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-   -   Should I fear steel tanks? (https://www.trawlerforum.com/forums/s18/should-i-fear-steel-tanks-57348.html)

cardude01 04-18-2021 08:50 PM

I have one aluminum tank on my boat. Centerline and not down in the bilge. Do I have to worry about aluminum as much as I would with steel? I didnít think I did.

DDW 04-18-2021 11:06 PM

I had an aluminum tank on a sailboat fail, corroded from the outside in. It was sitting on the hull and the lowest corner of the recess could trap water and was not iimbered. It lasted about 20 years that way. I cut the lower corner off and patched it, limbered the recess, and reinstalled it sitting on DriDeck. That way I could rinse around it to remove any accumulated salt and it would dry.

sunchaser 04-19-2021 05:17 AM

Quote:

Originally Posted by sean9c (Post 997288)
Glad that I've fiberglass tanks, I don't even think about them. Made a pair of fiberglass tanks for a friend with a TT that had rotten metal tanks. Not all that much work or expense, wouldn't even consider replacing metal tanks with metal.

Sean, did you find that some FRP products are better rated for diesel than others? When alcohol started being added to gasoline some FRP tank material proved unsuitable.

captobie 04-23-2021 01:12 PM

My previous boat had 50 year old steel tanks, no issues at all with them.

GT6 04-23-2021 01:14 PM

Tanks
 
I have no idea whether or not you can replace the fuel tanks without doing surgery on the decks, etc. In our case, when an aluminum tank failed we had to slice open the deck to R&R tanks.



But as a tank manufacturer, I do have a few thoughts/opinions on tank construction and design...


1. Virtually all marine tanks should be top fill and top draw. If a tank has a bottom outflow, it's another potential failure / leakage point.



2. By nature, you are operating in a damp, salty air environment. Steel is prone to corrosion with or without direct contact with water.



3. Attempting to internally coat the interior of a baffled tank rarely works well. Just too many nooks & crannies to ensure good, 100% coverage of coating. We discontinued that practice several years ago.


Ed

Andiamo2018 04-23-2021 01:20 PM

Tanks less than full get water inside
 
There is water in air. Condensation will happen inside of any tank as it does on the outside of a glass of ice water. The less full the tanks the more air and thus the more condensation. If a boat sits for years without moving it will accumulate water in the fuel tank.

Bob M 04-23-2021 01:41 PM

For metal to rust, two things are required: water and air.

If the tanks are dry on the outside, they won't rust from the outside. If they're water free on the inside, then they won't rust from the inside.


Outside water is more likely to corrode than inside water, since there isn't much air inside a tank, particularly if the boat is stored with full tanks.


It's unusual for a motor vehicle to not have steel tanks and these tanks are exposed to water every time it rains. In 60 years of driving, how often have I had to replace a fuel tank because it corroded? Never.


That said, if the bottom of a steel tank is in bilge water, I wouldn't buy the boat.

Xlantic 04-23-2021 02:01 PM

Quote:

Originally Posted by cardude01 (Post 997293)
I have one aluminum tank on my boat. Centerline and not down in the bilge. Do I have to worry about aluminum as much as I would with steel? I didn’t think I did.

My almost 50 years old “black iron” (carbon steel) fuel tanks don’t leak and have no sign of rust.

The aluminum fuel tanks in my 20 year old Avon Seasport Jet tender did develope a small leak which I repaired with epoxy.

I think it depends on the tank getting wet or not.

Begorrah 04-23-2021 02:02 PM

Petroclean up above Seattle epoxied the inside of my steel tanks. They pumped the diesel out, saved it then cleaned it and put it
back in after they fixed the tanks. They cut 3 port hole in each tank, cleaned the tanks and then epoxied the inside about 4" up from the bottom. Better cost than pulling the engines to get the tanks out and replace them.

GT6 04-23-2021 02:02 PM

Quote:

Originally Posted by Bob M (Post 998952)
For metal to rust, two things are required: water and air.

If the tanks are dry on the outside, they won't rust from the outside. If they're water free on the inside, then they won't rust from the inside.


Outside water is more likely to corrode than inside water, since there isn't much air inside a tank, particularly if the boat is stored with full tanks.


It's unusual for a motor vehicle to not have steel tanks and these tanks are exposed to water every time it rains. In 60 years of driving, how often have I had to replace a fuel tank because it corroded? Never.


That said, if the bottom of a steel tank is in bilge water, I wouldn't buy the boat.




Bob, not really correct...



Marine fuel tanks live in a damp, salty environment. If you keep them "dry", which means zero humidity, they will last a long time for sure. I know of no boats that have a zero humidity environment in the engine room.



All tanks create water inside, as the previous poster explained. There is moisture in the air than condenses inside the tanks. That is why good boat owners run water filtration cartridges. Racor, Facet, Velcon, etc...


It has been common practice for cars & light trucks to have plastic fuel tanks for several decades now. Your gas powered car or truck easily accepts typical amounts of water in the fuel, and your plastic gas tank doesn't rust out. You have water in your car's plastic gas tank right now.


Diesel powered vehicles always have good water separator filtration. My Chevy pickup has a water in fuel sensor in case the filter cannot contain any more water.



My 68 year old Jaguar has a steel tank, which has always had minor rusting inside. At least for the 40 years I've owned it... At one point I had to have it resealed and coated internally to keep the fuel from leaking, and the rust from clogging the fuel filter.

Nick F 04-23-2021 02:09 PM

I see a number of people preferring top-draw fuel take-offs on the premise that this reduces the risk of fuel spillage from a leak in the fuel piping between tank and engine. Bear in mind that, if the leak in the fuel piping is below the fuel surface level in the tank, the fuel will also spill from a top-draw due to siphoning. The top-draw is not giving you the protection you think (unless your tanks are below your engine).

As you might have guessed, I am in favour of bottom-draw in large bore piping to get the crud and water out of the tank and into the primary filter/separators.

Nick

dutch-barge 04-23-2021 02:31 PM

well our boat has steel tanks fitted in 1930 and they are still good..

Tator 04-23-2021 03:05 PM

Our top feed/fill steel tanks are 43 years old with no problems or signs of rust. In 16 years and thousands of engine hours of use, I've never had water in my Racor. I dip the tanks every couple of years with a dowel and water detecting putty and it has never shown an indication of water in the bottom of the tank nor any crud. The tanks are mounted on fore and aft fiberglass rails. Because the salon is full width, there is not many ways for water to leak on them from above.

Tator

CarlF 04-23-2021 03:44 PM

Is there any recent survey of the boat? If not, I wouldn’t go any farther in negotiations without a surveyor looking at the tanks. Won’t cost much if you tell the surveyor to only look at the tanks for now.

Sieben 04-23-2021 03:44 PM

Quote:

Originally Posted by Comoshun3 (Post 996876)
Hi all
I am new to the forum and Sadly, between trawlers.
In an effort to rectify this situation I am negotiating on a 1998 N46. As it turns out, this boat has steel tanks (pre Hull 68) and I am wondering how concerned I should be.
In an effort to be proactive can anyone offer any information on dealing with corroded tanks on this model?
Can they be removed through the salon floor and cockpit door (after removing the engine of course)?
Are there any reliable methods of repairing/treating the tanks in place?
What would a ball park figure be to replace the tanks on this boat?

Thanks in advance.

Hi there. We currently own a 1985 Passport 42 sailboat. Built in Taiwan. Tanks are fiber glassed over the steel. The usual issues regarding rust or sediment are condensation getting into the tanks. Or deck leaks from the fill following down to the top of the tank and rotting the fitting. Our boat has not had an issue. Some both power and sail of this era have.

Keep them "pressed" full with fuel especially in the winter. Fuel oil prevents rust. Drain off the bottoms. We have bottom drains and top fuel pickup. Some owners in our group have had a pin hole rusted at the weld seams. Some members of our group used an aircraft sealant made for tanks to seal all the seams and to coat the interior of fuel tanks in airplanes. This was done to a few leaking tanks which were on 1980' boats made of mild steel. Worked successfully with no loss of volume.

From a forum member from our group:

"They had some pitting too in the bottom of the tank where water had sat and a fairly large hole in one of the corners. So I first had used JB weld to patch the known hole in the corner where I could stick a screwdriver through. I was worried about longevity because the tank is the one in the keel with both sides glassed to the hull so likely to flex and work some.

I used two different 3M products, I'm not sure exactly which ones they were. I think the letter is for viscosity with A being the thinner and B being thicker.

The first was thick like a caulk which i used to seal all the seams like this:
https://www.skygeek.com/3m-aerospace...k-sealant.html

The second was a bit thinner, brushable, but self levelling which I used to coat the insides.
https://www.skygeek.com/3m-aerospace...-2-oz-kit.html

Also, I could only get to one side of the tank because of the baffle, so I had to cut a hole in the top and add an inspection plate to the other side.

I still want to do my other tanks at some point as a preemptive solution."

Hope this helps one with a leaky steel tank.

John

High Wire 04-23-2021 04:47 PM

My experience from my 1986 Phoenix 29 was outright scary. In 2000 my two 80 gallon aluminum main tanks were corroded badly. The ground connection tabs completely disintegrated. The outside surface was covered in powdery aluminum oxide. I also had two saddle tanks that looked new and a center line tank that looked new but completely obstructed access to vital things like shaft packings, seacocks and such. I decided to replace the mains and all of the fuel hoses. The saddle tanks needed to come out first before the mains. Long story short the perfect looking saddle tanks had holes in the bottom that a pencil would fit though under the glued on neoprene strips installed by Phoenix when constructed. The aluminum transformed into a gray tooth paste looking substance on the bottoms of all of the tanks. All five tanks contained gasoline prior to the replacement job and never indicated any leakage. The thoughts of water and sludge common in an aluminum diesel fuel tank is a no-go for me. Good luck.
______________

MVDarlin 04-23-2021 06:56 PM

I had my black iron 300gal (2) tanks cleaned and inspects in my 1982 Ocean Alexander 2 years ago. A hole was cut for access. 5 gal of bio goo gunk was removed from each tank. Other than that they tanks were fine. Keep them full, otherwise condensation will cause water to collect in the tank.

Soo-Valley 04-23-2021 07:53 PM

It seems as if tanks may fail sooner on lack of use. If the water is left in the tank as opposed to separated in the filter. So low overall engine hours on the life of the boat causes tank failure. Never mind, Just pondering a thought here.

mickand 04-23-2021 08:06 PM

I have 40 year old steel tanks with no top rot.
Last year I took off one of the large inspection ports on one tank and went in with an endoscope to find a surprisingly clean tank with no obvious issues.
I've been using Diesel-Shok in my fuel for the last six years and it seems to be paying off.
Diesel-Shok is sourced from USA Fuel Service and it holds any water in suspension within the fuel.

rolomart3 04-23-2021 11:19 PM

Perhaps it is possible to use a bladder diesel tank from IPI as a liner inside the corroded steel tanks. These bladder diesel thanks can be custom made to fit and are military grade. Then, there is no need to replace or break anything in the boat. The only thing needed is an opening in the current metal tanks to insert the bladders.
Such an arrangement would make possible to remove the bladders to clean outside the boat or even replacement.
It would really take out all fear of steel tanks. More important, it would reduce a bit the fear of most marine pleasure boat manufacturers.


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