I've just found out that the tank liner coating (aftermarket, and probably Kreem brand) is coming completely off of the inside of the tank - not only in flakes, but in kind of thick, blistering sheets. From what I can feel with my finger, it's like thin flexible plastic in there.

Radiator shop wouldn't touch it, because they know their acid (probably muriatic acid) won't dissolve the stuff.

Who knows what will dissolve cured Kreem so that I can start fresh? I've read that acetone will do it, but I'd like to know for sure before I start filling the tank with caustic (and messy) chemicals.

 

Acetone for about 48 hours, Seal it up good so you can rotate sides / top / etc. every so many hours. Wouldn't hurt to put some nuts or ball bearings in it so you can shake it every so often. Repeat if needed.

They either didn't remove the old liner or etch it proper before they kreemed it.

 

+1 on the prep work.... It's very important that the inside is very clean and dry before lining the tank with whatever brand you use.

 

what is this stuff and why would you line the tank?

 

Without tank liner coating, there is bare metal inside. Rust would be a problem in no time. H-D tanks all come lined with whatever they use. Aftermarket tanks are bare metal when they're new/sold and all manufacturers advise using something like Kreem. I know there are other brands out there, and depending on whom you ask, you'll get differing opinions on their quality.

My particular problem is that the Kreem (I think it's Kreem) is dried out and pulling away from the inside metal of the tank as if it were a bladder, but much more stiff. I can stick my finger in the fuel filler hole and feel a huge plastic bubble that has come loose from that side. Which would explain why I only get 100 or so miles out of my 4 gallon tank . Where the stuff was thinner, it's flaking and sounds like I have a pound of metal shavings inside the tank now when I turn it end over end.

Once I get the sh!te out of the tank, I'll only use something like Ospho to treat the bare metal so that it won't rust. Leaks won't be a problem with this tank so I won't coat the inside with anything.

 

Once you get the old liner dissolved, treat the inside with hydrochloric acid while you apply mechanical agitation using small metal or stone pieces to abrade and bust rust loose....Then fully neutralize the acid....From there apply the complete Kreem process starting with their clean and prep chemicals, and follow up with their sealant coating. The whole process will take days, not hours, but really works well if done properly.

I'm lucky in that I have access to 37% fuming hydrochloric acid that is very aggressive against rusty ferrous metal, but is not destructive beyond that when used properly.

You can also use the process of electrolysis to remove interior tank rust, but it will require that you submerge the whole tank and possibly sacrafice existing paint, but will not be effective unless old sealants are first removed.

If you believe Kreem elastomers were used to seal your tank, then contact them for proper method to remove same or simply buy a replacement tank off eBay.

P.S. I'm a commissioned Boiler Inspector who daily inpects ferrous metal pressure vessels-many of which are lined/coated to protect against corrosion. Trust me that eventually your tank will require weld repairs and are more cheaply replaced than repaired...Also know that a new untreated/sealed tank won't last long once gasoline is introduced. Gasoline has a very high vapor pressure that breathes twice each day. The tank will inhale moist air each evening, and then exhale each sunny day where the moisture remains and condenses then drops to the bottom of the tank to attack untreated steel very quickly. The rapid result is rust pits thru the tank wall and gas leaks on a hot engine. Water also contains dissolved 02 that quickly attacks unprotected ferrous steel like a termite eats wood.

Scooters kept indoors and not driven to work where they are not left out in the sun daily are less likely to exhibit this problem....For those scoots driven each day, a sun shield/cover over the tank will slow the process.

Car and truck gas tanks are not exposed to direct sunlight and heat like scooter gas tanks so they tend to last longer because less water and dissolved 02 is collected....If you have a black scoot that sees daily sunshine, then be concerned, but all color scooters left in the sun each day are eventually subject to same.

 

After you get the tank cleaned out, i'd suggest recoating it with a product called "por 15", it's much more durable than kream, easier to apply, and more forgiving with surface imperfections. I was turned on to the por 15 brand about 15 years ago when rebuilding an old BSA, and talked with a bunch of guys who specialize in refurbishing antique cars who suggested the stuff. And i've been very pleased with the product, I recently flushed out the bsa tank in july and the coating looked exactly like it did when I put it on.

 

Thanks for the tips, guys. A couple of soak/rinses with acetone did the trick. I'm treating it with Ospho-type stuff as we speak.