Gas Tank Restoration

[Lazeum]

I had many issues with fuel starvation due to debris in my gas tank. It has already been coated with resin in the past so the only option to fix the issue for good was to open up the tank, shot-blast it & weld it back.

 

So here are the steps taken so far. I need advice regarding how to weld it back. If somebody could chime in and let me know the best option, I would really appreciate

 

First, obviously, tank was dropped from the car:

 

 

 

I ground the lips to expose the factory welds:

 

 

...so I can use my angle grinder to cut the welds

 

 

I've used a thick knife with a hammer to open up the tank

 

 

...to end up with tank in 2 pieces

  

 

 

Shot blasting process is a no brainer, except I cannot do it myself. My shot blasting cabin is way to small...

 

Next step will be to weld everything back together.

So far, this is how the lip looks like (minus the chips I've cleaned up), both shells are cut in front of each other.

Sheet metal thickness is 0.040" (1mm).

 

 

Not sure what would be the best way of doing it:

- MIG or TIG weld? 

- how should I setup the lips? Should I do it according to option #1 or option #2 on the following drawing? I'm wondering if I shouldn't mill some material out of one shell (the bottom side is easier since no outlets are on the way) and weld a corner instead of a "flat surface". Obviously, I need something sealed (I'll add resin inside the tank afterwards also). option #2 seems more appropriate.

 

 

Extra question: since tank is wide open, I'm wondering if couldn't also add some metal sheet to create some baffles around fuel pickup. Easiest way would a be a simple flat sheet around pickup. More elegant solution would be 4 V-shape sheets to surround pickup, not sure how to make it happen on the lower shell while the pickup is on the top shell...

 

Thanks!

Edited February 18, 2013 by Lazeum

[Tony D]

When it's opened, add your swirl pot and anti-slosh baffles.

 

A proper weld will NOT require sealant to seal!

 

I believe the original is pinch welded, so trimming for a lap may be easier to "disguise" the fact that you opened the tank.

 

A straight edge weld would be easily accomplished with no filler, but would be visible to even casual observers.

[Lazeum]

The tank seems pinch welded. I did not see any signs of heat anywhere around. From a process stand point, it makes a lot of sense (quick, clean, easy)

 

Sealant? I'll add resin that would seal if required but it is mainly to protect naked steel against rust over time

 

Regarding the way it looks, as long as it looks clean & "professionnal", I'll be ok with it. Anybody who knows how the tank looks like will know it has been modified since it will miss the lip all around anyhow.

I did not think about the lack of filler. TIG might be easier than expected then.

 

Thanks!

[Xnke]

If it was me, I'd add the baffles and swirl pot, and when I put it back together I'd stack the top and bottom halves, clamp the remaining lips together and TIG weld the edges, using MIG wire as filler where needed. Sometimes an autogenous weld isn't the cleanest kind of weld, and a little filler rod helps with that.

[AZGhost623]

I had mine refurbed just a few weeks ago by a company in town for $100. They had it for 2 days. They cracked it open. and then they ribbon welded it back together. Im not sure of that "ribbon weld" process, but its what I was told when I inquired. I was too afraid to crack that thing open myself.

[Lazeum]

I believe I will add some baffles inside but not sure about the swirl pot. I'm afraid to do more harm than good. I might end up with only an extra baffle to keep gas around fuel pick.

Since I'll put also some resin as coating, I need to make sure I won't seal up baffles so I will drill 1 or 2 holes on every baffle to prevent it.

 

Regarding the work done, I've removed the outer rubber coating & inner coating on bottom shell. I've used a heat gun, it was a pain with toxic vapors that made me sick.

I've continued on the top side but I give up in the middle of process. I'll see with shot blasting company first if they can deal with it before.

I've tried with my garage equipment, the coating is too soft & too thick to be removed with my tools.

 

Regarding welding them back together, I'll give it a try as it is now with MIG. It might be qquicker and nice enough. I'll smooth everything up anyway afterwards.

Edited February 26, 2013 by Lazeum

[Lazeum]

I just come back from the shotblasting shop. They told me every residu of coating inside/out must be removed to make the blasting process efficient. They can get rid of them but they might destroy the tank this way.

It is a pain to remove but it has to go. Shop owner adviced me to burn everything off.

I'm thinking about using a butane torch but it might take ages. I've thought about making a fire in the yard and let the gas tank shells burning slowly.

[LanceVance]

I've thought about making a fire in the yard and let the gas tank shells burning slowly.

Sounds like the recipe for metal fatigue. Most metals can't stand up to prolonged high heat, much less direct contact with fire before they change on a molecular level.

[Lazeum]

you might be right, I might have some crystalization occuring with such process since I don't control anything: metal chemistry, heat, air contaminants, etc..

I'm also worried about carbonization with wood burning & vaporizing carbon molecules to steel...

[Tony D]

Read Gerárd Metrál's book, he suggests putting leaf springs and truck axles into fires to soften them, making them suitable for use in Clandestine Weapons Manufacture. If anybody asks the debris looks just like that...instead of unfinished barrels, etc!

 

Fire is not good uncontrolled....

[NewZed]

I just come back from the shotblasting shop. They told me every residu of coating inside/out must be removed to make the blasting process efficient. They can get rid of them but they might destroy the tank this way.

It is a pain to remove but it has to go. Shop owner adviced me to burn everything off.

I'm thinking about using a butane torch but it might take ages. I've thought about making a fire in the yard and let the gas tank shells burning slowly.

CO2/dry ice blasting might work.  It will freeze it and make it glassy and brittle.  Mixed CO2 and blasting media might work even better but I'm not sure people do that, but I'd be surprised if someone out there doesn't.  I'm no expert on cleaning metals, just some experience with coatings and materials.

Edited February 28, 2013 by NewZed

[Lazeum]

Dry ice, I thought about it while I was tearing up the gums out of the tank. Unfortunately, it is not so easy to get on this side of the ocean...

As for mixing up CO2 & blasting, you're asking too much It is not as easy as in the US to find good source to work on cars.

 

Some friends suggested to use paint stripper & gas to remove what remains. I'll give it a try this weekend but I'm not sure about the outcome.

Edited February 28, 2013 by Lazeum

[Tony D]

Dry Ice is EXTENSIVELY used in Europe as an "environmentally clean" alternative!

Any Linde or BOC office should be able to sell the media, or direct you to who has the service available.

 

Check with large electric motor overhaul facilities for people providing field cleaning services. Siemens was the contractor we used in Poland (subbed from services UK)

 

The non conductive nature of dry ice cleaning suits it to electrical windings and other places... Along with all the VOC elimination green party nannystate crap...

 

http://www.pclicc.co.uk/Services/cryogenic-cleaning-dry-ice-blast-cleaning

 

http://www.roteq.com.au/teq_clean.asp

 

http://www.cryonomic.com

Edited February 28, 2013 by Tony D

[Tony D]

I believe a Linde agent should be able to be located in...ahem..."France"!

 

Xenophobically speaking, it's more palatable than calling BRITISH Oxygen Company (BOC)...

[Lazeum]

Checking on the internet, I found a source & it's quite affordable: 55€ shipped for 20 lbs.

Anyway, the tank is almost clean, I won't be removing chunks anymore since the layers remaining are less than 0.040" thick.

[Lazeum]

Since last post, I've made some progress

 

First, I've spent 2 full weekends scrapping old material with heat gun, then wire wheels.

I've purchased a heavy duty mask to avoid swallowing fumes, particles & paint, I should have done it way earlier, it is a very good tool to get, much better than paper mask that are more or less useless.

 

 

I ended up with 2 rusty shells. I took pictures of the bottom side only. Top is more difficult to scrap since shape is more complex + I had to clean every inlet/outlet.

 

 

 

 

Parts were then sanded by an outside company. They come up very clean! 

 

 

 

Next step was to remove some material all around on bottom cover. It created a step to weld more easily both parts.

 

 

...following with welds all around, only by spots to avoid making holes. I've added supports as well to hold the tank for further operations & to hold fuel filter in car (not showed on pictures). Toughest area was below filler inlet since both shells are not flat against each others.

There was also a hole with a cap on the corner of the tank. No idea why, so I've plugged it. If anybody knows what it is, I'll be curious to know.

 

 

Tank was ground to remove any sharp edges or material excess. 

 

We have in France a company called Restom providing special products for classic cars. They have a resin (epoxy?) to protect tank against rust & gas. It is an alternative to POR15.

Here's how the tank looks like inside after treatment (product looks like liquid honey - a pain to properly spread it inside!)

There were many little holes on welds, resin covered them all up. Tank is now fully sealed.

 

I've finally chosen not to add any extra baffles or features to prevent fuel starvation with high G's. Knowing how difficult it was to spread the resin, it was a good decision. I would have had to cover with resin the features BEFORE welding everything together with the risk to cook the resin or to block some paths.

 

 

Last step was to spray some paint outside. I did it with a 2 components epoxy paint that do not require any primer. Properties once cured are advertised as tough as powder coating.

 

here's how the final product looks like now.

Resin needs 2 weeks at least to cure, paint needs 48hrs. 

 

 

Edited April 3, 2013 by Lazeum