Coating for SS fuel tank pitting...

[leftbrainstuff]

3

Originally Posted by UNCIVILIZED

The OP does. It's 2'x4'x5', thus 40cuft, & at 8gal/cuft, 320 gal.

leftbrainstuff,
In mentioning epoxy, I think that you're referring to something else. But when I mentioned epoxy, what I wss referring to, was completely encasing the tank in fiberglass & epoxy. It's an old technique, but likely still viable. And many a tank was built at the factory that way.
They've done it plenty with aluminum too.

Epoxy linings are on the inside of the tank. This is a standard engineering practice in many chemical processing environments. This way cheap non exotic materials can be used to build the tank / pressure vessel which carries the physical loads.

The epoxy lining provides the chemical compatibility needed. I've engineered these solutions for caustic, acids and plating chemicals.

If you epoxy coat the exterior you end up with corrosion issues. Especially with stainless and aluminum which both require exposure to oxygen to build and maintain their protective oxide layer. I would not consider exterior coating to be a good practice in this use case.

Exterior epoxy linings are used to dress up poorly fabricated metal tanks. Water softeners and calorifiers spring to mind.

There are about a dozen groups of industrial epoxy lining material specs which have varying chemical and temperature characteristics. Most will work with diesel.



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[petter5]

As used in the maritime industry:

Belzona 1331 spray or brush applied coating

/Petter

[HappyMdRSailor]

Originally Posted by UNCIVILIZED

Where are the baffles located in this tank? Assuming that it has some. Which, it'd be loco not to, given that it holds 320 gallons.
And the reason I'm asking, is that, where they are & their orientation & size; both governs, AND rules out some of the possible fixes.

Baffle orientation in pic... I'll post another with the four access holes cut... Appx 10"x10" for the large 3, 4x10 for the quadrant next to the sender...

Originally Posted by a64pilot

Wait a minute, who has a 320 gl tank?

240g with the angled in forward Mr. Pilot... That's an island queen

[HappyMdRSailor]

Originally Posted by Trekker

This is classic device corrosion and the long-term fix is to prevent moisture from getting trapped between the tank bottom and whatever it rests upon. There needs to be space enough to allow air to circulate between.

This is from the inside out... water pooling in the tank, and electro-galvanic-hocus-pocus

Originally Posted by leftbrainstuff

A sign of water in the tank.

If its just a few pits then TIG filling them with 308 wire works well. Can be done in situ if you can get access. A thorough steam clean is necessary.

I wouldn't bother double skinning in place. Horrible solution, expensive too in terms of labor.

Epoxy coat, internally, is a viable option. Fuel tank sealers too although I would consider that a last resort. Lots of ex military F111 maintainers, in Australia, suffering from very nasty cancers from fuel tank sealing.

If you epoxy coat you need to do the whole tank. Epoxy coating metal vessels in the process industry is common practice. Many excellent products are available.

If you can remove them or cut them out then a bladder or polyethylene tank(s) are viable. The plastic tank is the best option by far. Lots of shapes available from vetus, moeller and the like.

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Agreed... skinning the bottom is a terrible solution... I think I'll skip the individual tig filling... BUT... maybe a SS patch of the couple areas??? Likely to be only a few of about 4-6" square... Hmm... I'm fairly handy with the spool gun...

PE comment below

Originally Posted by darylat8750

I replaced a SS tank with "plastic". I had to cut the original 250 gallon tank into several pieces in order to get it out. It was an irritating, noisy job with a sawsall and I used up many blades. Some of the baffles were situated in such a way that several extra cuts on the outer walls were required to get an angle to cut the baffle.

I installed 2 plastic tanks in the same area with only a small reduction in total capacity.

Hmm... Beyond the expense, this is starting to be my favorite... I have lots of room to play with...

Originally Posted by UNCIVILIZED

The OP does. It's 2'x4'x5', thus 40cuft, & at 8gal/cuft, 320 gal.

leftbrainstuff,
In mentioning epoxy, I think that you're referring to something else. But when I mentioned epoxy, what I wss referring to, was completely encasing the tank in fiberglass & epoxy. It's an old technique, but likely still viable. And many a tank was built at the factory that way.
They've done it plenty with aluminum too.

Encapsulating sure would be a ton of work... but it WOULD work...

[minaret]

Originally Posted by HappyMdRSailor

This is from the inside out... water pooling in the tank, and electro-galvanic-hocus-pocus



Agreed... skinning the bottom is a terrible solution... I think I'll skip the individual tig filling... BUT... maybe a SS patch of the couple areas??? Likely to be only a few of about 4-6" square... Hmm... I'm fairly handy with the spool gun...

PE comment below



Hmm... Beyond the expense, this is starting to be my favorite... I have lots of room to play with...



Encapsulating sure would be a ton of work... but it WOULD work...

Regarding encapsulation, have you forgotten the method I showed you on my holding tank? This one could be a candidate. Sure isn't fun though!

[HappyMdRSailor]

Originally Posted by hellosailor

There are spray "wands" with nozzles designed to spray in a 360 pattern (sideways) all around them, used in automotive rustproofing, where they are inserted into a closed body cavity through one small hole. That should handle the thick material of a tank liner, or the companies that make the liner should be able to recommend something.


With that kind of pitting...I'd want to really go guerilla on any coating, to make Real Damn Sure it was 100% and more. And even then, I'd consider adding a bladder inside the tank, so there was even less chance of leakage.


Of course with all that time and money, it might be cheaper (and certainly more reliable) to consider cutting up the tank, if that's really necessary, and replacing it with perhaps two tanks, that could be installed without any further demolition.

I didn't even think about a 360 wand, let alone actually spraying... I have some access holes in each quadrant now... Done creatively, I bet I could reach every surface... easier with a brush, but possibly spray

Splitting the tank is starting to have merit... I'm going to need to do some measuring!!!

Originally Posted by Compass790

You could use stainless steel pickling paste on the corrosion first. That works good at killing the corrosion. No doubt the bottle tells you to wear gloves & respiratory protection. Any stainless welding place will have it if you only need a small amount. Have to wash off with water tho which will create another problem. Maybe flexible epoxy would be worth a shot if the aircraft tank sealant is too expensive for you.Let us know what you go with.

I'd do something for sure to take care of "NOT" trapping the corrosion... pickling, conversion, etc... Thanks for the pickle paste tip... I'm for sure going to update and post results... Funny.. I had a whole "proper way to make access ports" thread in mind from start to finish until I ran into this!

Originally Posted by petter5

As used in the maritime industry:

Belzona 1331 spray or brush applied coating

/Petter

Veeeeeery interesting!
Thanks petter!

[HappyMdRSailor]

Originally Posted by minaret

Regarding encapsulation, have you forgotten the method I showed you on my holding tank? This one could be a candidate. Sure isn't fun though!

I had INDEED forgotten !

My thoughts are like harbor seals, and my brain is the bell buoy

***licks fingers for thread search***

[minaret]

Belzona $$$$$$. Good product though.

[NSboatman]

Another vote for Belzona. 1831 surface tolerant version. Has saved many, many fuel tanks all over the world in industry and on boats.


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[captjcook]

When you are done playing around...a cutoff wheel will be a good choice to chop up tank. Two new aluminum tanks in 3/16 will be about two grand with senders....just a reference to work from for all the time you are spending. A desiccant dryer in the vent line and a polishing system will avoid most future problems...

Have fun!

Jim

Ps: Nice boat!


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[Rhapsody-NS27]

Originally Posted by captjcook

When you are done playing around...a cutoff wheel will be a good choice to chop up tank.

They do help get a tank out. Sometimes, the only way.

[sailcrazy]

We sail a 43' monohull, and our black iron fuel tanks showed very similar results during a cleaning and inspection a few years ago. Because of the installed baffles, access limitations, and unknowns we could not see....we elected to cut the tank up (angle grinder and cut-off wheel) and remove it. We had a new tank made out of 10mm close-linked polypropylene with welded seams and installed. Total project was under $1k, and has been trouble free since....no leaks, no corrosion, no issues. Definitely the right and easy choice for us. FWIW

[thinwater]

Originally Posted by HappyMdRSailor

This is from the inside out... water pooling in the tank, and electro-galvanic-hocus-pocus



Agreed... skinning the bottom is a terrible solution... I think I'll skip the individual tig filling... BUT... maybe a SS patch of the couple areas??? Likely to be only a few of about 4-6" square... Hmm... I'm fairly handy with the spool gun...

PE comment below



Hmm... Beyond the expense, this is starting to be my favorite... I have lots of room to play with...



Encapsulating sure would be a ton of work... but it WOULD work...

If you decide to weld internal patches--a perfectly acceptable code repair for floors--make CERTAIN the patches have well-rounded corners. In my old day job I was a tank inspector (up to 10 mm gallons) and I saw many cracks originate from square patches. It is also against code. Try for a 3" radius.

[HappyMdRSailor]

Originally Posted by captjcook

When you are done playing around...a cutoff wheel will be a good choice to chop up tank. Two new aluminum tanks in 3/16 will be about two grand with senders....just a reference to work from for all the time you are spending. A desiccant dryer in the vent line and a polishing system will avoid most future problems...

Have fun!

Jim

Ps: Nice boat!

Luckily for me I own multiple cutoff wheel spinners... from finesse to freight train... Big fan of the vent desiccators...
And ThankYa!

Originally Posted by Rhapsody-NS27

They do help get a tank out. Sometimes, the only way.

Indeed!!! Your dad woulda handed you a beer and said "well done son"

Originally Posted by sailcrazy

We sail a 43' monohull, and our black iron fuel tanks showed very similar results during a cleaning and inspection a few years ago. Because of the installed baffles, access limitations, and unknowns we could not see....we elected to cut the tank up (angle grinder and cut-off wheel) and remove it. We had a new tank made out of 10mm close-linked polypropylene with welded seams and installed. Total project was under $1k, and has been trouble free since....no leaks, no corrosion, no issues. Definitely the right and easy choice for us. FWIW

New manufacture is definitely still on the list...

Originally Posted by thinwater

If you decide to weld internal patches--a perfectly acceptable code repair for floors--make CERTAIN the patches have well-rounded corners. In my old day job I was a tank inspector (up to 10 mm gallons) and I saw many cracks originate from square patches. It is also against code. Try for a 3" radius.

Thanks TW... I would have rounded, but nowhere near 3"... likely near 1"... Great tip!

[HappyMdRSailor]

Going with the aircraft fuel cell sealer as proposed by a64pilot. ..

It's on the way here. .. will update!

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