Rusty fuel tank

[MsRose]

I recently filled my old fuel tank with water to make sure there were no leaks before I began to restore it, but appears that leaving it in the sun didn’t let it dry properly, and now I have surface rust inside.

Am I able to swill round some kind of rust inhibitor inside from say a plumbers merchants, then swill out with petrol?

The tank probably won’t be fitted for a number of months and I really want to save it.

Advice appreciated

[Classiccars]

Not an expert but people use marbles chemicals or stones etc to clear the rust out.There is a sealer thst you can put in the dry tank to stop the rust starting again.Probably easier to pick up a good used one but would it be rust free is the problem.

[firedrake1942]

try and salvage it as the new ones dont have a drain plug

[Bill_qaz]

Be careful if you use tank sealer as many react with ethanol in current fuels.

[geoberni]

I recently filled my old fuel tank with water to make sure there were no leaks before I began to restore it, but appears that leaving it in the sun didn’t let it dry properly, and now I have surface rust inside.

Am I able to swill round some kind of rust inhibitor inside from say a plumbers merchants, then swill out with petrol?

The tank probably won’t be fitted for a number of months and I really want to save it.
Advice appreciated

I guess it really depends when you did this and how much surface rust there is.
Assuming it's just a bit of light rusting/discolouration , I would get an off the shelf rust remover solution, one that's 5L for about £15, and as you say, give the tank a good swirl around and soaking in it for the required time.

Most of them then say to rinse with clean water.
After doing that, thoroughly drain and dry it with an air blower or hair dryer to ensure it's dry.
Then before storing it, get some silica gel granules (about £9 for 500g on fleabay and it's reuseable) in an old shirt sleeve or similar which you can put in/out the tank via the Sender Unit hole.
Hang that inside and seal up all openings with tape until you need it.

Some might advocate use Citric Acid, but that needs to be done carefully or it can cause problems with the metal under the rust.

[svenedin]

try and salvage it as the new ones dont have a drain plug

Yes and this is annoying. I didn't even notice until I wanted to drain the tank.

Stephen