[slightly.dusty]

I recently picked up a CX500 standard tank on eBay that I paid way too much for and looked to be in great condition. Low and behold during my initial rinse out I discovered it’s more of a colander than a tank.

I lurked this forum plenty to seek others who have ran in to this in the past, and figured I should log my efforts to refurbish this tank in the hopes of helping someone else along the way.

The tank in question:

The colander:

My basic plan is:

Chem etch interior (acid wash)
Electrolysis interior
Rinse and dry
Dig & TIG the pitting
Seal tank with POR15
Fare out weld mounds and begin the normal process of exterior refinishing.

I expect this to go exactly as planned, of course.

 

[slightly.dusty]

Chem etch:

Using distilled vinegar and rotating tank periodically to acid wash the walls as evenly as I can.

Rust before, and after the front portion sat for about 8 hours:

2 days, a multitude of reorientations (each with a sturdy 5min long shake), and a good rinse after:

 

[slightly.dusty]

Sanding and acetone to reveal and scarp out the pitted areas.

Yes those are all holes, and yes this tank is in some big trouble. Please note that the title of this thread is an attempt.

If we can bring this tank back to life safely it should provide hope for other old corroded tanks, if not, we’ve learned a valuable lesson about the extent to which one can bring a gas tank back from the dead.

 

[slightly.dusty]

All fixed!

Just kidding but it should hold the electrolyte in at least enough to get the job done.

I want to try to run an electrolysis campaign before I weld on the tank to get as much rust out of the substrate as I can. I don’t want to pull too many oxides in to the welds, increasing the porosity and creating a “foamy” joint.


Poor man’s electrolysis setup:

Battery charger and the bikes battery used as the power source.
Electrolyte consists of 1tbsp home made washing soda (baking soda baked at 400f for 30 min) per 1gal water.
Anode made from a mild steel tig rod.

Box fan blowing out the garage door because remember, we’re manufacturing hydrogen.

Will bubble away and top off electrolyte for a day or so until it looks cleaner in there.

 

[D-Fresh]

Are you going to try and weld each individual hole or cut out the bottom area where the holey part is and weld in a patch?

 

[D-Fresh]

You are correct though. From the pics the tank looked nice from the top side, bummer.

 

[danroy323]

Here's how I repaired a similar looking situation on a tank.

My 1977 Honda Z50 minitrail was starting to leak gas through the bottom panel. Once I had cleaned the inside with phosphoric acid I had a multitude of holes just like on your tank. All were on the underside (not visible) part of the tank. I suspect that honda used thicker steel on the visible part of the tank, probably for dent resistance. I wanted to keep the original paint and stickers on the visible part of the tank so I taped all the visible part with 2 layers of duct tape and sandblasted all the underside. This opened yet more holes through the paper thin sheetmetal. I then mixed a large batch of JB weld epoxy and coated all the affected area (pretty much all of the lower part of the underside) with a nice coat, about 1/16in thick. Once cured I painted the underside of the tank with Chevy orange engine paint which surprisingly matched the top side really well.

I did this back in 2006 and to this day it hasn't leaked yet. I could also have lined the interior for an even better job but was not aware that such liner kits existed back then.

Just my 2 cents.
Dan

 

[slightly.dusty]

Here's how I repaired a similar looking situation on a tank.

My 1977 Honda Z50 minitrail was starting to leak gas through the bottom panel. Once I had cleaned the inside with phosphoric acid I had a multitude of holes just like on your tank. All were on the underside (not visible) part of the tank. I suspect that honda used thicker steel on the visible part of the tank, probably for dent resistance. I wanted to keep the original paint and stickers on the visible part of the tank so I taped all the visible part with 2 layers of duct tape and sandblasted all the underside. This opened yet more holes through the paper thin sheetmetal. I then mixed a large batch of JB weld epoxy and coated all the affected area (pretty much all of the lower part of the underside) with a nice coat, about 1/16in thick. Once cured I painted the underside of the tank with Chevy orange engine paint which surprisingly matched the top side really well.

I did this back in 2006 and to this day it hasn't leaked yet. I could also have lined the interior for an even better job but was not aware that such liner kits existed back then.

Just my 2 cents.
Dan

I had considered the epoxy or JB weld approach, but I need the weld practice anyways and might as well fill the holes with as similar material as possible.

This is the immediate result. I should have given it a little longer in the electrobath, as oxides were definitely coming through the weld as expected, but that’s another added benefit of the weld, I was able to reflow it a few times to bubble the impurities to the top (see the volcano effects on some of the spots). I also went a little high on current to blow out any week spots and hopefully overfill areas that were close to punching through.

I took my time as to not heat the work up too much and was able to avoid cooking the paint or vinyl on the outside of the tank. It looks better now that I’ve ground it down (grinder and paint makes me the welder I ain’t), I’ll get a picture up later.


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