Stainless petrol tank, avoiding water inside? Corrosion?

[Franziska]

Hi,

we just installed a new stainless petrol tank for our two Yamaha outboards.

Previously we had a plastic tank, but I like the stainless much more. It's in its own compartment without any electrical appliances in it.

Question though, how do we avoid contaminated petrol when filling it?
I am concerned about crevice corrosion at the bottom.
There is no bottom drain, as this is not permissible on petrol tanks.

The supply line to the engines has a centrifugal water separator, so that is less of concern.

We are on a budget, and in the past I have used one of those yellow plastic funnels with screen to help with it.
Still, the capacity of these is not a match to what comes out of the nozzle at the pump.

We have 120l capacity and that would make for a slow fill.

Suggestions? Preferably DIY, low budget abd/or out of the box thinking.
Am I overly concerned about this?

[rslifkin]

If you're using gas blended with ethanol, the tanks will stay dry on their own as there's a decent bit of water absorbing capacity built in. With my aluminum tanks, I periodically add some drygas (isopropyl alcohol) to soak up any moisture when running non-ethanol gas.



I'm not sure if you can get them in Germany, but I have seen big, multi-filter funnel setups meant for higher flow (Mr. Funnel is one brand).

[Franziska]

Originally Posted by rslifkin

If you're using gas blended with ethanol, the tanks will stay dry on their own as there's a decent bit of water absorbing capacity built in. With my aluminum tanks, I periodically add some drygas (isopropyl alcohol) to soak up any moisture when running non-ethanol gas.



I'm not sure if you can get them in Germany, but I have seen big, multi-filter funnel setups meant for higher flow (Mr. Funnel is one brand).

Hey, thanks, learned something. I usually use E10 so there is Ethanol in there.

We have something similar to Mr. Funnel, but I am glad to see that they come in bigger sizes too, just what we need.

[Compass790]

You can get tank liner coatings that work good, just google it
But here is one type.https://kbs-coatings.co.nz/products/...30214835241013
Some tanks in industry get coated inside with epoxy so if you have leftover resin that would do it but you have to have a clean, degreased tank.

[Lepke]

Water or fuel, any good tank coating, properly done, will last the life of the tank. A coated tank should last the life of the boat.

[Franziska]

Hmmm. Not sure I want to coat a never used stainless tank with something that can fail and break of later.
Don't get me wrong, I'm just not sure if I risk things like crevice corrosion or similar than.

To coat or not to coat that is the question?!

One more, if we were to coat it, we can not sand the inside of the tank before. We could perhaps do an Aceton wash or similar.
Will the blank stainless be enough for such a coating to adhere to?

[rslifkin]

My aluminum gas tanks are still in good shape after 35 years. As long as your tanks are well mounted and stay dry inside and out, I'd expect them to last a very long time without coating unless something flexes them enough to cause stress cracks in the welds.

[Franziska]

Thanks.

I think we will focus on keeping it dry.

The tank is very firmly strapped into its base and slightly raised as to not sit in any water.
It not located in a bilge, which helps too.

Flexing should not be an issue but we will observe it.

[BTAkers]

I have had great experience with Heet brand water remover. It takes a small amount in every fill up to keep the water out of your tank(and engine) and it cleans the fuel system

https://shop.advanceautoparts.com/wc...2_pri_larg.jpg

[Compass790]

Originally Posted by Franziska

Hmmm. Not sure I want to coat a never used stainless tank with something that can fail and break of later.
Don't get me wrong, I'm just not sure if I risk things like crevice corrosion or similar than.

To coat or not to coat that is the question?!

One more, if we were to coat it, we can not sand the inside of the tank before. We could perhaps do an Aceton wash or similar.
Will the blank stainless be enough for such a coating to adhere to?

Yes I can understand your concern about a coating adhering to polished stainless.
I cannot remember what they did for surface prep on polished ss tanks when I used to build them as they were sent out for coatings & coating ss is rare.
If its any help i'm fairly certain that our 1980 boat has the original uncoated ss tank in it & it does not leak & I know its had heaps of water thru it as the P.O. had no o-ring on the deck fuel fill cap. It's a diesel tank on our boat but I think you are worrying too much if the only water you get in there is fresh & the tank was made from 316L, purge welded.
Tank may well outlast you uncoated.

[fourlyons]

In the latest issue of Professional Boatbuilder, Steve D'Antonio has an article about fuel tanks. He comes down adamantly against tank coatings due to the real difficulty of properly prepping the surface well enough.

[Disailor]

I replaced an 18" section of the breather vent hose with a clear plastic tube with water absorbing granules to dry the incoming air. No water issues for years now.

[Franziska]

Originally Posted by Disailor

I replaced an 18" section of the breather vent hose with a clear plastic tube with water absorbing granules to dry the incoming air. No water issues for years now.

That's a great idea. Do you need to dry these granules from time to time?

[Franziska]

Originally Posted by fourlyons

In the latest issue of Professional Boatbuilder, Steve D'Antonio has an article about fuel tanks. He comes down adamantly against tank coatings due to the real difficulty of properly prepping the surface well enough.

Thanks, that's helpful, I will read it.

[Cheechako]

The biggest problem I see in SS tanks is what they are in contact with on the outside. If just resting on a surface, they stay wet and corrode fast where that support is. The water becomes low oxygen. SS would not be my choice for tanks. One bilge tank I had had holes the size of a pencil eraser no where near the corners or welds after 6 years. This tank was resting on a 2" type of wood/fiberglass. That's exactly where it corroded through.
Welds can be an issue from the inside occasionally, poor welding can leave a gap where the plates meet because the weld didn't penetrate leaving a big crack/seam perfect to start corrosion or vibration cracking..
The other issue is the welded seams if they are in a spot where they stay damp.

If you use the diesel regularly I would not worry about water inside the tank.