T-5 / T-6 Gas tank repair

[Jbrooks]

Been off line for a couple months. Staring to get back in the shop more. Have a couple gas tanks to look at. Had a couple new ones that leaked, and finally went to Stoddard and bit the bullet. Dansk tanks have a poor pinch seam welds and wont hold fuel. Mike DeJonge was pretty good about taking them back, no questions..

So I watched Tom Perazzo's electrolysis rust removal video on YouTube a couple weeks ago and said why not see why the old tanks were leaking. Photos are from a 65 T-6. We changed the tank a couple years ago and its was sitting around taking up space. I decided to split the tank and look inside. Boy was I surprised at the amount of rust inside the tank. The entire upper surface had about 2-3mm of exfoliated scale inside, big crusty layer. Just the vibration of the saw, loosed about a cup of the scale.

[Jbrooks]

[Phil Planck]

John
Are you planing to put this tank back together? I have been delaying sealing my T6 tank for 2 years due to concerns about baffle preventing good coverage.

[Jbrooks]

I used sodium carbonate ( Washing Soda) as the base mixed with water, 18Vdc and 5-6 amps for 18 hours to treat the tank. I used a 30 GAL trash can to start, then moved to a 50 gallon plastic bin. Does a very good job of removing the rust, appears to be as clean as Evaporust but much cheaper on something this big. The washing soda was about $9.00 a pound and it only takes cup to treat 25 gal of water. Its is not a fast process but will remove all the oxides from the steel. The process leaves a very thin layer of carbon on the steel after cleaning. This layer is easily removes with a soft wire wheel The filler neck is too big for the trash can so I made a couple wood plugs and placed a wire inside the tube and did is separately. There are many pits in the inner surface. I was really surprised on how much rust had accumulated on the interior. specifically the top of the tank. shine it mostly sees the ullage above the fuel and drys off after driving it was amazing. tossing something in the trunk and flexing the tank skin could dislodge the crusty bits and block the fuel fine.









The outside of the tanks looked fine but everywhere the tank and started to rust under the paint, it lifted the paint. it flakes off with the wire brush and a black speck appears where the surface was damaged,

The overall plan it to clean the tanks, then using body solder to tin the inside surfaces with lead and welder up. I may run a solder bead around the outside after I finish just to be sure no pin holes or slag inclusions in the weld but that's later.

new tanks are available and easier, but fixing it seems like a new adventure. Still working on the Engine Dynometer, drive shaft splines are outsourced, awaiting them to be made.

[Red911]

Hi John,
Just a question, when you tin the inside of the tank, will weld stick to the outside? I have seen somewhere that you have to remove solder before you weld.
Tom

[JTR70]

Really like this method of rust removal John. How long did each submerged section take to clean? What is most interesting about this process is that there is no residual acid to worry about down the road. Thanks for sharing this. Justin

[Jbrooks]

Phil

My first venture into tanks so bare with me.

I will put this one back together, I cut it just above the pinch weld. I will TIG it back then probably run a solder bead over the weld. The baffle is attached with spot welds along the bottom and almost touches the top. There is a small Gate or Gap in the center bottom of the baffle, probably 5mm tall and 20mm wide for the gas to drain into the lower half. Getting the lower portion clean and the POR into the bottom half will be a challenge. You could put a small chain into the drain fitting sender and shake it around but I don't know how to get the debris out once it is loose. The upper half is not hard with the filler tube and sender access,

I am going to tin these with solder and then weld it back together. I thought about painting this with POR prior to putting it back together, but the heat from welding and solder will damage the coating. After seeing the inside and the clearances, I would suppose that a sealed tank with out splitting it or at least opening a big access hole in the top is only 50-60% coated. The top surface had the most rust. you can see in the lower before photo the amount of loose material that fell just from the air saw cut.

Red911

good question, I have no idea, seems the lead would contaminate the weld, but low heat and small beads might work. If I can get it tacked in place, I can always solder the cut closed. We will see.... Its an experiment .... at least the rust is gone

[Phil Planck]

I got myself a bore scope for Christmas. Will try it out on tank innards.

[roy mawbey]

That was very interesting to read. pleased mine is rust free thank goodness.

Be interested to see the finish resu=lt

Roy

[Phil Planck]

John
Can you determine how the flange is sealed? Any solder in it?

Roy
The T6 tanks seem to be much more prone to rust than the earlier tanks.

[Scott B]

Great read. I got a new tank a few years ago from restoration design I plan on using. Did you pressure test the tank to determine that it leaked?

[Jbrooks]

Scott... Make a leak tester from a 2.50 X 18 bike inter-tube. Cut it off with about 10-12" either side of valve stem. Fold over and glue one end to seal it then make a wood plug that is a slip fit into the filler neck. Then plug the holes in the tank city covers and corks. Put the wood plug into the inter tube push it into the neck and inflate the Inter-tube. If it passes the thin part of the neck it will inflate and seal. Just blow up the bike tube, then spray with soapy water with a squirt bottle. It will probably leak at the pinch weld. If so it may be possible to use short tong spot welder and seal it up.

Phil... Originally it's rolled seam weld on the flange. Two wheels pinch and weld as it rolls along the seam. No solder or sealer. It's like a continuous spot weld. I can't replicate this, or at least I don't think, I can. So I will TIG it and solder over the weld.

Welding machine video https://youtu.be/bg_fDRr7tUc

[Phil Planck]

That seam welder us a serious looking piece of equipment.
Thanks John.
Guess I wont be trying to pry that seam open like a hem flange.

[Jbrooks]

All .....

Did some experiments today with the welding and solder. I will edit this and add some photos later if my iPad will corporate. I made some coupons to simulate the tank walls today. Tinned, welded, played mostly. The tank half’s are clean and ready, still debating the POR-15 or lead coat inside.


I tinned the coupons with "tinning butter" a flux and powdered solder mix Eastwood sells. Its old copper/tin roof seam sealer paste. Then after they were tinned we tack and butt welded them together to check for contamination, inclusions and strength. That went well overall, the tacks and 30mm seam weld worked. I was using .032 E70 mig wire, I think was too large for the 22 gauge stock, welds were OK but had a tall bead. I have some .023 E-70 but too lazy to change the spool. I also have some .023 E308 and will try that also tomorrow. I put the coupon in a vise folded the coupon away 90 degrees then back straight up then back toward me 90 degrees and back up and over again. The coupon tore but not the weld.


then I took solder and went over the joint. Uses a torch first and a big 400W soldering iron to fill the gap and cover the weld. I used three types of solder rosin core 60/40, lead free tin and 37/64 body solder. All three worked OK and flowed and filled as expected. Using a big soldering iron is probably how I will deal the tank. Much easier than a torch and less paddling and pushing the solder around. It also works a much smaller puddle and you can hold the bar to the top of the iron and it flows around the point and you just push the iron. I also found that using the iron to melt the "tinning butter" it will tin inside the seam and out the other side. Then will apply the solder, it wicks through to the far side, sealing the gap.

out of photo space See above.

[JTR70]

Interesting experiments John. Definitely, 22 gauge is really thin and tricky to MIG weld. A balancing act to apply it hot enough for decent penetration without blowing through as you go. O32 does seem a little heavy for your coupons. I bought a spool of 023 some years back for use with pitted thin OG metal but I pulled it out shortly afterwards as it was just too thin for my liking. If I turned the amperage up for good penetration the wire itself wanted to melt back towards the tip which constantly interrupted the bead pass. As I turned the amperage down to limit this the weld bead was too cold and more or less just sat on top of the joint. I've found that 030 is really the best bet for welding thin as well as old pitted metal. Aren't you dealing with a lot of weld splatter with the tinning in your way?

[Jbrooks]

READ THE Below first, I ran out of room for the photos....

After folding the coupon until it cracked at the end of the weld, I ground it down looking for inclusions and contamination. Then I beat it back flat and soldered over the weld to see how it would fill, then folded it at 90 degrees again. All went fine. Soldering over the seam was really easy with the Iron, eliminates the flame heat and paddle which I am not good at anymore. I found they wetting the flux with the iron, caused the flux to flow to the far side through the butt seam and the solder will flow and fill the gap. All the different solders works about the same. Auto body bar was the easiest, then the lead free tin roll and finally the rosin core. the rosin is hard to remove



So I will repeat this again with the smaller and stainless wires and also TIG the weld and re solder them I want this to be strong and sealed. I am also going to try "lay Wire TIG" on the seam to butt weld it back together,

So far, the Tinning the inside of the tank will work easily using the "Tinning Butter" . The tinned sections so far have not had enough tin or lead to contaminate the weld or reduce the strength. The welded areas take the solder well and can be smooth and ready to prime. Life is good

[roy mawbey]

John very interesting to see the results and what a good idea to trial the methods out first!!

Well done.

Roy

[Red911]

Hi John,

You have done some excellent research for the other posters on Justin's site. Thanks for experimenting and sharing.

Tom

[Jbrooks]

Tom Thanks.

It looks like the lead in tinned area is thin enough to vaporize when the puddle forms. I have see the leaded fillers contamination in the weld. But from what I have seen on these coupons it does not appear to effect it.

I got a new welder a couple years ago, still learning with it. (its in the tools section) I spoke of maybe Lay Wire Pulse TIG for the tank. Below is a video if the technique. Its is also pretty good for brazing but you need a special bronze rod, but this auto pulse mode is pretty amazing for sheet metal and patch panels butt welds, after you get it tuned in its amazing. you can put in a bead that just need a little hammer and dolly work over the bead and sanding. Super for inverted welding, like under a floor pan, not as many splatter drips on your chest.

This is a little thicker material than a fender patch but the technique is the same. This method is slower that MIG on the welding, but not as much post clean up and finishing.

https://www.youtube.com/watch?v=P72VXYmZr5Y

thanks for looking