So this story blew my mind…
A friend of mine went to sell his alum Jon boat after he hasn’t used it much the past year.he put it in the water to sea trial with a potential buyer. He noticed water was coming through a very small hole in the middle of the boat. Sea trial went fine, buyer didn’t really care to much. Took it out of the water and apparently where the carpeted trailer bunks touched the bottom of the hull, it had almost deteriorated through! He spoke to a dealer somewhere that said the carpet along with saltwater and aluminum caused it to rust by electrolysis. Is this for real? Where these components made that happen? This ran the length of the bunks and pretty much made the boat unrepairable. It seems like every Jon boat is on a trailer with carpeted bunks. I had another buddy mention it was due to treated lumber being used. I was in the market for a Jon boat , this points me right back to a smaller fiberglass skiff… Any input from the boat gurus around here would be much appreciated.
Doubt it was carpet that caused it.
I found out first hand about electrolysis. No reasonable explanation, no loose wires and not left in water. I will never pay good money for a tin boat again.
I’ve seen that happen myself. I think it’s due to the chemicals in some pressure wood. Anytime you have 2 dissimilar metals separated by a dielectric you create a battery effect with a current flow from negative to positive. That causes erosion on the negative anodic side.
The pressure treated wood probably has a chromated copper base. The carpet bunks trap salt and moisture, a dielectric between the aluminum boat which is the negative, anodic side and the copper. The aluminum acts an anode to the copper causing it to erode, just like a zinc anode does on aluminum or bronze.
Put down a layer of heavy plastic on the wood to act as an insulator before putting down the carpet. Use carpet that doesn’t absorb moisture also, not carpet store remnants.
Capt. Larry Teuton
Cracker Built Custom Boats
“Ships are the nearest things to dreams that hands have ever made.” -Robert N. Rose
Larry, how often are these Jon boAt trailers sold without the heavy plastic layer? The trailer was less than 3 years old. I would have never thought of thAt until it was to late. What about those plastic bunk sliders that help reduce friction,would these help?
im not to sure, but im pretty sure…
Have had bunk slicks on mine for years and no issues. Had a friend who looked at buting used Jon and found the same issue. Said always slide Jon to one side and check for electolysis along bunk runs.
quote:
Larry, how often are these Jon boAt trailers sold without the heavy plastic layer?
Probably almost always. The good news is that most newer pressure treated woods don’t use copper anymore, an EPA thing I think.
The plastic bunk slides will solve the electrolysis problem but they are too slick for my likes. Some people like them.
There is really no reason to use PT wood but most manufacturers do. Good quality southern yellow pine, cypress or douglas fir, coated with 2 coats of epoxy and wrapped with plastic carpet will last almost forever without any electrolysis. Replace the carpet every 8-10 years.
Capt. Larry Teuton
Cracker Built Custom Boats
“Ships are the nearest things to dreams that hands have ever made.” -Robert N. Rose
Electrolysis is caused by DC (Battery) and saltwater causing a non-spontaneous chemical reaction. The carpeted bunks hold saltwater each time you load/unload the boat. The battery and other electronic components are grounded to the boat frame (aluminum) and this interacting with the saltwater causes non-spontaneous chemical reaction (corrosion). This is why there are sacrificial (zinc) anodes on motors. I have discusses this topic with others and resolutions were things like plastic covered bunks and disconnecting the battery when not in use.
Teflon slides should cure the problem. I have them on both my Jon boat trailers and never had a problem.
However…
I once had a light mounted on a PVC pipe for shrimping. My buddy noticed the arcing at the bottom of the pipe where it contacted the floor of the boat. Long story short, the toggle switch for the light (which was mounted about half way up the pipe) was conducting back down the pipe to the boat floor. (because everything was covered in salt water) That thing almost blew a hole in the bottom of the boat.
218WA Sailfish
The "Penn"sion Plan
I lost my old jon boat to trailer bunk electrolysis. When I got the new boat I replaced the bunks on the trailer and instead of carpet I used overtons plastic bunk covers. They are not very slick like some of the other ones on the market. 2 years and electrolysis free!
Wow. good to know. this boat was a pull start and had no battery or electronics. Trailer lights possibly?
im not to sure, but im pretty sure…
I have a friend that may have this issue with his war eagle. If caught early enough can the boat be saved or will it continue to have corrosion issues in the affected areas?
“Work is for people who don’t know how to fish”
2005 180 Flats Fox w/115 Yamaha 4 stroke
1996 1436 War Eagle w/25 Evinrude 2 stroke
No battery is needed to have this problem. Any two dissimilar metals connected and put in a conductive solution (e.g. salt water) will have this problem. One will give up material. The other will gain material. Loading an aluminum boat onto wet carpet bunks that are connected to a steel or aluminum (the aluminum in the boat will not be the same alloy as that in the trailer) trailer is all you need. This does not happen in fresh water nearly as much as salt since fresh water is a poor conductor. Putting a battery in the mix may accelerate the dynamic, but, a separate battery is not required to have significant electrolysis. The more dissimilar the metals are, the more electrolysis you get.
17’ Henry O Hornet
26’ Palmer Scott
Just to set everyone straight, the corrosion is galvanic, not electrolysis. Electrolysis involves an impressed current whether intended or not. The outside of the hull of a aluminum boat is not going to be subject to it even if there is current running through the boat as it will take the path of least resistance through the hull back to the battery ground.
Galvanic corrosion is two dissimilar metals in an electrolyte which allows the free exchange of electrons…this is a battery. The less noble metal (anode) gives up its electrons to the more noble metal (cathode).
It is likely a combination of chemical attack from the wood and crevice corrosion. Aluminum, like stainless steel, stays mostly corrosion free by forming a very thin oxide layer. The layer can only form in the presence of oxygen. If the metal is in an area devoid of oxygen and there is a break in the surface oxide (that would happen on a trailer bunk) corrosion can occur uninhibited.
Like mentioned, slick trailer bunks will solve the problem.
Iain Pelto
Sea Hunt Triton 160 w/ 90 ETEC “JB3”
Native Manta Ray 14
quote:
Originally posted by hairballJust to set everyone straight, the corrosion is galvanic, not electrolysis. Electrolysis involves an impressed current whether intended or not. The outside of the hull of a aluminum boat is not going to be subject to it even if there is current running through the boat as it will take the path of least resistance through the hull back to the battery ground.
Galvanic corrosion is two dissimilar metals in an electrolyte which allows the free exchange of electrons…this is a battery. The less noble metal (anode) gives up its electrons to the more noble metal (cathode).
It is likely a combination of chemical attack from the wood and crevice corrosion. Aluminum, like stainless steel, stays mostly corrosion free by forming a very thin oxide layer. The layer can only form in the presence of oxygen. If the metal is in an area devoid of oxygen and there is a break in the surface oxide (that would happen on a trailer bunk) corrosion can occur uninhibited.
Like mentioned, slick trailer bunks will solve the problem.
Iain Pelto
Sea Hunt Triton 160 w/ 90 ETEC “JB3”
Native Manta Ray 14
</font id=“quote”></blockquote id=“quote”>Thanks, for that information/clarification.
By the way… is this electrolysis or galvanic corrosion?
That is some good info, thanks for clearing this up. Now if this rain would go away we could get on the water!
im not to sure, but im pretty sure…