Toon Acne

[selenag]

My toons have developed dime size white spots uniformly from front to back along at and below water line. Is this norma? It does appear to corrosion related but there is no visible metal loss. I am from Louisiana run in both river and lake water. I launch and retrieve only never leave in water for duration of use.

 

[WaterDR]

Re: Toon Acne

Few quick questions....

1 - Do you know the pH of the water where you use the boat?

2 - Are your toons galvanized by any chance?

3 - Have the toons been coated with anything like Sharskin or anything like that?

The photos look a bit like white rust which is essentially zinc-oxide. That is how galvanized metal corrodes and happens at higher pH levels. However, I am not aware of toons being galvanized. So, that is probably not it.

I would be more interested in the concentrtic patterns. This si more consistent with annodic attack in the center. I could tell in person if I looked at it, but it almost looks as if there is an annode in ther center (also looks rusty) and the white material is aluminum oxide. So basically, you have an electron transfer condition taking place.....like a battery. The center is the anode and is where the metal loss is taking place. The outside rings are acting as the cathode and is where the aluminum oxide is laying-out. If this is the case, it is a real problem. Why? Look at like this. Everywhere where you see a white pattern, that much mass is also being lost in the center. This will/can cause pin-hole leaks in the metal, but it not typically how aluminum corrodes. Makes me wonder if the toons were once coated and has lost the coating in places or if the alumium they used if of low quality.

Just to be clear.....crystal clear....aluminum does not rust. It can't. But, it does corrode. The by-product is aluminum oxide which actually is a corrosion protection barrier to further corrosion. People who clean and shine their toons are actually causing them to corrode further.

So, is this a big problem or not? I really can't say for sure. BUT, I would get a magnifying class and look in the center to see if you see any pitting. If you see noo pitting, then I would just say that the tubes are corroding and turning to aluminum oxide. I do see some pitting on the the photo you took of the back of the toon, though.

What does the zinc cathode look like on your motor?

It would also help if you knew the pH and Alkalinity of the water where you use the boat and if other people in the area have the same issues.

 

[selenag]

Re: Toon Acne

Went back out and looked and right around the transducer to the Humminbird depth finder there is very aggressive looking pitting. In fact We did not have this problem with this boat until this year after the dealer installed the new depth finder. Could this instrument contribute to this problem? I don't know the ph of lake water but will measure it when I get to the lake next weekend. I am also going to take voltage potientials readings with the depth finder on and off. I have included pictures of the pitted area and the anodes located on motor. I cannot find anymore pits anywhere else like what exist around the transducer.

 

[old jim]

Re: Toon Acne

Picture 2, is that something grounded to the boat? If so I don't think thats right.
Also check the wire to the transducer. Is it worn anywhere and touching the boat?
Regards, old jim

 

[WaterDR]

Re: Toon Acne

Pitting on aluminum like that is pretty unusual. It can be caused by something cased "stray current corrosion". It could be the hummingbird especially if it is not wired correctly. Something is causing the aluminum to be an annode. I would be curious to know if the mounting bracket is the same exact metal as the rest of the pontoon. When you have forced electric current the water itself (especially if it has a high conductivity) will act as the conductor. However, 12V is not a lot of potential and fresh water will not be very high in conductivity.

Again, I wonder what the zinc annode looks like on the motor? Is it pitted and white?

 

[selenag]

Re: Toon Acne

the wire is attached to anode and to bottom of pump for the trim......the wire to the transducer is free of cracks or damage but there could be something else where it was run back to the console. the boat is a 98 and I have never had anything like this till after the new depth finder was installed before this years boating. I am going to disconnect instrument when I go to the lake this weekend and see if these places start to oxidize and if they do I will know what is causing the problem.

Thanks for the response.

 

[WaterDR]

Re: Toon Acne

Can you take a picture of anode where the wire is attached? I wonder if that anode is toast and needs to be replaced.

 

[selenag]

Re: Toon Acne

I think I have found problem. Checking all grounds I discovered I have a ground that is common with hull. With key off, I disconnected all grounds attached to battery and with voltmeter attached to positive and pontoon I began to attach each ground, one at a time, until I got voltage. It is my main negative cable. I have to believe that this is not right and now I have to find where it is shorted. Meantime, when we are not moving I will have to disconnect from battery to minimize damage. This weekend is to important to me and my wife as my oldest daughter is coming in and along with my youngest and my only grandboy, Biddieboy, I am going to enjoy this weekend if it costs me both pontoons. I don't get to see her but once every year.

 

[5150abf]

Re: Toon Acne

I wouldn't worry about it too much this weekend, this happens very slowly over time so you can get it next weekend and don't need to disconnect the battery, enjoy your family.

Someone correct me if I am wrong but the engine is grounded so you will always have a small amount of current through the boat but you don't want to actually run a ground to the boat like a car does.