Coating for SS fuel tank pitting...

[Cheechako]

The proper cleaning solvent for aircraft fuel sealant work (at least for Boeing stuff) is MEK.
The OP said he couldn't get the tank out; Having a new bottom put on will lead to future pitting anyway with SS. it can happen surprisingly fast. The bottom was all the way thru on a boat I had 7 years after the boat was new.
But if he could get the tank out, go with a plastic tank for sure!

[bsurvey]

while the tank should be replaced with aluminum as stainless steel is not compatible with diesel due to sulfur embrittlement.


you may use belzona. they use it in nuclear power plants on there cooling pipes. also JB weld

[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.

[leftbrainstuff]

Originally Posted by HappyMdRSailor

UGH!

Revisiting my long overdue fuel tank scrub and access plate manufacture/install.... Upon initial cleaning I've discovered the dreaded "pits"!

It's only on the bottom of the tank, and probably in the neighborhood of 5% overall... Unfortunately, the pictures revealed deeper pitting than I thought, so doing nothing seems stupid...

I've successfully coated tanks before, but herein lies the problem... This sucker is big, and can't be removed, rotated, i.e. impossible to fully coat... I'd love to be able to simply coat the bottom... BUT... I'm concerned that a coating edge inside a diesel tank is begging for coating failure... To compound the problem, I'll bet there's some pretty good flexing in the tank bottom...

After a few thread research moments, I came upon two recommended products by minaret, but contacting the first they say "must be fully coated"
Product 1
https://www.kbs-coatings.com/tank-sealers.html

Product 2
I haven't called yet...
POR-15 Fuel Tank Repair Kit


Of course I could just pour in 20 gallons of epoxy and call it a day !

Any thoughts my brethren???

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.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[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.

[UNCIVILIZED]

Originally Posted by a64pilot

Wait a minute, who has a 320 gl tank?

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.

[lateral]

Originally Posted by UNCIVILIZED;2080245
[B

leftbrainstuff[/B],
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.

Did that with mine. Used high elongations epoxy dbh30 and DB.
Wasn't that bad & now the boat doesn't smell of diesel.

[a64pilot]

Originally Posted by UNCIVILIZED

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

Geez, I never thought a 48' sailboat would have that big a tank, but didn't think it would have 110 HP either, I didn't have a clue it seems.

[Scaramanga F25]

Fuel tank sealer may be toxic or at least leave a taste it the water, no?

[a64pilot]

Fuel tank, I certainly wouldn't put fuel tank sealer in a drinking water tank


Sent from my iPad Pro using Cruisers Sailing Forum

[geoleo]

Originally Posted by HappyMdRSailor

UGH!

Revisiting my long overdue fuel tank scrub and access plate manufacture/install.... Upon initial cleaning I've discovered the dreaded "pits"!

It's only on the bottom of the tank, and probably in the neighborhood of 5% overall... Unfortunately, the pictures revealed deeper pitting than I thought, so doing nothing seems stupid...

I've successfully coated tanks before, but herein lies the problem... This sucker is big, and can't be removed, rotated, i.e. impossible to fully coat... I'd love to be able to simply coat the bottom... BUT... I'm concerned that a coating edge inside a diesel tank is begging for coating failure... To compound the problem, I'll bet there's some pretty good flexing in the tank bottom...

After a few thread research moments, I came upon two recommended products by minaret, but contacting the first they say "must be fully coated"
Product 1
https://www.kbs-coatings.com/tank-sealers.html

Product 2
I haven't called yet...
POR-15 Fuel Tank Repair Kit


Of course I could just pour in 20 gallons of epoxy and call it a day !

Any thoughts my brethren???

20 gallon epoxy

[Rustic Charm]

Ive got an odd shaped keel tank of 200ltrs. But luckly mine is steel rather than thinner stainless and its built into the keel it self. Two years ago i contemplated sealing it with sealer products. In fact, i suspect the bottom has been sealed with pour in epoxy.

Whilst researching pour in's i was recommended a spray in nozzel that was attached to various lengh polls and then the spray comes out in a spray pattern like a dandylion shape. I was advised to spray 2 to 3 times after each coat had dried. The cost seemed prohibitive considering it was only pitting and rust i was worried about.

Then i come across the Fuel Right product and i thought id give it a year to see if it helps. It did. Massive rust reduction. Though ive read that others believe the product increases pitting, i doubt thats what's happening. Ultimately i believe if my problems do increase to leaking, then my solution will be an expensive partial keel replacement. But for your minor problem, Fuel Right may be a very cheap solution.

[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.

[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.

[leftbrainstuff]

Originally Posted by bsurvey

while the tank should be replaced with aluminum as stainless steel is not compatible with diesel due to sulfur embrittlement.


you may use belzona. they use it in nuclear power plants on there cooling pipes. also JB weld

Rubbish.

This is not an elevated temperature application for stainless steel. Embrittlement is not an ambient temperature phenomenom.

If you are going to make material compatibility statements please support it with an appropriate reference.

Stainless steel, specifically low carbon 31X grades are ABYC approved for use as diesel fuel tanks.

http://www.passagemaker.com/articles...l-tank-design/

The issues with stainless diesel tanks relate to the potential for crevice corrosion from water out of suspension.

https://law.resource.org/pub/us/cfr/....H-33.1989.pdf

Sent from my SM-N900T using Cruisers Sailing Forum mobile app