 3:04 am

Pictures or it didnt happen, Eric!

Dave K · Post by **Dave K** » Tue Feb 11, 2014 4:46 pm

Car factories do it by first washing the body in white with detergent, then acid wash, rinse, alkali wash, rinse, phosphate, rinse and then electrophoretic dip and rinse.
That's the way they did at Mayflower where they made the DB7 and dipped other Am's, London taxis, DAF cabs and NATO trucks etc,.
It is the industry standard and gives the 10 year corrosion guarantee.

Dave

Post by **Heuer** » Tue Feb 11, 2014 4:49 pm

Yes but they a) don't have any rust or pin-holes and b) don't have any old paint or road muck that could trap the chemicals.

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