Powder coating or bare aluminum for custom gas tank build?

[imonna 19 6]

Hello all,

Hearing two different opinions for fabricators an a new gas tank for my 19' 6".   One says powder coating good the other saying Powder Coatingh bad.  

Anyone have first hand experience on this issue.


The PC problem posed by the PC BAD opinion is that a chip on the coating will be an entry point for water which could then seep between the powder coating and aluminum and cause corrosion,. whereas a bare aluminum tank would not have this problem.

Thanks in advance

Bill

[flounderpounder225]

Bill
Coal Tar epoxy, High solids 2 part epoxy, this is what I have heard is the best for coating fuel cells when replacing.  No personal experience, just word of mouth from around the docks....
http://www.jamestowndistributors.com/1/ ... rimer.html

Marc

[Capt. Bob]

The idea of painting/coating is to keep the tank from corroding.
I'll assume you feel the cause of corrosion is, for the most part, water. Both salt and fresh.

That stated, then I'd be correct in saying that anything one does to keep the tank surface as dry as possible, since the tank resides in a vessel that itself functions in water, helps limit corrosion.

Therefore, keeping the tank dry extends its useful operating life.

Do this. Clean sections of the tank where there was no mounting material to trap water. How much better would that area look if it had been painted.
No much I'd bet. Aluminum resist corrosion quite well on its own.

Conclusion.
Keeping the tank dry is what keeps it from corroding. Mount it so water can't be trapped between the mounting and the tank surface. Secure the coffin to keep as much water from entering as possible. If you can possibly find some way to circulate air around the tank to help remove moisture, do it. Paint/powder coat/two part epoxy whatever floats your boat but in the end, keeping water from being trapped against the surface is the key.

Good luck.

[slvrlng]

Why is the one guy suggesting powder coating?
Read this thread from bateau2.com. I like the way he has completely sealed the tanks in after coating and mounting. They are tilted towards the back of the boat with some drain holes cut in the back edge of the bulkheads so if any trash gets in there he can open the access and wash the tops off. I really like this way of mounting the tanks because there is no way any moisture can get to them.

 http://forums.bateau2.com/viewtopic.php ... 7&start=70

[wingtime]

Powder coating will protect the outside of the tank but what about the inside?  Also any chips in it will be a problem.  Todays corrosive ethanol gas is a bigger threat than anything to your tank.  I think coating it is a waste of money.  How long do you expect to keep the boat?  The tank in my boat was 30 years old when I replaced it and it wasn't even leaking.  Clearly poor care of the boat and the sealant around the coffin cover allowed water into the coffin.  That is what caused the corrosion pits I found under the foam tape someone put under the straps.   It is TRAPPED water against the thank that is the problem.  It's ok if the tank gets wet now and then it just has to be able to dry out after it gets wet.  After all they are built with a marine grade aluminum alloy.

[gran398]

Agree wingtime. The pitting on the six year old tank out of Miss Marco occurred exactly where CB suspected, on the bottom where water was trapped between the neoprene and the aluminum strap. In-proper install.

Bought two new 207 gallon ea. aluminum tanks three years ago for a 34 Hatt. They came from the factory epoxy coated. But I'm with a lot of you, the new tank to be installed on Miss Delmarva will not be painted, coated, or powder coated. Just carefully installed with MUCH attention paid to water entrapment, drainage, airflow, etc.

Those interested may know of Bayside Marine, the pics posted a few days back were of their work. I'll be ordering some items from them. Have had interesting conversations with the owner. He says they take a 2" piece of PVC, split it to make a fore to aft trough at the lowest point in the tank coffin (the "bilge" if you will.) Then they foam the tank in. THEN they lay fiberglass cloth from the outside of the stringer, onto the 2 inches of outer foam, and then onto the roughed-up tank for about two more inches. He says it keeps any moisture from seeping into the foam.

My rebuild guy says this is not necessary. But WTHay, may as well report it all for sake of information/discussion.

Best on your install!

[imonna 19 6]

The powder coating comes on the tank if built by the company out of New Jersey- Speedytanks.  Their logic is that it keeps water off tank.

 Local fabricator is the one that disagrees for reasons stated above.  I will be sparing no expense or effort to install properly and have done much research on this and other sites on install methods.


 Now its about figuring out what is the best tank to buy.

[gran398]

Wanted to powder coat my new tank initially as well. Asked the boys here about it a while back. After discussion, the idea of seepage and subsequent festering beneath the coating led me in another direction.

Have seen aluminum corrosion beneath a painted surface. It spreads. And the bottom line is, powder coating, although far superior, is still paint.  

I'll install mine in her birthday suit.

[gran398]

PS...keep us posted as to your decision.

Tx!

[seabob4]

The key to applying tank rubber to the bottom of the tank is to apply lengthwise, not crosswise.  You never want to have water, be it fresh or salt, laying against the tank for any length of time, allowed to do it's dirty work, as CB alluded to.

Again, as CB alluded to, the REAL key is to keep the tank compartment dry.  Don't powdercoat, don't coal-tar epoxy.  Just provide a good platform for the tank to sit on, provide good drainage from the forward compartments underneath the platform, and seal the tank hatch and access pies so that water can't intrude from above...

[imonna 19 6]

The key to applying tank rubber to the bottom of the tank is to apply lengthwise, not crosswise.  You never want to have water, be it fresh or salt, laying against the tank for any length of time, allowed to do it's dirty work, as CB alluded to.

Again, as CB alluded to, the REAL key is to keep the tank compartment dry.  Don't powdercoat, don't coal-tar epoxy.  Just provide a good platform for the tank to sit on, provide good drainage from the forward compartments underneath the platform, and seal the tank hatch and access pies so that water can't intrude from above...

Exactly my plan.

After the above comments I am thinking I will stick with straight aluminum.   My coffin is solid with a stern side drain to the bilge (which also rarely has water in it).  I will be installing the tank per

http://marinesurvey.com/yacht/fueltank.htm

I plan on sticking to this method, except i will be securing the strips to the tank alone the length so water runs easier bow to stern.  After its in io i will re-caulking the coffin lid seams, under all access hatch's and screw holes.

[Capt. Bob]

My last thoughts.

Painting/coating the tank is a lot like faith. If it helps ease your mind, then by all means do it.
I have no personal experience whatsoever that a chip in the coating will allow water to leach underneath and lead to corrosion. I do know (from my own experiences with two different tanks and mounts plus a boat load of members photos) that water trapped by foam tape under mounting straps and (in one case, rubber supports) will cause a tank to fail before its time. These devices are porous and large (relative to a couple of mils of coating) and will hold the water. I just don't see that happening with a paint chip any more than on the bare surface. To me, it's hedging your bet.

That stated, the dry coffin is the key but I'll also add, proper securing of the tank is just as important. If it tends to "slip 'n slide", then that too hastens failure by abrading those areas that may have minimal corrosion. OEM tanks that show the first signs of a leak often do so when they have been loaded to near capacity and the craft used in choppy conditions. This can even include a long tow to a distant fishing site (on the trailer).

Good luck.

[gran398]

Just ordered the new tank from Alloy Marine. Phil the owner was very nice, easy to deal with. New capacity, 80 gallons.

Asked him specifically about powder coating. They do it upon request. He says it is not necessary. He said if you wanted to do something additional, spray it with zinc chromate primer. But he said that was not necessary either.

[gw204]

I think the same can also be said about the wood/no wood argument.  Is one particularly better than the other?  Not really as long as you use appropriate build practices.

One this is for certain though (at least in my mind), mention a coated tank and no-wood contruction when you go to sell the boat, and you won't have as many people telling you that you did it wrong...and your resale will be higher.

My Mako and Formula are both getting epoxy coated aluminum tanks, wood cores and vinylester resin because that's what I'm comfortable with and that's what the budget allows.

[Capt Matt]

I had my custom fuel tank for my flatback made at action welding in Cape Coral FL.  Bruce was very helpful and I ended up with a great product. After alot of research and conversations with the tank builder I did not coat it with anything. I made short stringers that run the length of the tank to support it in the coffin. They hold it about 4 inches off the bottom of the hull. Both the forward and aft bulkheads have drains that run into to the bilge. Before installing it I marked the bottom of the tank the same width as my stringers with a marker and roughed it up as the tank came spayed down with corrosion X . Then I used 5200 to stick hard plastic strips the length of the tank. Making sure not to get any voids between the tank and the strips  I placed bricks on the strips till the 5200 went off. I searched all over for a hard plastic strip but ended up using two seals for the bottom of garage doors I found at Lowes. I cut the thin plastic off which left me a 8ft piece of 1/4 hard plastic. I also 5200 ed the strips the length of the top of my short stringers. I had 3 brackets on each side of the tank welded on that I bolted through the stringers with stainless bolts and washers using coosa board scraps as spacers. filling the bolt holes with 5200 also. This should give it plenty of room to breath and no way water can get trapped against the tank
Capt Matt