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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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 Posted: Sat Jul 24, 2021 8:38 pm Post subject: Re: Do I need to re-coat fuel tank? |
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| Jason0115 wrote: |
| raygreenwood wrote: |
Yes...your original method is fine....just dont dilute the muriatic acid so much.
Other minor issue. Skip the leaf blower drying. You need the drying time factor. The surface needs time after both acids to react. Do not QUICKLY blow this dry. You can blow off heavy excess....but it needs to stay WET and dry naturally.
After the muriatic acid.....just a quick rinse with water ....shake out excess....let dry. The longer it dries....usually the more flash rust you get. If I dont get enough flash rust or its not even.....I acid wash again.....just a quick one.....then rinse....then flash rust time.
When you use the phosphoric acid.....same basic process but it NEEDS 24 hours of drying/reaction time. This is the mistake most people make with phoaphoric acid conversion.
A. They rinse it off. Dont do that.
B. they get in a hurry. It needs reaction time and it needs to dry hard.
There should not be any water rinse after the phosphoric acid and before this 24 hour dry period.
Once that 24 hour period is done....look into the tank for blackish blue converted metal and no visible rust. If that's the case....give it a quick rinse with water and install it and fill it up with fuel. Nothing special to be done.
Ray |
I appreciate the help. I got all the chemicals and I rinsed out the rest of the gas in the tank with hose. But once I rinsed it out, I almost feel like for the amount of very light surface rust I might not do all of this right now and just put the tank in and check my filters to make sure nothing bad is coming through. I felt the tank with my finger and it is smooth not rough or anything where you can see the visual rust. Here’s another video of the tank rinsed out, do you think this small amount of rust is a concern if I just put it back in and go with it? It looks very insignificant but I know rust doesn’t sleep. I also am running a carb not FI system.
https://youtube.com/shorts/qE_d2Tj_oVI?feature=share |
And in a fuel tank....you can get away with "some" surface rust. The problem is that rust entrains oxides with its own oxygen supply. It continues to rust a little....very small amount. However along with the ethanol we have these days which carries oxygen....you can get more rust.
The object of this whole thing is two-fold.
1. Get it fairly smooth even if its surface rusted. Total thickest rust spot down at about 0.003" or thinner. No crusty stuff.
2. Neutralize the surface rust. MOST IMPORTANT...because its STOPS what I was speaking about above.
#1 is important because phosphoric acid properly diluted....can only neutralize about 0.003" thick at the deepest.
#2 is important because even at 0.001" to 0.002" thick rust...will keep growing of not neutralized.
If you have the tank out....and you believe its smooth enough....just throw some vinegar in and slosh it around...rinse and let it sit. It will surface rust Acid is acid. Then just neutralize and wait over night. Done.
Its not that hard....and you will be kicking yourself a couple years down the line if something starts choking your filters and...because you did not neutralize ....you have no idea for SURE....that its not crap in the tank. 
Ray |
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Jason0115
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Joined: April 11, 2021
Posts: 97
Location: New Jersey
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| Posted: Fri Jul 30, 2021 12:32 pm Post subject: Re: Do I need to re-coat fuel tank? |
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| raygreenwood wrote: |
If you have the tank out....and you believe its smooth enough....just throw some vinegar in and slosh it around...rinse and let it sit. It will surface rust Acid is acid. Then just neutralize and wait over night. Done.
Its not that hard....and you will be kicking yourself a couple years down the line if something starts choking your filters and...because you did not neutralize ....you have no idea for SURE....that its not crap in the tank.
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So I think I did this wrong. I used vinegar, it cleaned it well and surface rusted over the old spots so that was fine. Then, I used 2qt phosphorous solution (3:1 phosphorous to water) and over a 24 hour period, I would swish it around and lay the tank on different sides to get it even. After this 24 hrs, it looked like it worked inside. At this point, it is photo 1. Looks silver, black and blue. But then after this, I emptied the solution and let it dry/harden for another 24 hrs which is today. Then, the tank got all yellow, white, and crusty looking as you can see in photo 2. It feels smooth on the inside. I rinsed with water, blew dry and coated with gas and lucas just so it doesnt rust. What did I do wrong, I don't think it should have turned looking even worse than I began with. Can I put it in from the looks of the second photo, or should I repeat and do something different? I don't know where to go from here.
Photo 1 (24 hrs after phosphorous solution in tank)
Photo 2 (24 hrs after I emptied solution and let dry, looks worse on other side)
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raygreenwood
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Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Fri Jul 30, 2021 2:00 pm Post subject: Re: Do I need to re-coat fuel tank? |
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OK...everyone read closely!  Everyone makes the same mistakes!
The object of my long answers is NOT so you will just follow directions....but so you understand why and how each step works. If you do not fully understand this.....it will not work as well or may not work at all...because you will have....the natural tendency .....to act on the voice in your head telling you....."if a little is good...more is better!"
This stage was done perfectly!
| Quote: |
| So I think I did this wrong. I used vinegar, it cleaned it well and surface rusted over the old spots so that was fine. |
This stage was done wrong. Not horrible...but let me tell you what this does.
| Quote: |
| Then, I used 2qt phosphorous solution (3:1 phosphorous to water) and over a 24 hour period, I would swish it around and lay the tank on different sides to get it even |
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1. If you are trying to REMOVE...ALL RUST....down to metal, you can use EITHER muriatic acid or phosphoric acid.
Rules: how well either acid works is directly dependent on "TIME"...and solution strength.
1. If you use full strength phosphoric....it will remove all rust and convert nothing
2. If you use either full strength or diluted muriatic acid...it will remove all rust and convert nothing. This is because A. its a stronger solution strength acid than phosphoric and B. because its an oxidizing acid and it cannot convert rust.
3. Even if both muriatic acid or phosphoric acid are diluted.....if you have enough of it (volume so it does not get depleted by reacting with the metal) and you leave it on long enough....it will remove all rust and convert nothing. Thats the "time factor"
What you did wrong....was number 3
You put in a good amount f phosphoric acid......and even though it was diluted....you kept it in there and going all night long.
The PROPER way to do it.....was to pour in a quart maybe less of diluted phosphoric (which you did)....slosh it around to cover all surfaces just so they are wet. It will soak in and try to dry a little. Give it one more quick rinse with phosphoric acid....and then..... POUR IT OUT...and let it air dry for 24 hours.
Its not really a hardening process. The acid needs to react.....and then CHANGE STATE from liquid to solid...in its reacted state....to leave behind a layer of iron phosphate.
| Quote: |
| After this 24 hrs, it looked like it worked inside. At this point, it is photo 1. Looks silver, black and blue. |
The silver...is bare metal. Not what you want. The black...is iron phosphate...exactly what you want. The blue is somewhere in between and mostly teh polymer binder that is in the ospho
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| But then after this, I emptied the solution and let it dry/harden for another 24 hrs which is today. Then, the tank got all yellow, white, and crusty looking as you can see in photo |
The yellow...is actually very clean, fine surface rust.....that appears on the metal that was silver. Its actually a great candidate for using phosphoric acid on....if you use it correctly this time.
You got that yellow thin rust...because you left the phosphoric in so long it dissolved ALL rust on the surface leaving bare metal....which then surface flash rusted.
The white crusty stuff is a mineral/polymer residue. Its common. If you were going to paint something...it would be a mess. Its dried foam mostly from the ospho. Its not a problem as the fuel will dissolve it pretty quickly and it will be gone.
You are probably going to be fine. You have no real rust in the tank. The thicker crustier spots have turned black and converted.
If you wanted to do it over....lets keep this simple. Don't worry about what has already turned black...thats done right.
If you can degrease the tank easily with solvent and soap and water......do these steps only:
1. fill with muriatic acid and water....50/50. Slosh around...repeat...slosh around....about an hour. Drain. Rinse ONCE with water. Let dry for 24 hours. Do not TRY to dry it much....just lay it in the sun and let it dry. Inspect.
2. If not enough rust but lots of silver metal.....take a quart of water with about 6 oz of muriatic acid and slosh it all around and drain. Do not rinse...let dry. That should produce as much surface rust as you are going to get.
3. Take diluted phosphoric acid...abut a quart. Slosh it all around for about 15 minutes. Get everything wet. Every surface. Pour it out.
DO NOT RINSE it. If you have a lot of foam on the surfaces inside....use an air hose to splatter the foam bubbles and break them.
Or....I use a kitchen sponge or a foam paint brush on a long stick...wet with diluted ospho...to drag over the foam to pop the bubbles.
Let it dry for 24 hours.
4. It should be done. Do not rinse it...just fill it up with fuel or oil it and store it. Ray |
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aeromech
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Joined: January 24, 2006
Posts: 16961
Location: San Diego, California
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| Posted: Fri Jul 30, 2021 2:18 pm Post subject: Re: Do I need to re-coat fuel tank? |
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That radiator shop must be sounding pretty good about now 😁
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Fri Jul 30, 2021 6:41 pm Post subject: Re: Do I need to re-coat fuel tank? |
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| aeromech wrote: |
| That radiator shop must be sounding pretty good about now 😁 |
Well....understand....  ....we are doing two different things. If you just want it shiny and bare metal....and you have a radiator shop close by. Do that by all means.
However....that now means that you will have to do it RIGHT this time. Keep the tank above half full. Keep the water out of it. Avoid ethanol as much as possible because it accelerates corrosion.
Sure....it may take another 10-20 years to start getting bad crusty rust again....but the next time around there may not be much left of the tank and will damn sure be a ton less spare fuel tanks around.
On this side...we are killing the rust and/or getting rid of it....and then putting an anti-rust treatment on the tank inside. If its done right...just basic care it will likely never rust again. Ray |
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cmonSTART
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Location: NH
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aeromech
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Joined: January 24, 2006
Posts: 16961
Location: San Diego, California
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| Posted: Sat Jul 31, 2021 6:39 am Post subject: Re: Do I need to re-coat fuel tank? |
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Aftermarket parts like these have a bad habit of coming back to haunt you. It seems like in this day and age buying a part like that that works well right out of the box is rare
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
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cmonSTART
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Joined: July 15, 2014
Posts: 1915
Location: NH
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| Posted: Sat Jul 31, 2021 7:25 am Post subject: Re: Do I need to re-coat fuel tank? |
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| aeromech wrote: |
| Aftermarket parts like these have a bad habit of coming back to haunt you. |
So does cleaning up rusty steel. 
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Sat Jul 31, 2021 7:58 am Post subject: Re: Do I need to re-coat fuel tank? |
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| cmonSTART wrote: |
| aeromech wrote: |
| Aftermarket parts like these have a bad habit of coming back to haunt you. |
So does cleaning up rusty steel. |
Not if its treated....which is the whole point of this.
Ray |
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Jason0115
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Joined: April 11, 2021
Posts: 97
Location: New Jersey
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| Posted: Mon Aug 02, 2021 10:24 am Post subject: Re: Do I need to re-coat fuel tank? |
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| raygreenwood wrote: |
1. fill with muriatic acid and water....50/50. Slosh around...repeat...slosh around....about an hour. Drain. Rinse ONCE with water. Let dry for 24 hours. Do not TRY to dry it much....just lay it in the sun and let it dry. Inspect.
2. If not enough rust but lots of silver metal.....take a quart of water with about 6 oz of muriatic acid and slosh it all around and drain. Do not rinse...let dry. That should produce as much surface rust as you are going to get.
3. Take diluted phosphoric acid...abut a quart. Slosh it all around for about 15 minutes. Get everything wet. Every surface. Pour it out.
DO NOT RINSE it. If you have a lot of foam on the surfaces inside....use an air hose to splatter the foam bubbles and break them.
Or....I use a kitchen sponge or a foam paint brush on a long stick...wet with diluted ospho...to drag over the foam to pop the bubbles.
Let it dry for 24 hours.
4. It should be done. Do not rinse it...just fill it up with fuel or oil it and store it. Ray |
Ok, so I did exactly as you said here to the dime. My phosphorus was 1/4 water 3/4 phosphorous diluted. I got more surface rust this time after the muriatic acid bath. The tank still has a lot going on inside it after about 17 hours of drying after the last step. It will be 24 hr soon after posting this. Mostly the dried foam some yellow some black and some red orange spots. I’m not sure if I didn’t have enough rust to start or didn’t dilute the phosphorous enough but I followed exactly as you said. I thought there was enough surface rust after the muriatic acid. Maybe the tank is fine now idk. I think I might just put it in at this point and check my filters often. I’m not getting it on the road any time soon but I wanna get my engine back together. Any ideas and how do you feel about these pics?
Thanks for all the great responses everyone.
I couldn’t upload for some reason so I put the new pics in a google drive folder here:
https://drive.google.com/drive/folders/1-3peXZhKv7q1gfiomDPKMnL4WaXsH6yy
Last edited by Jason0115 on Mon Aug 02, 2021 11:42 am; edited 1 time in total |
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cmonSTART
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Jason0115
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Joined: April 11, 2021
Posts: 97
Location: New Jersey
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| Posted: Mon Aug 02, 2021 11:42 am Post subject: Re: Do I need to re-coat fuel tank? |
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That’s my backup plan! |
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raygreenwood
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Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Mon Aug 02, 2021 2:01 pm Post subject: Re: Do I need to re-coat fuel tank? |
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| Jason0115 wrote: |
| raygreenwood wrote: |
1. fill with muriatic acid and water....50/50. Slosh around...repeat...slosh around....about an hour. Drain. Rinse ONCE with water. Let dry for 24 hours. Do not TRY to dry it much....just lay it in the sun and let it dry. Inspect.
2. If not enough rust but lots of silver metal.....take a quart of water with about 6 oz of muriatic acid and slosh it all around and drain. Do not rinse...let dry. That should produce as much surface rust as you are going to get.
3. Take diluted phosphoric acid...abut a quart. Slosh it all around for about 15 minutes. Get everything wet. Every surface. Pour it out.
DO NOT RINSE it. If you have a lot of foam on the surfaces inside....use an air hose to splatter the foam bubbles and break them.
Or....I use a kitchen sponge or a foam paint brush on a long stick...wet with diluted ospho...to drag over the foam to pop the bubbles.
Let it dry for 24 hours.
4. It should be done. Do not rinse it...just fill it up with fuel or oil it and store it. Ray |
Ok, so I did exactly as you said here to the dime. My phosphorus was 1/4 water 3/4 phosphorous diluted. I got more surface rust this time after the muriatic acid bath. The tank still has a lot going on inside it after about 17 hours of drying after the last step. It will be 24 hr soon after posting this. Mostly the dried foam some yellow some black and some red orange spots. I’m not sure if I didn’t have enough rust to start or didn’t dilute the phosphorous enough but I followed exactly as you said. I thought there was enough surface rust after the muriatic acid. Maybe the tank is fine now idk. I think I might just put it in at this point and check my filters often. I’m not getting it on the road any time soon but I wanna get my engine back together. Any ideas and how do you feel about these pics?
Thanks for all the great responses everyone.
I couldn’t upload for some reason so I put the new pics in a google drive folder here:
https://drive.google.com/drive/folders/1-3peXZhKv7q1gfiomDPKMnL4WaXsH6yy |
Which phosphoric acid product are you using?
You will probably be fine....but it looks like the run off from the phosphoric is strong enough to remove rust rather than convert it.....in some areas....and in other areas it looks like it has not converted at all.
I think that will be fine. Some of what is on there will be a surface protective polymer that is in many of the phosphoric products.
The reason I ask which phosphoric product is that I have found a lot of variation from product to product and even lot to lot in the last couple of years. Ray |
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Jason0115
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Joined: April 11, 2021
Posts: 97
Location: New Jersey
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| Posted: Mon Aug 02, 2021 2:26 pm Post subject: Re: Do I need to re-coat fuel tank? |
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| raygreenwood wrote: |
Which phosphoric acid product are you using?
You will probably be fine....but it looks like the run off from the phosphoric is strong enough to remove rust rather than convert it.....in some areas....and in other areas it looks like it has not converted at all.
I think that will be fine. Some of what is on there will be a surface protective polymer that is in many of the phosphoric products.
The reason I ask which phosphoric product is that I have found a lot of variation from product to product and even lot to lot in the last couple of years. Ray |
I’m using Klean Strip Concrete and Metal Prep. Maybe I should try ospho ? although if I will get similar results I think I’ll just keep it as is and hope for the best.
It does seem as the prep & etch removed some of the rust due to its strength because before I drained it, it seemed like there was a lot of clean metal after the 15 min period (yellowish white and silver wet metal mostly and some foam). I have a feeling I should have done maybe a 50/50 dilution instead of 75/25 |
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Jason0115
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Location: New Jersey
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| Posted: Mon Aug 02, 2021 6:17 pm Post subject: Re: Do I need to re-coat fuel tank? |
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| Or I might take even more diluted etch & sketch and do another 15 min slosh 24 hr dry to hopefully convert the new surface rust. |
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raygreenwood
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Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Mon Aug 02, 2021 7:25 pm Post subject: Re: Do I need to re-coat fuel tank? |
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| Jason0115 wrote: |
| Or I might take even more diluted etch & sketch and do another 15 min slosh 24 hr dry to hopefully convert the new surface rust. |
I "think"....that is what the issue may be. Its just too strong. I say this because ....when I first started working with Phosphoric acid products....all I had or could find.....was basic Ospho in the green quart bottle. It worked well but was a little weak.
What I mean by that is that if you were doing a big piece...like a gas tank...and you put in too little like a little less than a quart...and there was a lot of surface rust or crust....it would kill off the ospho too quickly as it reacted.
As it reacts it gets depleted. This is also why they say on the bottle to never put used or partially used solution back in the bottle. it will kill it.
BUT....when I moved to Jasco prep and prime....I found that it was easily 3-4X stronger than Ospho. It had to be heavily diluted to not "act" like muriatic acid.
I think that is what is happening with your product. On the SDS....they specifically note that the percentage of Phosphoric acid is between 30% and 60%...and that the specific amount is not disclosed as a trade secret.
What I would like to see....it will help you and others....is find ...or make....a piece of rusty metal. Just a strip of steel. You can wire brush it off...degrease it with carb cleaner and soak it for 20 minutes in muriatic acid. Then rise...and let it rust the crap out of itself.
take a couple of thimbles or bottle caps full of your Kleen strip....mix it 3:1, 2:1 and 1:1 and then 1:2.....phosphoric / water....put a wet spot the size of a nickel of each one. Let them sit for maybe 10 minutes. Then just blot off any huge excess leaving them damp....and let them dry and see what you get.
Ray |
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Jason0115
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Posts: 97
Location: New Jersey
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| Posted: Wed Aug 18, 2021 4:41 pm Post subject: Re: Do I need to re-coat fuel tank? |
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| raygreenwood wrote: |
take a couple of thimbles or bottle caps full of your Kleen strip....mix it 3:1, 2:1 and 1:1 and then 1:2.....phosphoric / water....put a wet spot the size of a nickel of each one. Let them sit for maybe 10 minutes. Then just blot off any huge excess leaving them damp....and let them dry and see what you get.
Ray |
I tried this on a piece of VERY rusted metal (only piece I had laying around) and I couldn’t tell a difference but I tried on some rusted bolts and I found the 1:1 seemed to turned the most black. So I went with that for the tank, put a 1:1 solution into the tank without muriatic before since there was plenty surface rust from the last time, 15 min, drain, dry. Results were the best this time around. Mix of orange/yellow surface rust, bare metal, black and whiteish film but surface was smooth. I swished with fuel and Lucas oil then drained and filled with a few gallons gas. This is what I put in my bus, and I’ll be checking filters often and post updates. I’ll attach a picture when I get the chance of the inside of tank. I’m not completely satisfied but I feel like it should be ok.
I’m going to retry this test and get a better piece of metal to rust and try the phosphoric on. I’ll post those results here im interested to see how they turn out but I think 1:1 is a good baseline. |
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