Topic: Beating Flash Rust on 5 Gallon Tank?

[BucNastyflo]

I have read every single thread re: tank rust/flash rust/vinegar and could not find any info on the best way to combat flash rust when draining a 5 gallon tank.

My K8 tank is currently on Day 3 of a vinegar soak filled to the brim. I can see lots of the rust particles floating to the top already. Some of the vinegar that flowed over the brim flash rusted the top of my gas cap hole in less than 30 seconds. Yikes!

My concern is the amount of time it takes to drain all 5 gallons of vinegar out, will the top of my tank already be flash rusted by the time I drain the vinegar out? I plan on adding the baking soda/water solution immediately, but I assume I must wait until all vinegar is out before doing so. I was curious if anyone had any special techniques or ideas on how to tackle this issue...

[BeSeeingYou]

Use phosphoric acid (Prep an Etch).  Just use if full strength to remove the corrosion.  I am not talking days here but 15...30...maybe 60 minutes.  It's not super aggressive.  Drain it and sop up any excess with a rag or paper towel on a coat hanger.  Don't rinse...let it dry in the tank and it will leave a protective phosphate coating that will not flash rust.

[TwoTired]

+1^^^

[mono]

Is a rust reformer like that ok to use a tank sealer on top of?

Sent from my SPH-L710 using Tapatalk 2

[TwoTired]

Yes.  Most tank sealers are a paint coating.  Which is exactly what prep & etch is for.

It is important to let the surface air dry after application.  This is what makes the coating rust resistant.  Use forced air if you can arrange it, I use a small computer fan, and let dry overnight. 

What sealer are you using?  Unless you have pinholes, I wonder if you need a sealer?

[bollingball]

Is a rust reformer like that ok to use a tank sealer on top of?

Sent from my SPH-L710 using Tapatalk 2

http://www.por15.com/CYCLE-TANK-REPAIR-KIT/productinfo/CTRK/
I have used this a lot on car tanks but not on my bike didn't need it. It works great. It is all in following directions to a tee no short cuts.

Ken

[jstfkndi]

I just did the vinegar trick on mine. I was not too concerned about paint or anything because it needs a new coat anyway, but with the vinegar, I drained it out through the top hole into a bucket poured about 1/2 cup baking soda in it dry and added wateruntil it was half full. Shook it up real well and repeated about 2 more times until the water came out clear (no reddish tint), After vigorously shaking out as much water as I could, I rolled about a pint of acetone into the tank and shook it around as well (this evaporates any remaining water) for about 3 minutes. You may not have to use as much as I did as Acetone evaprorates quickly and if you have to dump it out, then do so and coat with 2 stroke oil. I used about 6-8oz (again probably too much but it was my first experience with this) I would leave it open after coating with the oil for about 10 minutes to let any acetone you may not have gotten out to evaporate, but once it is coated, it is pretty set to go. I had to do other work while my tank sat, but when it came time to use it, I just rinsed it out with gas and filled it up for use Of course this is not prepping for a sealant and just using it bare metal after.

[skidooextreme]

using the phosphoric acid trick, do you have to apply a por-15 like coating or are you good to go? I am about to use the electrolysis trick on mine and just wondering if i still have to order the kit.....It has been sitting for 35 years, so you can imagine the rust inside(worried about pinholes too, but time will tell)

[BeSeeingYou]

If your tank is solid then no need for a liner...pinholes or weakened by corrosion yes.  Follow the directions on the liner product with no shortcuts or deviations is all I will say about that.

In addition to my previous post you don't need to fill the tank with Prep an Etch if you can take the time to flipping the tank around to slosh it around and keep the surfaces wet.

[Scott S]

 I use The Works toilet bowl cleaner method. After neutralizing with water & baking soda, I rinse with denatured alcohol (to help dy out any remaining water) and let air dry or use my air compressor, then add a couple ounces of Marvel Mystery Oil to coat the entire inside.

 I had an XS650 tank sit at the body shop for a year like this and it stayed cleaned. The MMO is safe to just add gas and run through the engine.

[mono]

This was on the "free table" at work the other day.  Active ingredient is phosphoric.  Anyone ever use it?

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[BucNastyflo]

I used the prep n etch method... worked like a charm.. unbelievable.

I let the tank drain and shot compressed air/heat gun combo to dry it. I did not rinse it at all.
Tank has dull grey film and no rust yet... Due to Sandy there is no gas in NYC so I cannot fill it up yet.

Should I rinse it out before putting fuel in? Will the dull grey coating come off and screw up my carbs? I am sending them out to be rebuilt so I wanna make sure I don't ruin them when they get back...

Thanks in advance.

Buc

[BeSeeingYou]

Just put gas in and go.  The tank I did this to is not in use but from what I have heard from a few other members is the phosphate film is still there a year later.  It is not thick like a tank liner.

[BucNastyflo]

ok perfect! thx for the reply!

[BucNastyflo]

So I just looked inside the tank and there is some rust forming again. 

I guess I need to fill it with fuel immediately after drying? or should I have used a baking soda and water solution to wash it out? 

[Scott S]

 The baking soda and water is just to neutralize ay remaining acid. You need to coat it with some type of oil if you're not putting gas in it fairly quickly. Marvel Mystery Oil, WD40, etc.

[jamesb]

I cleaned  few tanks. And I used oil gas mix to stop flash rust after the the acid cleaning I took a 1/2 quart oil and a 1/2 cup gas and sloshed it around in the tank. Drained it repeated that a few times and filled it with gas and didn't have any problems the oil coats the inside pretty good just need to keep gas in the tank.

[BeSeeingYou]

You don't neutralize Prep an Etch like you would with other acids.  Not sure what would cause the flash rust.  I have a battery box that was stripped of paint and treated with Prep an Etch.   It has been sitting in my basement for six months with no sign of rust.  The directions do say to paint the metal within 48 hours to prevent rust but I have not had a problem leaving it go much longer as long as you keep it away from water.  Don't know if using the heat gun would have any effect.  I just let mine air dry.

I have a heat vent grate (old house with big vents) in a bathroom I treated the same way and it has been in place for several months with no problems...I keep meaning to paint it but just don't get around to it.

[Jiminy Indy]

I've used the Works, but for me EvapoRust works great. It has no smell, is not toxic, won't strip your paint, and when you're done it just goes down the drain - water soluble. Available at Tractor Supply.

I know lots of people don't coat their tanks after cleaning but I've never been so lucky. My problem was the area above the gas where the humity is the air started to rust the tank and small rust particles fell and gunked up my petcock when I went on reserve.

I've used Red Coat with success, but then again that's just me.

[BeSeeingYou]

I know lots of people don't coat their tanks after cleaning but I've never been so lucky. My problem was the area above the gas where the humity is the air started to rust the tank and small rust particles fell and gunked up my petcock when I went on reserve.

I've used Red Coat with success, but then again that's just me.

You obviously apply it correctly.  For every person like you there is another one that cuts corners or thinks it can just be slapped on over a rusty tank.  The problem is not the product it's people who can't follow through and do a proper job of it and that's why it often fails. 

[TwoTired]

I also use Prep & Etch in order to get that grey zinc phosphate coating.

It says allow to dry without rinsing after etching.  The fluids catalyze the chemical reaction to form the coating and it is self limiting.  However, if you dry it too fast, the chemicals can't create a consistent and thorough coating.  A heat gun could conceivably evaporate the water (the catalyst) before a proper coating can form.

I think most failures are due to trying to hurry the process, cut corners, and "improve" on the printed directions.  You don't want it to dry fast.  Slowly is better for forming the protective coating.  You do want it dry before you paint or add another surface coating over the prep process.
Heck I used the oft hated Kreem as an overcoat and sealant (pinholes). I also let it completely dry out with forced air circulation for 2 weeks before it ever saw gasoline. After 5 years, the coating was still fine and rust free.  Bike was then sold.  So, that's the end of the personal history on that one.

It also helps to NOT do your first chemical experiment on the tank you wish to save.  Find a piece of steel with rust, and experiment with that to gain confidence with the process.  Once you've learned what works, THEN apply it to the tank.

Cheers,

[BucNastyflo]

Very interesting...

I will do another treatment sans heat gun... Would shooting compressed air in there be worth it? I'm more than happy to let it air dry as it would be less work.

For those that used the Prep and Etch method... How long did you let it soak in tank? I was doing 15 mins as I was scared I may damage inside of tank if I left it too long.. Did you guys cut the P&E with water or straight up?

[BeSeeingYou]

Leave it in long enough to remove any corrosion.  I have soaked heavily corroded parts in it for an hour with no issues.  It's not that aggressive.  If you are just removing light surface corrosion or flash rust a short time should do the trick.  Diluting it is for etching clean metal to get it ready for painting.  If I have any corrosion I use it full strength.   I don't bother with any method to hasten the dry time.  But do try and soak up any excess left in the tank as it will leave a white residue.  Coat hanger and a rag like I said before does the trick.

[Jiminy Indy]

If you do decide to coat / seal the inside of your tank - which I certainly recommend - make sure you allow adequate time for cure. For the first two days I rotated the tank every now and again to make sure there wasn't any pooling of the sealant and used compressed air to keep the air circulating. I then waited a good month until I couldn't detect any solvent smell - then waited another two weeks for good measure before I mounted the tank and added gas. Been a couple of years and had no problems at all.

[bjatwood]

I just used this kit on a 1971 SL175 that had gas in it for over 28 years!!
I first used electrolysis to get the junk out, followed by the vinegar soak, baking soda flush.
Tank was very nice.
After 2 months the gas tank had flash rusted and turned the gas black!
So, I used this kit....http://www.por15.com/CYCLE-TANK-REPAIR-KIT/productinfo/CTRK/
problem over! Best 40 buck deal out there IMO. Tanks looks like it could withstand years of use now.
I got some of the tank coating on my fingers....Man it took over 10 DAYS for it to wear off my fingers 
Just imagine how well it will work on a tank surface...
Stepping down off the soap box now