How about dipping vs media blasting ?

andrewh · Post by **andrewh** » Mon Sep 07, 2015 5:31 pm

I have a rust/rot free California OTS here and have just commenced a full restoration. It occurs to me that whilst the sills are not rotten and just have some surface rust inside having inspected with my borescope , a standard blasting g will not clean this off. Has anyone any "good" experience of acid dipping ?

I have heard horror stories about leaking and seeping acid for years to come, but others swear by it. Surely for an E with good sills its a no brainer?

Oh, and what about the leading? Is that affected?

christopher storey · Post by **christopher storey** » Mon Sep 07, 2015 5:39 pm

It depends what acid is used. The strong acids used for some forms of commercial paint stripping are no good for car restoration work because, as you have stated, there is a tendency for un-neutralised acid to get trapped in seams and to leach out over some years, with catastrophic consequences for a new paint job. However, if you sprayed your shell with phosphoric acid at about a 10% solution, it would kill any surface rust and leave a surface which can safely be painted. Etch primers are usually a mix of phosphoric and a water based primer

andrewh · Post by **andrewh** » Mon Sep 07, 2015 5:45 pm

Thanks Christipher. Interesting , however I am trying to get the inside of the sills, so no way it can be sprayed it would have to be dipped. There is a company SPL I think that advertise especially for Classic Car restorers. I better have a Google and see what the jungle drums sy

vipergts · Post by **vipergts** » Mon Sep 07, 2015 5:47 pm

ANDREW......DONT DO IT

Talk to me...especially no point in doing it if the car is good.

Talk to JD's too they'll tell you the horrors

Plus there is a thread on it here

JagWaugh · Post by **JagWaugh** » Mon Sep 07, 2015 5:50 pm

Andrew,

I had my 3.8 S dipped: glycol process to remove paint, phosphoric acid to remove rust, then multiple rinses, then an epoxy wash primer. The car sat for nearly a decade between dipping and getting the sheet metal repaired, so the wash primer was well worth the money (ca. 1K$). My car didn't have really major rust issues, but it did need parts of the wheel wells, both outer sills and the front jacking points replaced. The Phosphoric dip removed any minor rust, major was cut out anyway. To be really OCD, you would have the shell dipped and phosphated AFTER the sheet metal has been replaced (i.e. dip the whole damned thing twice), but this would be cost prohibitive. 1 year post paint there is no sign whatsoever of anything leaking out or otherwise compromising the paint at the joins. Perhaps the long cure period plays a role (It wasn't deliberate, I just didn't have the money).

As to the lead, some areas (but not all) needed the lead removing and re-loading, I suspect that the lead had not properly tinned to the substrate in these areas.

andrewh · Post by **andrewh** » Mon Sep 07, 2015 6:49 pm

Ok chaps. , thank you all. I had heard Lee that you had a nightmare witht the Charger, I think, but other, my friend Will G has done Minis and loves it. I will check out the thread if I can find it. Thank you as well Jag Waugh. I suspect from the length of time it stood, any contamination was eradicated but perhaps it was just a good job.

vrracing · Post by **vrracing** » Mon Sep 07, 2015 8:10 pm

You might also consider washing the inside of the sills with chelate like Espirit, Evap-O-Rust, Workshop Heroes or whatever brands are available in your area. You build a fluid capture system (kiddie pool or tarp on a framework) and pump it thru the holes on the inside bottom of the inner sills and the ports in the A and B pillars using a fountain pump ($12US at Harbor Freight). The chelates are pH neutral, non-poisonous and don't remove any of the metal. Then you can follow up with a Wurthing, POR-15, Eastwood Internal Frame Coating, epoxy primer or whatever solution fits your religious proclivities. Example of someone doing this on a Mustang.

http://1970boss302.blogspot.com/search?q=chelation

Good luck!

64etype · Post by **64etype** » Tue Sep 08, 2015 12:53 am

I used Evaporust on the entire tub section...inside and out. Drilled a 1" hole in sill rear end cap to insert various wands. Initially dry brushed and vacuumed as best I could via that access hole. Lots of dirt in there. Then flushed with mixture of purple cleaner and hi pressure water. Rinsed with fresh water, force air dried...then Evaporust via a "porcupine" wand (radial spray the full length of sill. Used a 1/4 hp sump pump and the previously explained catch basin. Catch basin drains into catch pan where sump pump resides. Continuous recirculation. Hot pad under catch pan and warm garage is best. Worked great. When the rust is gone, flush again and force dry again. Then Boeshield T-9 followed by Wurth wax or equivalent. No paint or POR15, as it's doubtful it will get full coverage or penetrate in seams and corners like T-9.

I have lots of photos if you take this route for the rust.

"Good enough" would probably be a good dry cleaning and vacuum followed by a thorough pressure flush. Force dry, then skip the chelation step and go directly to Boeshield T-9 and Wurthwax.

christopher storey · Post by **christopher storey** » Tue Sep 08, 2015 9:52 am

Dipping is not necessary to flood the sills with e.g. phosphoric. There is a series of holes along the base of each of the inner sills, and a half inch hole drilled in the rear of each sill will give ample additional access for a spray pipe. Similarly, the internal cavities of the bulkhead ( just as important as the sills ) can be reached from various holes , mostly on the rear face of the firewall

64etype · Post by **64etype** » Tue Sep 08, 2015 2:26 pm

True for a single application of a liquid like phosphoric acid. But even then I doubt every nook and cranny could be accessed given the bracing structure inside the sills. In any case, for a chelation product to work the surface must be wetted continuously for extended periods (many hours...possibly days if the temperature is cool). So for chelation, either dipping, or creative nozzle wand combinations for extended, continuous spraying are required. The side holes along the floor won't work if full and continuous coverage in the sills is expected from a spray. With one exception, the voids behind the seats have access holes and a radial spray wand gets good continuous coverage. The support "box"/frame structure for the IRS can be accessed from a hole drilled in the vertical wall of the boot. The voids behind the fire wall and ahead of the doors also got the chelation treatment. Every derusted area got the Boeshield/Wurthwax treatment.

Another approach for chelation treatment of sills/voids, perhaps even better than spray, might be to block all the openings to a given cavity and top off the void with the liquid....would require some additional strategically placed small fill holes at the top. I'd guestimate ten gallons would fill a sill. Keep the void topped off with a small pump in a catch basin to keep the void filled as there would be leakage. A five gallon bucket of Evaporust is $80 in the U.S. It does "wear out". I used about 15 gallons for everything.

Depends if the objective is to apply a preservative like Boeshield/Wurthwax onto a rust free surface...or to spray something over the top of dirt, crud and rust.

christopher storey · Post by **christopher storey** » Tue Sep 08, 2015 4:45 pm

Well, perhaps Simon as the Chemist here can tell us, but I did not think that H3PO4.H20 was a chelating agent, but merely converted Fe2O3 into Fe PO4 by single bonds in the reaction 2 H3PO4 + Fe2O3 → 2 FePO4 + 3 H2O. Certainly, in my use of it for the last 25 years or so I have never found a need for continuous immersion - a single application by brush usually has been sufficient to deal with surface rust or to prime bare metal surfaces . Incidentally, although I have seen plenty of voids with rust in them,usually the result of condensation , I cannot think of many voids on the E shell where I have ever seen dirt and crud contained within the void, although in contrast that does happen on mark 2 saloons

JagWaugh · Post by **JagWaugh** » Tue Sep 08, 2015 6:30 pm

I wonder if you could add a foaming agent like soap to the evaporust, and use an aquarium bubbler to foam it out. Then you wouldn't need to get the sills fully water tight.

Can't get evaporust here, so no way to try it out.

Andrew

64etype · Post by **64etype** » Tue Sep 08, 2015 7:17 pm

christopher storey wrote:Well, perhaps Simon as the Chemist here can tell us, but I did not think that H3PO4.H20 was a chelating agent, but merely converted Fe2O3 into Fe PO4 by single bonds in the reaction 2 H3PO4 + Fe2O3 → 2 FePO4 + 3 H2O. Certainly, in my use of it for the last 25 years or so I have never found a need for continuous immersion - a single application by brush usually has been sufficient to deal with surface rust or to prime bare metal surfaces . Incidentally, although I have seen plenty of voids with rust in them,usually the result of condensation , I cannot think of many voids on the E shell where I have ever seen dirt and crud contained within the void, although in contrast that does happen on mark 2 saloons

No, phosphoric acid is not a chelating agent. I didn't say it was. Don't believe it's a good stand alone solution for sills or other voids, however.

PeterCrespin · Post by **PeterCrespin** » Tue Sep 08, 2015 8:49 pm

JagWaugh wrote:I wonder if you could add a foaming agent like soap to the evaporust, and use an aquarium bubbler to foam it out. Then you wouldn't need to get the sills fully water tight.

Can't get evaporust here, so no way to try it out.

Andrew

A lot of detergents contain chelating agents IIRC

vrracing · Post by **vrracing** » Wed Sep 09, 2015 1:06 am

JagWaugh, if you're in Australia...

http://www.evapo-rust.com.au/FAQ.html

or NZ

http://www.evapo-rust.co.nz/

or SA

http://www.evapo-rust.co.za/

Chelation for rust and scale removal is standard practice throughout the world and is used to descale and derust boilers and other industrial plumbing. The most common chelate EDTA is in everything including food and makeup as the chelate impedes oxidation and the discoloring that causes.

https://en.wikipedia.org/wiki/Ethylened ... cetic_acid

JagWaugh · Post by **JagWaugh** » Wed Sep 09, 2015 5:24 am

I have in the past used Molasses with good success. For small parts I usually use Hammerite Anti rust (Citric Acid) then a wash with Phosphoric. I may try chelation again on a future project, dipping is expensive here (5000+ $).

Andrew

SEJohnson95 · Post by **SEJohnson95** » Wed Sep 09, 2015 8:23 am

Christopher is indeed right with his equation for the conversion of rust. Chelates are extremely useful things in sythesis and also analysis (using chelating agents such as EDTA to preferentially complex with the metal analyte in order to reduce ionisation interference in Atomic Absorption Spectroscopy springs to mind instantly), so it wouldn't surprise me to hear of their widespread uses. Phosphoric acid is not a chelating agent, the .H20 indicates it is hydrated however?

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