Restoring Gas Tank

Hey guys,

So I bought a 1981 550 seca gas tank (lucky me these seem to be getting harder to find) that is extremely rusty on the inside, and not too bad on the outside. I'm planning on restoring the inside and repainting the outside though so the condition isn't a big deal anyway.

I originally tried cleaning the inside with the distilled water and sand method, but holy **** what a work out that was. I shook that thing in every direction possible for at least 30 minutes. By the time I gave up I looked up to see my neighbor starring at me from across the yard. I cant imagine what was going through his head.

Once I decided I had enough of that I decided to go get some evapo-rust. I followed the instructions and tilted the gas tank on each side and the front and back for an hour each, shaking it a little between each turn. Then i dumped the contents, by this time it was dark outside so I couldn't tell what color the fluid had become and I then cleaned it with detergent and distilled water. I brought it inside the garage, shined a light into it, and to my disappointment it still looks like hell (see pictures).
(First is from the gas cap hole, second is from the float hole)

I was hoping someone might have some insight into a better way to clean this. Has anyone ever gotten every bit of rust off the inside as far as you could tell? Ideally I would like this thing to look brand new on the inside, but realistically at what point do I stop and just re-line the inside of the tank?

 

Phosphoric acid about 10-15% conc. lots of threads here on tank resto. To avoid flash rust you need to follow your water rinse with an alcohol flush to trap water that will be sitting in crevices

 

I have had great luck with White Vinegar, @ $2.64 a gal just fill it up to the top of the tank. Let is sit with a little rocking action now and then for a week. It will get rid of the rust and also take care of all that brown nasty stuff as well. I can't tell from the pics if that rust is so bad that it will or has rusted through.

Rinse the heck out of it, rinse it with good pressure until no bits are coming out with the rinse. I don't use a sealer on my tanks because I have had the sealer start to come loose. It could have been me but it might have been the ethanol in the gas in my area. I just don't take the chance anymore. Getting all the water out is the way to go and to make sure you don't get flash rust in there. I also mix a little gas and some Mystry oil together and make sure I swish it around all the spots of the tank.

A in-line filter will be needed at least for the first tank of gas or for the rest of the time you use that tank, just to make sure nothing gets in the carbs.

 

I will definitely look into that thank you

 

For $2.46 to try vs the $30 dollars I spent on evaporust its definitely worth a shot. How rusted was your gas tank when you tried this?

 

No disrespect to Timbox but your rust seems like it needs a bigger hit than vinegar which is typically low acidity, also bear in mind that using phosphoric converts rust to inert, black, iron phosphate and is the main ingredient in (most) anti-rust preparations (although not Evapo-rust I understand).

 

Clean it out well with acetone first, looks like there is some lacquer on the inside surface. After that dries fully fill it up with Evaporust completely and let it sit for 24 hours. You'll need to flip it once at least to prevent an etch line since the tank can't be filled absolutely full.

 

put it in the drier and use drier like a rock tumbler. bag and pad well you can use small fish tank gravel. the info overload has many methods from electroless to chem treatments

BB's work well and being steel coated with copper can be removed with a magnet

 

your sand wasn't up to the task, try all your old nuts and bolts or a bunch of BB's then fish them out with a magnet

 

I've just removed the fuel sensor and dried out the inside. There is some crusty rust that still seems superficial. I made a cover for the fuel sensor opening. Leaving the petcock in since I'm replace it anyway. It'll give me a convenient drain. If what I use will dissolve the rust, I won't clog the screen on the petcock. Toying with going for the metal rescue directly.

 

Its all good, what even they want to do to the tank. I was just giving a cheap option. My way does take longer and I would guess phosphoric is the way to go, I might have to try it next time. If it works in 24hrs and you are in a hurry, that is the way to go.

 

siphon hose then open fuel sensor port rinse out with water hose blow dry and treat with 2 cycle oil to prevent flash rust

 

I pulled the petcock and threw in a handfull of M6 nuts I had laying around. I shook them around a bit, flushed with water, did it again and flushed, got the flaky rust out of the bottom. I then made another cover for the petcock hole and closed up the bottom of the tank and poured 1 gal of metal rescue in. I'll check in a couple of hours to see if the bottom is clean. If so, I'll rotate the tank and let it sit a few times to get the sides treated. It's a challenge to get the very top with the gas cap being vented, but I may just remove the gas cap and throw in a stopper to try treating the top side of the interior of the tank.
It sounds like once I drain that out, I ought to flush as much water out (maybe compressed air or a hot air gun), then wash with alcohol (will mineral spirits do?)
Sounds like throwing some 2-cycle oil in there to fight flash rusting is the last step. I assume throw in a few ounces and rotate the tank around till it's coated? Any better technique? How about a few shots of WD-40 in the top and up from the holes in the bottom of the tank? Might stand a better chance of getting an even coating.

 

alcohol mixes with water and lets it dry up faster,i don't think mineral spirits mix with water
a quart of pre-mix 2 stroke gas will get it coated, then when your ready just add fresh gas and go, xj's run great on pre-mix
it takes longer to dry those seams than you think

 

Let us know what your tank looks like afterwards

 

I'll have to look up from the bottom openings, but it seems like this tank doesn't have the same kind of seams the XJ tanks have. Basically, the front of the tank is an airbox cover and the rear is a 4 gallon tank where the bottom part is a single stamping. Makes for no seams at the lowest parts.
I've rotated the tank and it's on the side now. Rust is going away, bit by bit.

Someone told me mineral spirits were alcohol-based, but it looks like it's petroleum based. I'll go find some alcohol to help dry the tank after rinsing. I'll also mix some 2-cycle gas which I can use in the chainsaw after. There are some trees I've had my eye on in the back yard.

 

I case anybody is interested. I had some plastic sheet I cut to make blanks and cut a piece or rubber as a gasket to cover the openings.

 

No, mineral spirits is hydrophobic do not use it for drying. Acetone is even better than isopropyl alcohol since it evaporates faster, is very hydroscopic and will also dissolve all distillates of crude oil when rinsing.

 

I do have acetone on hand.

 

I got the majority of the rust taken care of. Some surface rust at the very top around the cap is still there and a little here and there, but it's a whole lot better than before. I can also vouch for acetone drying out the tank! I stuffed some blue shop paper towels inside and used a dowel to mop up the bottom of the tank. Then, I plugged it all up and dumped some acetone in. Closed up the tank and swished it all around. Drained it and then used the paper towel trick to get the last of it out. Metal inside looked bone dry! So, I dumped the can of 40:1 2-cycle premix in and swished it around and there it sits, waiting for carbs to be finished. I'll mix in some fresh 91 octane before I run the bike off the regular tank. (12:1 compression ratio, I figure higher octane is called for).

 

I've saved tanks that were rusted clear thr0ugh. Here's my method.
Tape up any holes that have rusted through. Gather up a sizeable
fistfull of steel nuts and dump them in. Cork off the fuel port and
block off the petcock hole. Pour in about 4 cups of phosphoric acid
from HD or a paint store. Protect yourself ( that's "acid" bro" )
Shake it up real good, until your arms get tired. Let it sit, then repeat
a bunch of times. Drain it into a bucket through a bug screen, so
you can use the acid again. Then mix a cup of baking soda into
a gallon of water and dump that in. Shake all of that up until your
arms get tired. Drain and follow up with clean water to flush out all the soda.
Now, fish out all the steel nuts with a flexable shaft pick up magnet
and let the tank dry in the sun. Change out the tape over the rust holes
and apply a good 2 part epoxy tank liner, following the instuctions
with exactitude, rotating the tank so that every inside surface gets covered.
It sets up in about 15 minutes. The kit I bought had enough epoxy for two coats.
Pull the tape off and cover where the rust holes were with resin and fiberglass.
Smooth out everything with bondo, sand and paint. Now you have a beautifully
restored tank and a fistfull of clean shiny steel nuts.

 

is the baking soda to neutralize the acid?

 

I just covered my openings with some plastic I cut from some old containers and put a bead of hot glue around the edges. About to fill it up with hydrochloric acid and water. I'll give an update tomorrow

 

hot glue and hydrochloric acid, Oh boy, i don't think such a good idea

 

Seems to be working fine for now

 

HCL is not usually the favorite as it will also eat the steel - does not form a passive layer like phosphoric. i.e. long term use will dissolve your tank completely.