Steel Pontoon Rust....

bubba

Well-Known Member
8 psi is VERY HIGH for sealed toons. 3 psi is much better. Some of the newer toon boats ( tri-toons ) have gone away with pressure tanks and have added more bulkheads with looped coiled breather tubes. The loop is an air trap and allows venting and prevents water entry or sinking. Without increasing bulkheads you need that pressure for strength. With more bulkheads static pressure works fine.

All the fancy gas compounds to displace the air is a waste of money at this point in time - after you got ash you will never get you log back. Replace with AL toons if you must keep the boat.
 

Dave I.

Well-Known Member
8 psi is VERY HIGH for sealed toons. 3 psi is much better. Some of the newer toon boats ( tri-toons ) have gone away with pressure tanks and have added more bulkheads with looped coiled breather tubes. The loop is an air trap and allows venting and prevents water entry or sinking. Without increasing bulkheads you need that pressure for strength. With more bulkheads static pressure works fine.

All the fancy gas compounds to displace the air is a waste of money at this point in time - after you got ash you will never get you log back. Replace with AL toons if you must keep the boat.
You are right, 8 psi is Very high for these old pontoons. They might hold that much for testing but I wouldn't trust it for every day use. But, we are talking older toons so adding more bulkheads would be even less cost effective than probably replacing the entire pontoon. And you're right, you will never get your toon back after the rust starts, but without trapped O2, rust can't spread or develop any farther. That is the premise on how this topic started. Not restoring the pontoon steel.

I'm not sure what you mean by fancy gas compounds. That has me confused. But I did work in enclosed spaces for 15 years and gasses come second nature to me though because they were a life/death thing for my past work. Nitrogen is the most abundant gas in the atmosphere and actually relatively cheap. I just inquired about the price of it and if I was to order in bulk, a 300 cubic feet bottle would cost about $50. To almost completely displace the oxygen in 2 pontoons, it would cost $300 - $400 in Nitrogen. That is cheaper than I originally though.

Like it has been said, it really depends on the condition of you toons. If you look at the pictures I posted originally, they are pristine for being 43 year old pontoons and could be justified for the nitrogen treatment to stop/reduce the rust. BUT, you then look at Rivergoer's original pictures and you are right, it is past the point of going with nitrogen to prevent the rust. But, then after spending al that time and money doing those repairs, wouldn't it be worth a try to prevent rust again?

So, say I did get a request to try this and I could do it for $1500. That is a lot cheaper than a $15000 (steel) or $25,000 (aluminum) toon replacement. But there are just too many variables to justify trying it unless, like Rivergoer, you know for certain what the inside of your toons look like.

Even if I am never called to try this, Maybe someone will try it on their own. There is enough info here to put it all together and make it work. Would love to hear the results if anyone does try it.
 
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Powelldreamer

Well-Known Member
I have often thought about what could be done in steel pontoons. I work in the corrosion field for water, oil and gas. I have looked at water activated urethanes as a possibility. They react with water to create a dense foam either open cell or closed cell. The biggest single issue is removing the air or water from the steel surface This is typically accomplished by a tightly adhered coating. The coal tar that we use on the out side of the pontoons was a great coating back in the day but lacks certain characteristics for use on the water. Chief among them is UV resistance. While they offer excellent abrasion resistance they do not stand up to the sun. The other limiting factor is their poor flexibility. The pontoons are subject to different pressures bot external and internal that will cause the steel to flex. This will crack the coating.Lastly, who is checking to verify that the proper preparation is being followed? In order to attain a durable coating the preparation must be in accordance with certain standards. In addition the proper coating thickness must be achieved.

Urethanes will offer UV resistance and excellent abrasion resistance. They are however limited by their adhesion values. The ideal system would be to use an epoxy primer and then a urethane topcoat. This will give the adhesion we want from the epoxy and the urethane would provide the epoxy with UV resistance.

An epoxy/urethane system should last longer than what we all currently do so long as the correct preparations and procedures are followed.

Just my $0.02
 

Dave I.

Well-Known Member
I have often thought about what could be done in steel pontoons. I work in the corrosion field for water, oil and gas. I have looked at water activated urethanes as a possibility. They react with water to create a dense foam either open cell or closed cell. The biggest single issue is removing the air or water from the steel surface This is typically accomplished by a tightly adhered coating. The coal tar that we use on the out side of the pontoons was a great coating back in the day but lacks certain characteristics for use on the water. Chief among them is UV resistance. While they offer excellent abrasion resistance they do not stand up to the sun. The other limiting factor is their poor flexibility. The pontoons are subject to different pressures bot external and internal that will cause the steel to flex. This will crack the coating.Lastly, who is checking to verify that the proper preparation is being followed? In order to attain a durable coating the preparation must be in accordance with certain standards. In addition the proper coating thickness must be achieved.

Urethanes will offer UV resistance and excellent abrasion resistance. They are however limited by their adhesion values. The ideal system would be to use an epoxy primer and then a urethane topcoat. This will give the adhesion we want from the epoxy and the urethane would provide the epoxy with UV resistance.

An epoxy/urethane system should last longer than what we all currently do so long as the correct preparations and procedures are followed.

Just my $0.02
This would take us back to the Line-X product and conversation earlier in the thread. If you put a hard outer shell over the steel, with rust happening from the inside, you might be setting your toons up for ultimate failure while having a false sense of security that everything is fine. At least until it's too late.
 

Powelldreamer

Well-Known Member
This would take us back to the Line-X product and conversation earlier in the thread. If you put a hard outer shell over the steel, with rust happening from the inside, you might be setting your toons up for ultimate failure while having a false sense of security that everything is fine. At least until it's too late.
The line x is not the type of urethane you want to use. There are different urethanes that are much more elastic. Some can bridge a substrate crack that develops up to 1/4" in width and still maintain containment. Do not judge a material on the basis of a bad experience. There are many formulations that can work.
 

Dave I.

Well-Known Member
The line x is not the type of urethane you want to use. There are different urethanes that are much more elastic. Some can bridge a substrate crack that develops up to 1/4" in width and still maintain containment. Do not judge a material on the basis of a bad experience. There are many formulations that can work.
Not judging any materials at all, just stating a problem I foresee with anything that provides a barrier that does not allow small fractures, or small holes from within to expose themselves. Like I said, Line-x puts out an awesome product, but coating a pontoon may not be the best application.

What about closed-cell foam inside the pontoons? Wouldn't that dramatically reduce the amount of oxygen? Just thinking out loud. Forgive my ignorance. :)
Then the question of added weight comes in. How much does a closed cell foam weigh per cubic foot, them multiply that by 600. I do know my Playcraft is foam filled and I wish it wasn't just because of the weight factor.
 

Rivergoer

Well-Known Member
I considered the foam option. There was a mobile guy out of Texas that did steel pontoons. From what I read the downside was moisture would get trapped between the foam and steel accelerating the corrosion process.

Eventually the hull would rust away leaving the foam exposed to the elements. The foam would then quickly deteriorate due to UV exposure.
 

Dworwood

Well-Known Member
I have seen urethane foams actually accelerate corrosion on water piping. Never figured out if it was a chemical reaction or if moisture was trapped between the two. But those steel waterlines that were sprayed with foam for insulation underground didn’t last, at most 7 years and some only about three years. We always wondered if it was chemical and not moisture. Just something to consider but it destroyed those lines.
 

Powelldreamer

Well-Known Member
Not judging any materials at all, just stating a problem I foresee with anything that provides a barrier that does not allow small fractures, or small holes from within to expose themselves. Like I said, Line-x puts out an awesome product, but coating a pontoon may not be the best application.


Then the question of added weight comes in. How much does a closed cell foam weigh per cubic foot, them multiply that by 600. I do know my Playcraft is foam filled and I wish it wasn't just because of the weight factor.
Coatings work in three ways, barrier coatings, resistance inhibition and sacrificial.
Barrier coatings attempt to impede oxygen, water and soluble salts from the surface of the substrate.
Inhibitive coatings are typically barrier coatings with additives that hinder reactions from occurring at the substrate.
Sacrificial coatings are meant to act as the anode to the more cathodic substrate.

Ideally on steel pontoons you would use a zinc primer followed by a urethane topcoat.
The zinc primer would allow for defects in the coating but still protect the substrate because it has a more anodic material than the steel toons. This takes care of the imperfections of the coatings. It would then be top coated with the urethane coating to provide elasticity and UV resistance. This takes care of the external areas of the toon. The interior sections, in my opinion, should be galvanized or at a minimum have a zinc primer on them. This does not eliminate but would greatly reduce the corrosion issue that occur. In addition to all of these coatings, Anodes must be attached and maintained to prolong the service life of the pontoons. Proper anodes attached and most importantly not coated will go along way to preventing corrosion(rust) on steel pontoons.
 

Dave I.

Well-Known Member
Coatings work in three ways, barrier coatings, resistance inhibition and sacrificial.
Barrier coatings attempt to impede oxygen, water and soluble salts from the surface of the substrate.
Inhibitive coatings are typically barrier coatings with additives that hinder reactions from occurring at the substrate.
Sacrificial coatings are meant to act as the anode to the more cathodic substrate.

Ideally on steel pontoons you would use a zinc primer followed by a urethane topcoat.
The zinc primer would allow for defects in the coating but still protect the substrate because it has a more anodic material than the steel toons. This takes care of the imperfections of the coatings. It would then be top coated with the urethane coating to provide elasticity and UV resistance. This takes care of the external areas of the toon. The interior sections, in my opinion, should be galvanized or at a minimum have a zinc primer on them. This does not eliminate but would greatly reduce the corrosion issue that occur. In addition to all of these coatings, Anodes must be attached and maintained to prolong the service life of the pontoons. Proper anodes attached and most importantly not coated will go along way to preventing corrosion(rust) on steel pontoons.
But, since the inside of the pontoons are not protected and are, very possibly coated with rust, they can not be galvanized or any kind of primer applied until the surface of the inside of the pontoons are prepped. Now, if you can develop a process to clean and prep every square inch of the inside of the pontoons using only the 2" threaded bung hole, then your points about protecting the inside of the pontoons would have some validity. There is no doubt you know what you are talking about when it comes to coatings but application is the problem I see here.

Just look at my original pictures. One pontoon would have to have the oil removed and metal completely dry before any kind of primer would even begin to think about sticking. The other toon has a solid layer of surface rust which would have to be completely cleaned off the metal before any kind of primer would be long lasting.

You can talk all day about different kinds of coatings out there but there is only 2 ways I could see the inside of the toons getting that kind of treatment.
1. Fill the toons with a rust dissolver and let it sit for a while. Drain the dissolver and then fill the toons with acetone to rid the metal of the dissolver film. Then drain and dry, but then you have the issue of being able to apply a full, solid coating on the inside thru just the 2" hole. Just the chemicals alone to try and hopefully get all the rust gone would cost a fortune.
2. Cut a hole on the side of the pontoon big enough to get a person inside to prep the pontoon. But then you better worry about ventilation due to the enclosed space and so many other factors. Not to mention you just created another spot where your toon WILL fail in the future because after the coating is applied on the inside, and you weld the steel back on to cover the hole, you just burnt off that coating on the inside creating your fail spot.

But every steel pontoon on the lake has anodes. I don't think the inspector would pass a boat without one. Anyone who has ever worked on or owned a steel pontoon boat knows the importance of them. Don't forget to check the ones on your outboard motors or your lower drives also.

Just remember, the topic started with protecting the toons from the rust on the inside. The outside is the easy part.

After looking at it in this perspective, displacing the air with Nitrogen would definitely be more cost effective.

Happy boating. :D
 

Powelldreamer

Well-Known Member
But, since the inside of the pontoons are not protected and are, very possibly coated with rust, they can not be galvanized or any kind of primer applied until the surface of the inside of the pontoons are prepped. Now, if you can develop a process to clean and prep every square inch of the inside of the pontoons using only the 2" threaded bung hole, then your points about protecting the inside of the pontoons would have some validity. There is no doubt you know what you are talking about when it comes to coatings but application is the problem I see here.

Just look at my original pictures. One pontoon would have to have the oil removed and metal completely dry before any kind of primer would even begin to think about sticking. The other toon has a solid layer of surface rust which would have to be completely cleaned off the metal before any kind of primer would be long lasting.

You can talk all day about different kinds of coatings out there but there is only 2 ways I could see the inside of the toons getting that kind of treatment.
1. Fill the toons with a rust dissolver and let it sit for a while. Drain the dissolver and then fill the toons with acetone to rid the metal of the dissolver film. Then drain and dry, but then you have the issue of being able to apply a full, solid coating on the inside thru just the 2" hole. Just the chemicals alone to try and hopefully get all the rust gone would cost a fortune.
2. Cut a hole on the side of the pontoon big enough to get a person inside to prep the pontoon. But then you better worry about ventilation due to the enclosed space and so many other factors. Not to mention you just created another spot where your toon WILL fail in the future because after the coating is applied on the inside, and you weld the steel back on to cover the hole, you just burnt off that coating on the inside creating your fail spot.

But every steel pontoon on the lake has anodes. I don't think the inspector would pass a boat without one. Anyone who has ever worked on or owned a steel pontoon boat knows the importance of them. Don't forget to check the ones on your outboard motors or your lower drives also.

Just remember, the topic started with protecting the toons from the rust on the inside. The outside is the easy part.

After looking at it in this perspective, displacing the air with Nitrogen would definitely be more cost effective.

Happy boating. :D
I agree there are challenges with both ways. I am curious how you would be able to maintain the Nitrogen in the toons. We all know part of the issues are that the toons are not air/gas tight. That is the cause that leads to the internal corrosion. I have even thought just a good coat with WD 40 would work well in each section of the toon. I like the idea of the Nitrogen but see a lot of pitfalls with the pontoons as currently designed that do not make for a clear path forward.

:DOh the first world problems we have to deal with.
 

Dave I.

Well-Known Member
I agree there are challenges with both ways. I am curious how you would be able to maintain the Nitrogen in the toons. We all know part of the issues are that the toons are not air/gas tight. That is the cause that leads to the internal corrosion. I have even thought just a good coat with WD 40 would work well in each section of the toon. I like the idea of the Nitrogen but see a lot of pitfalls with the pontoons as currently designed that do not make for a clear path forward.

:DOh the first world problems we have to deal with.
First world problem is the simple fact the toons would have to be air tight, no exceptions. Supposedly, when you have your toons welded up at any facility that does the welding, they are supposed to pressure test them to insure they are leak free. Only then would the nitrogen make any sense. But the first time a seam splits due to, say a weld failure, the nitrogen would leak out and that money would be gone.

But that would be cheaper than paying a company $8000 for a sandblast, welding and recoat and the boat takes on water within 24 hours of getting launched, only to be told you have to pay for the whole process again if you want it fixed.

This has been an interesting topic and never expected it to go this far into detail.

What I get out of all this is to build new pontoons with new metal, treat the interior with some kind of protective coating, and then displace the oxygen with nitrogen and in theory, the inside of the toons should last forever. ;)
 

Squirrel

Well-Known Member
Being a mechanic for the last 40 years, I have found that the spray galvanizing compound works exceptionally well. Years ago I coated (1/2 way) a piece of raw steel with the galvanizing compound and placed it behind my shop. Years went by and the sprayed portion had no rust and the untreated side had pitted rust. I have used it in my shop constantly. My .02 cents. Sq. Add, I did this test to justify the cost, $7.50 per can, to my boss.
 
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Dave I.

Well-Known Member
Being a mechanic for the last 40 years, I have found that the spray galvanizing compound works exceptionally well. Years ago I coated (1/2 way) a piece of raw steel with the galvanizing compound and placed it behind my shop. Years went by and the sprayed portion had no rust and the untreated side had pitted rust. I have used it in my shop constantly. My .02 cents. Sq
Yes it does work well. But the metal does need to be clean and rust free to get the proper results like you did. But that is just about any coating if you want proper results. ;)
 
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