flash rust in tank

[exeric]

I have a freshly painted BT OHV tank that has flash rusted inside in spite of my efforts to tape off the openings. Obviously, Florida humidity got past my attempt to keep overspray out of the tank but I overlooked steel's worst enemy. I can easily remove the rust without paint damage, but my question is: What would members recommend for protecting the bare steel inside the tank until it's holding gasoline again? Would sloshing it with oil be sufficient, or is there a better product? Thanks

[pisten-bully]

Eric, great question and thanks for posing it! (I see you have this post doubled up, so I picked the one with most views to reply to )

I want to hear ideas folks have!

[Lyle Manheimer]

Metal Rescue had a product available to prevent flash rust. I had a sample but I never tried it. I do know their rust remover works very well and if used as directed have never had a problem with paint damage.

[chuckthebeatertruck]

I’m so glad I don’t have to fight high humidity.

my usual go to has been dissolving atf or marvel mystery oil in mineral spirits at 1:1 or 2:1. Slosh around well and drain. The mineral spirits shouldn’t harm cured paint, but carry the oil well. It’s thin enough to get everywhere but thick enough to create a film. It also “dries” to some extent and doesn’t attack rubber gaskets in the filler cap, etc. When filled with fuel, it burns off with little smoke.

In the future, you can toss those silica gel packs in your tank. When off the bike it’s easy to shake them out. Just don’t fill the bike with them still in there!

[Jerry Wieland]

Molasses will remove rust without damaging metal or paint. Maybe search that topic on this forum. Similar products are also offered commercially. Jerry

[Skirted]

I have use Sta-Bil fogging oil to protect tanks during empty non-use storage. I don't have any data to prove how well it works but since it is designed to protect internal cylinders in engines from corrosion in long term storage, it always seemed like the perfect product for tanks.

[knuckcrazy]

Ospho will dissolve the rust and leave a black coating similar to Parkerizing.

[Chris Haynes]

Keeping your tank full will prevent further rusting.

[Bob W]

Phosphoric acid etchant sold as concrete or metal etch at Lowes converts rust to a grey coating. Some body suggested using a very heavy coating of wax on the paint before using any chemical in the tank. It seems to work. Unlike masking liquid did not get under it

[exeric]

I use muriatic (swimming pool) acid, molasses, vinegar, and off the shelf rust removal products and they all work quite well. However, flash rust is always the problem with any kind of rust removal and it is a problem that occurs within minutes of using any rust killing product. I was most curious if anyone had a process that they use after de-rusting that will minimize the immediate flash rust. I am well aware of Ospho but I'm concerned about the white powdery bi-product of it use and if it is a potential problem.

[Peter Cooke]

I use Ranex on everything that comes back from bead blasting. And gave the insides of my tanks a dose as well. Works really well and just needs the usual paint preps when the time comes.
Not sure if it's available in the US but there's gotta be something similar.

Bondall Ranex Rustbuster

[Steve Swan]

Eric, i know exactly what you mean about flash rusting appearing SO quickly...

i've used different rust removal approaches depending on the nature/severity of the rust, and have settled on reverse electrolysis and/or 3% H3PO4 sol'n. when neither completely removes the rust, i resort to a quantity of 50, 1/2" and 9/16" nuts loaded into the tank, then rotated for a cycle or two in the clothes dryer, i am always surprised what comes out of the tank after a cycle or two in dryer.

That being said, when using either rust removal approach, i quickly rinse with cold water running at copious amounts until clear, empty the water, then quickly add a quart of acetone to dry things out and then add a pint of engine oil, hand rotate the tank and empty the remainder; my method seems to prevent flash rust. i am curious about Skirted's use of Stabil Fogging Oil which seems like that could well be a better choice than engine oil.

i've experimented with different other types of rust remover, i.e., wood acid, evaporust, metal rescue, molasses, and after such experimentation, in my experience 3% H3PO4 soln and/or reverse electrolysis work best for me.

i agree with keeping the tank full of gasoline is good practice, but not gas with ethanol which absorbs moisture from any air remaining in the tank despite the tank being full; there's always going to be at least some air in the tank unless it is filled to the point before overflowing. my experience is that moisture tends to condense on the on the under surface top portion of the tank. i've had some tanks have pinholes show through on the top of the tank after i've removed the rust.

just my 2 cents...