Diesel tank sealant - Flowliner or alternatives?

webcraft

webcraft

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I've had the alloy diesel tank welded up and have painted it. A friend has advised using one of those slosh-about tank sealants, but I reckon it would be very expensive for this size of tank. Tank is about 75 litres, maybe a bit more. Flowliner is £40 for enough to do a 25l tank.

Any alternatives ?

- W
 
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By "alloy" you presumably mean of aluminium? It's difficult enough to get anything to stick to the stuff permanently and reliably, even if it's not had diesel and associated crud sloshing about in it for years. The consequence of even a few bits flaking off is not attractive...

P.S. Aluminium tanks are something of a rarity on this side of The Pond, but commonplace in the US. You may get some pointers on a forum more frequented by 'Muricans.
 
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webcraft said:
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Nobody used anything similar?
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Doubt it - partly for the reasons macd gives and partly because not sure it is a good idea.

You could of course seek advice from the manufacturers of such products as to their suitability in your application.
 
webcraft said:
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I've had the alloy diesel tank welded up and have painted it. A friend has advised using one of those slosh-about tank sealants, but I reckon it would be very expensive for this size of tank. Tank is about 75 litres, maybe a bit more. Flowliner is £40 for enough to do a 25l tank.

Any alternatives ?

- W
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I wouldnt use it, for all the reasons given and the fact that it is a bodge, a get you out of trouble temporarily bodge.
 
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Liquid tank liner/sealer is widely used in the vintage motorcycle business with - according to a friend of mine who has used it often - remarkably good results if used as per the instructions. There are many different brands.

It is not intended as a 'bodge', the tank has been cleaned out, the affected sections of seam have already been cut out of the tank and a new bit welded in, two coats of aluminium primer applied plus (so far) one topcoat of Rustoleum All Surface Paint. Using a liquid tank sealer is just a further precaution with the intention of increasing the odds of the tank lasting a few years - or at least until I can afford to have a custom tank made.

I was hoping to hear from someone who had done this, warblings of doom from people who have not done something are ten a penny in this place . . . thanks anyway though for the dire warnings.

- W
 
webcraft said:
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Liquid tank liner/sealer is widely used in the vintage motorcycle business with - according to a friend of mine who has used it often - remarkably good results if used as per the instructions. There are many different brands.
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...many of which have failed or will fail because they are not resistant to ethanol.

As suggested, why not try a US forum? Aluminium tanks are so rare over here that you'll get little by way of practical experience.
 
macd said:
...many of which have failed or will fail because they are not resistant to ethanol.

As suggested, why not try a US forum? Aluminium tanks are so rare over here that you'll get little by way of practical experience.
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All the tank sealants currently on sale are marketed as being resistant to ethanol.

- W
 
macd said:
UK fire doors are marketed as surviving a standard test for 30 minutes, but...

Instead of squabbling about irrelevancies, why not work on the constructive advice you were given?
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It was you who brought up ethanol resistance, so I am a bit mystified as to why you are now saying it is an irrelevance.

As far as I am aware the only constructive advice I have received here so far is to try a US forum. I have now put a post on Cruiser Forum and will report back if I get any sensible advice.

- W
 
I have read the Flowliner info on internet, as no doubt you have. Nowhere does it mention aluminium tanks. I would expect to etch prime this metal but you may struggle to find an etch paint system that is compatible with epoxy.

Can you lay up grp on the outside instead? Adhesion is then less critical.
 
webcraft said:
It was you who brought up ethanol resistance, so I am a bit mystified as to why you are now saying it is an irrelevance.

As far as I am aware the only constructive advice I have received here so far is to try a US forum. I have now put a post on Cruiser Forum and will report back if I get any sensible advice.

- W
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And it was you who brought up motorcycle petrol tanks.

"the only constructive advice" came from me. You're welcome.
 
vyv_cox said:
I have read the Flowliner info on internet, as no doubt you have. Nowhere does it mention aluminium tanks. I would expect to etch prime this metal but you may struggle to find an etch paint system that is compatible with epoxy.

Can you lay up grp on the outside instead? Adhesion is then less critical.
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GRP-ing the outside is an excellent idea - except that increasing the dimensions by as little as 1mm would render it impossible to get the tank back through the lazarette hatch :-(



- W
 
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Well, the consensus on Cruiser Forum seems to be that it is not the aluminium that is an issue, it is the diesel, more likely to leak past/through things than petrol. I might need the same sealer that they put in aircraft tanks - which sounds a bit expensive - so it is sounding like a non-starter at the moment.

The leaky seam has been cut out and the new metal is freshly painted, so fingers crossed all will be well - another coat of paint, new tank fittings then put it back in is the plan.

Thanks MacD for the US forum suggestion.

- W
 
If you have a search through my fairly recent posts, I sealed the inside of my tank with a product but I can't for the life of me remember what it was called.
Anyway, it's designed to be agitated inside a small tank, but after a chat with the manufacturers I used it by slapping it on with a brush and kept reapplying it to keep it well wetted in the solution.
Because it was used in that way, I needed far less than the recommended amount for my tank size. The manufacturer actually recommended I bought the smallest size tin they offered, but I got the next size up for my own piece of mind.
That was in January (I think) and I'm currently sitting just above the fuel tank on the boat in Holland where it's still firmly holding the diesel inside!
Feel free to pm if I can help further.
 
I used to own a Catalina that had an aluminium alloy fuel tank. Afyer 20 years it developed a few performations where it had been in contact with a wet bilge.

I sent it to a co. in Devon to be cleaned and repaired: they cleaned it and welded a patch over the perforations. Did a good job too.

And now the fuel tank is again leak free. Also, there is no traces of red diesel that could upset unspeakable foreign customs officials. White diesel and Marine 16 are the only things that have been put in the tank since. The repair/clean cost about GBP 120 if I remember correctly...
 
webcraft said:
[ . . . and the new metal is freshly painted, so fingers crossed all will be well - another coat of paint, new tank fittings then put it back in is the plan.
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I guess you're painting the outside? I wouldn't put anything in the inside as it only has to flake off a little (and aluminium is notorious for shedding coatings) and you will have blocked filters and fuel starvation for ever and a day.

The secret to long lived aluminium tanks is to make sure water and crud is regularly removed from the inside, and that the mountings on the outside are things like hard rubber or direct solid bolting, with plenty of room for air to circulate. Don't sit the tank on anything, or chock it with anything that can become 'damp' like wood, webbing, foam, etc. Replacement aluminum tanks was a steady earner for us at the yard as most US power boats had their tanks 'foamed' in place.
 
Motor_Sailor said:
I guess you're painting the outside? I wouldn't put anything in the inside as it only has to flake off a little (and aluminium is notorious for shedding coatings) and you will have blocked filters and fuel starvation for ever and a day.

The secret to long lived aluminium tanks is to make sure water and crud is regularly removed from the inside, and that the mountings on the outside are things like hard rubber or direct solid bolting, with plenty of room for air to circulate. Don't sit the tank on anything, or chock it with anything that can become 'damp' like wood, webbing, foam, etc. Replacement aluminum tanks was a steady earner for us at the yard as most US power boats had their tanks 'foamed' in place.
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The rot was all at the bottom corner where the fuel take-off and drain are. It was already a new piece welded in. That is now replaced again, and the whole tank thoroughly painted. I don't think there were problems anywhere else. The boat has sat on the hard for many years with little use, so any water would accumulate in that corner. As the whole piece has been replaced with new metal it should be OK as long as water is not allowed to accumulate and sit there again.

Tank is bolted onto glassed in bolts with four flanges, so the bulk of it is not in contact with anything.

If I put the tank back in then leave the boat on the hard for six months should I leave the tank empty or with a small amount of diesel in to fill that corner?

- W
 
webcraft said:
. . . If I put the tank back in then leave the boat on the hard for six months should I leave the tank empty or with a small amount of diesel in to fill that corner?
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You're best off leaving it brim full of filtered diesel. Or at least diesel mixed with your favourite 'conditioner' and that you have left to settle in the tank and then have drained any settled water from it.

Empty and part full tanks can have condensation issues allowing water to gather at the low point.
 
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