Fuel tank repair

[machten]

I have a 68 twin filler tank that has internal rust and has had previous (poor) attempts at repair using (I suspect) a combination of body filler and a very light coating of some internal sealant. The rust was never cleaned out properly in the first place, so the issue is now only compounded. As you'd be aware these tanks are pretty thin on the ground (any one got one they want to part with?) and I'm keen to address this now.

I haven;t had to rescue a tank before. I'm happy to repaint, but would prefer to keep the chrome siding intact. What's the collective view on dealing with this? If I finish with an internal sealant, what's the best one (if at all)?

Kev

[wcorey]

Hey Kev,

Tank sealing is likely the way to go if you want your chrome left intact and it's a pretty controversial subject these days, at least here in the usa where ethanol blended fuel has been taking a toll on plastic and composite tanks. There seems to be no one sealing product that has proven to be fail safe, though I'm not convinced that the failures aren't sometimes due to misapplication rather than the product itself being not up to the task.
The big issue is the coating either de laminating or partiality dissolving, leaving a gooey residue that clogs the fuel system.
You have an advantage with the steel tank as most coating systems were made for that and not necessarily for plastic or composite, though they may claim to be. And if you're not seeing ethanol down there you're probably all set with most any reputable sealer anyway.
The two products that come to mind immediately are Caswells and POR5, Caswells getting the nod by most. It's a phenolic ('phenol novolac') based two part epoxy that's purported to be the only thing that withstands ethanol exposure. I've found another phenolic based product made by PPG/Sigma coatings that's made for use on supertankers and tank farms called Novaguard 890 that is claimed be good for 100 percent ethanol but haven't been able to find a source for it, inquiries to the company have gone unanswered. Would likely need to buy it in 55gal drum quantities anyway...

As far as getting rid of the miscellany stuck inside your tank, I'd soak it with a solvent such as MEK, then put a few handfulls of drywall screws in it and shake it about for a time, repeating as necessary. There are also some good rust removing chemicals available for that end of things. Surface prep is really the key to get any coating/ sealing system to work and also most of the work in that process, don't be tempted to cut corners there...


Bill


Bill

[JimF]

I had a metal 450 tank that leaked in the area where the petcock threads were brazed in.

I tried POR-15 and I SWEAR TO GOD I did everything as per the instructions. Neither did I do it fast, I took my time. If the instructions said 'do blah blah for one hour' I took an hour to do it.

The tank quickly redeveloped the leak.

My Mach 1 tank was like swiss cheese tin the same area. Holt Ducati effected the tank repair and then sent it to a radiator shop to be sealed. As much as I can recall the process is very caustic and has to be done prior to a repaint.

It's been fine ever since.

Jim

[MotoMike]

I don't know how you'd go about getting the old sealant out. I have heard of but never tried and can't endorse, putting a bunch of short roofing nails in the tank. count them so you get the same number back. wrapping the tank with blankets and foam or the like and duct tap it on so that it is well protected. Then go to your local laundromat and use their big dryer to tumble the tank for an hour or so... Hehe. let me know if you try it.

But on my 450 tank which had minor rust on the inside and a lot of rust, dings, different paint on the outside, I chemically removed the exterior paint with a store bought paint remover. Then filled the tank with a solution of muriatic acid I got from a swimming pool supply store. (it was in San Diego) I think I used 50/50 with water but don't remember for sure. over night the inside was shiny metal. Rinsed it very well, dried it and then applied tank sealant. The brand was Kreem. a two part that you mixed up, and poured in the tank and periodically tilted to ensure total coverage. I primed the exterior and 17 years later a friend painted it for me. the interior is still holding up.

[DewCatTea-Bob]

____ I'd be very apprehensive about what items are used to dislodge rust from the inside ! ...
I've always used a pack or two of BBs to work-loose rust from the inside (then rinse-out with a solution of water & alcohol) but, even with such non-sharp particle/items, back even in the '70s, it was still-then possible to poke microscopic-sized holes into/through the poor/rusted-metal.
So it ought be better to just use one of the new products which combine with rust, to make it a more stable substance which can be better dealt with.

____ And also covered before... viewtopic.php?f=3&t=241&p=1522#p1487


Hopeful-Cheers,
-Bob

[machten]

Thanks to all for the info. I did quite a bit of reading on the sealants over the last few months as I have recently called upon some old surfboard fibreglassing expeience to rescue an original 750 Sport fibreglass tank for a friend and was looking into a long term internal solution for that. Over here on the west coast of Aus we are yet have ethanol blends foisted upon us (they are used on the east coast), but it is only a matter of time, I'm sure, so I'll be looking to be "ethanol proof".

I found it hard to get a universal picture of the "best" solution in my reasearch. I've dicovered "failures" noted for every product. Of course, you just don't know what is down to poor preparation (Jim excepted!!). I confess, I'm leaning to the Caswell stuff, I think.

I believe I can get the stuff out that is in there with MEK or dichloromethane (common active ingredient in paint stripper). I'll have a good look at the tank after I've done that and decide the next course of action.

Then go to your local laundromat and use their big dryer to tumble the tank for an hour or so... Hehe. let me know if you try it.

You might get your wish Mike, or close to it. If necessary, I have the beginnings of a plan involving compressed foam rubber, and a threaded bar though the tank mounting holes tack welded onto an electric cement mixer with variable speed control

Kev

[JimF]

I swear to God - this is true...

I know a guy that took the eclectic rotisserie motor and skewer off of his barbeque grill and fixed his tank to it so that the skewer would rotate the tank for hours on end unattended while filled with stuff to scrape and rough up the interior.

I will see if he still has the cell phone camera pictures of his set-up.

[Bevel bob]

All of the fuels availiable in the uk now have ethanol in appart from the top BP grade, and as BP are investing heavily into ethanol production I can't see them keeping it eth free much longer. This is one problem that can only get worse when e5 becomes e10 or e20, look whats happening in the States.

[double diamond]

Haven't tried this rust removal process yet but it looks pretty interesting: http://www.sunnymeadcycles.com/files/El ... emoval.pdf
There's another tale somewhere on the web on how to use this process on tanks by fashioning an electrode out of a coat hanger, fitting it inside the tank and insulating it from the tank in order effect the required circuit. Of course, you'd have to seal up all the rust holes if there are any in the tank in order to keep the solution from leaking out. My experience with muriatic acid is that it's impossible to get out of crimped seams (such as where the outer tank is joined with the tunnel) and continues to rust (muriatic is a strong corrosive), even after neutralizing the acid with bicarbonate of soda. Hence, my interest in the electrolytic method. -Matt

[machten]

Once again, thanks for the feedback, I've also studied the reverse electrolisis which looks worth a trial for some applications,and I'd be happy to test it but not on such a rare tank. Also for my situation where I'd like to protect the chrome siding, I don't think it is my first option.

Kev