T-5 / T-6 Gas tank repair

[Jbrooks]

JTR70

The time in the round tank for the bottom was about 6-8 hours. That half went pretty quickly, since it all fit in the trash can with a little effort to get the can to flex. The cathodes were close to the metal of the tank (anode) so the ion travel distance was only 3-5 inches. The sheet metal cathode was new and clean for the top. The larger tank took over 24 hours. Same power supply and cathode more water larger distances. I scraped the cathodes to clean the plates but not being fresh it took longer due to the resistance of the deposits. This is not a fast process but it is cheap and if you are not in hurry its fine. There is a thin carbon deposit on the metal after the FeO4 is removed, comes off with a wire brush.

The process changes the rust into an ion and moves it to the positive plate. This causes allot of crud deposited on the plates, resistance goes up and it takes longer, For the filler tube I placed a steel wire, down the center with a wood plug to electrically insulate it. rust came off and stuck to the wire. The tank came out better than I expected, I could have sand blasted it faster but this is much easier on the metal and no stretching. Electrolysis finds the pin holes, and it gets in behind spot welds and it theory is as effective as any other chemical process I know of. The best part is it only effects the oxides not the good metal. Low voltages and low current, and unattended.

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Still playing with the pulse TIG on the 22 GA coupons. But its actually pretty easy once its dialed in, and the computer controlled welder, does the work, makes it much better. Set for 28-30 AMPS max power. Then set the pulse for 1.5-2 pulses per second. 25A at 30% high 18-20A 70% low. Machine is set for full pedal is 30a so the arc starts then drops it back, then hits it again at full. It forms a puddle, melts the filler, the cools off a little then hits it again. The filler is laying on the gap so no dabbing the rod, and the puddle is exactly the same size each pulse. Not allot of heat into the metal and not allot of foot movement. You just move the torch along the seam. Takes some practice but, just tic tic tic tic tic . Very small arc, #6 see through glass cup. If it looks like its going to blow a hole you just lift your foot for a second, let the puddle cool some and go back at it.

I can't say enough about how cool the EVERLAST welder is. The variable polarity, center voltage, wave forms, frequencies and arc stability are amazing. The computer geeks in Silicon Valley have learned how to weld. https://www.everlastgenerators.com/

Thanks for looking

[JTR70]

Oh, I misread that, you're TiG'ing not MIG welding. Different animal, sorry about that...

[Jbrooks]

Well guys it’s a BUST.. this tank can’t be saved, maybe with POR15 but not with lead (Pb). I was using 37/63 auto body lead over the Eastwood flux.

The electrolysis was very good at removing the rust, can’t complain about that at all. But the tank is so pitted, I can’t get all the rust from the pits. This is causing the solder not to want to stick.

tinning paste applied, then heated and tinned but the solder puddles and will not flow



The tinning paste works fine on CLEAN metal. I am very impressed on how well this part of the process works, the Tinning Butter flows well on test coupons, and it is pretty easy to lead over. This tinning alone might be enough to prevent future rusting but its is not going into the little pits. I feel they will rust more in the future. But on the tank the a new lead layer will not stick unless you grind it down to bear metal. Then tin it and lead over the tinned section, it will stick and flow out about 1mm thick just fine, but grinding this tank will leave the tank so thin it will probably crack over time.

Here is after grinding smooth then tinned and soldered ( ~1mm of lead)

I tried wire brushing, sand blasting and an even an acid dip. The pits are too deep and I can not get the new lead to stick. The lead will puddle but not flow like it should. My be me and my techniques, but it’s a bust, was lots of fun and I can still do the door gaps and blended patches, but not with rust. The acid did react within the tiny pits, but just not clean enough to allow the flux to finish cleaning and get the solder to fill the depressions.

I did learn that if you need to weld over a previously leaded section. You can heat it and wipe of the lead, and then weld with out too much contamination. Both with MIG and TIG processes.

Thanks for watching, I am back to the DYNO build, and avoiding COVID-19.

[JTR70]

You don't have to call it quits just yet. Take a run down to your local hardware store and buy some muriatic acid. It will clean all of those pits 100%. You've already got the heavy lifting done so the acid will work very quickly. Doesn't have to be tanked at this point either. A few rounds of brush applications will turn the trick. Once its clean you just have to take care that the acid is thoroughly neutralized with soapy water and a final rinse. You'll want to blow it dry with an air hose to reduce the flash rusting. The surface will turn gold-green on you during this process but a quick wire wheeling will take it right off. Then you're ready to lead wipe. Give it a shot....Justin

[Phil Planck]

Or coat both halves with por15 tank sealer leaving a gap where you want to rejoin. Weld/ lead the joint then slosh por15 around just the joint.

[Phil Planck]

I put a bore scope in my 63 tank. Hard to capture pictires but appears mostly just surface rust. I bought the Por 15 kit with cleaner, etcher and sealer. I usrd this on my 912 tank 5 years ago and its holding up well. 912 sender cover plate fits the T6 tank so ready to add cleaner

[tperazzo]

Good effort John! If it's too far gone it's just gone.
Here are a couple thoughts:
It's possible to do electrolysis on tanks without cutting them apart. Well, Ok the baffles adds a layer of complexity.
Fill the tank with washing soda solution and then drop an anode rod in the tank sender hole. Don't let it short out to the tank.
The other side of the baffle might require a hole to be drilled?

Regarding the pits: If there aren't too many a TIG welder can fill them up. TIG has enough cleaning action to get steel to stick. It will likely contaminate a few tungstens, but worth a try.
If there are hundreds of holes, then your time isn't worth chasing all those.

Love your willingness on this! PM sent regarding the anemometer. Sorry for the delay.

[Jbrooks]

Tom, that tank was too gone to repair. I think you could do electrolysis with out taking the tank apart, especially a T2/T5 tank with the big filler.. Getting a large enough anode surface area inside will be a problem. You might have to do it a few times. The top upper surface was the worse part of the tank. I would not even attempted it until I watch you build your 911 tank.

I was using 4, 18 ga strips. (4"x30"), they were gone in 24 hours, the amount of scale was supersizing, The problem was thousands of tiny pits that still retained the oxides, even an acid wash did not clear them enough for the flux / solder to stick, just would not flow out. POR15 might work, or maybe Glyptal but I was looking at welding them back together, I did confirm you can tig over the tinned lead seam with out contaminating or weakening the welds. Using large .035 mig wire, "Lay Wire" in the seam, 4Hz pulse tig 25/15 amps 20-80% high works well on the thin sheet. The wire melts on the high pulse and cools on the low. It is slow but makes a good bead and seal.