What Type Of Corrosion?

General boating discussion
Hunter24
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What Type Of Corrosion?

#1

Post by Hunter24 »

Can anyone tell me what type of corrosion this is? It is around the rivet near the bottom of the boat. I have a few more that are worse. This is on a 19’ aluminum boat. Thank you
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kmorin
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Re: What Type Of Corrosion?

#2

Post by kmorin »

Hunter,
I'd guess this was crevice corrosion where water could enter the paint film edge at the rivet perimeter and by capillary action fill the tiny void where the paint didn't seal the rivet edge to the sheet?

This small but common void is covered with a paint film but.... with hull use there is often microscopic movement fracturing the paint film- allowing water into the void are the edge of the rivet.

Once the water is present- it DE-aereates, has a ph shift and begins to lift the paint or primer bond from the edge. Eventually allowing larger areas of paint to lift off as they're no longer bonded to aluminum or primer but to a corrosion resultant compound. Very often when revealed and dried- the area will have a white chalky, powdery substance between the paint and metal.

There is a method of working on this - site by site to try to confine the damage to points of repair, if you want to get into the details?

Cheers,
Kevin Morin
Kenai, AK
kmorin
Hunter24
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Re: What Type Of Corrosion?

#3

Post by Hunter24 »

Is there anyway that this could happen on the side wall of the boat right at the water line and create a hole from the outside in instead of from the inside? On my other post you will see I found a few holes on the side of the boat that I am finally going to address this winter just hoping it isn’t from saturated foam and the Hull will be a mess.
kmorin
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Re: What Type Of Corrosion?

#4

Post by kmorin »

Hunter24 wrote: Tue Jun 07, 2022 11:40 am Is there anyway that this could happen

 
That's kind of hard to answer Hunter24.  Speculating about corrosion on a few photos is sort of low quality information (as a reply).

Since you know that once the internal foam is potentially involved you also know that you have to pull the deck and confirm the hull's interior surface conditions - so you've answered your own inquiry.  "IT" could happen from outside in but... you'll still have to 'know'; so you have to look inside to see what state your hull is in?

Cheers,
Kevin Morin
Kenai, AK
 
kmorin
Chaps
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Re: What Type Of Corrosion?

#5

Post by Chaps »

And my contribution to Kevin's knowledgeable response is to restate that manufacturers of riveted boats do not use marine grade alloys in boat construction and as such they are highly susceptible to various corrosion issues. Riveted boats have a short life expectancy when used extensively in salt water.
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Hunter24
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Re: What Type Of Corrosion?

#6

Post by Hunter24 »

kmorin wrote: Tue Jun 07, 2022 1:45 pm
Hunter24 wrote: Tue Jun 07, 2022 11:40 am Is there anyway that this could happen


 
That's kind of hard to answer Hunter24.  Speculating about corrosion on a few photos is sort of low quality information (as a reply).

Since you know that once the internal foam is potentially involved you also know that you have to pull the deck and confirm the hull's interior surface conditions - so you've answered your own inquiry.  "IT" could happen from outside in but... you'll still have to 'know'; so you have to look inside to see what state your hull is in?

Cheers,
Kevin Morin
Kenai, AK
 

 
Okay was just curious. Me and my dad talked about it and it is going to get torn apart this winter for sure. Went out yesterday and 2 of the noticeable leaking rivets you can now move
With your finger. So things need to get fixed sooner than later. Fix rivets/corrosion and paint by the looks of it.  
Hunter24
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Re: What Type Of Corrosion?

#7

Post by Hunter24 »

Chaps wrote: Tue Jun 07, 2022 9:50 pm And my contribution to Kevin's knowledgeable response is to restate that manufacturers of riveted boats do not use marine grade alloys in boat construction and as such they are highly susceptible to various corrosion issues. Riveted boats have a short life expectancy when used extensively in salt water.

 
Thank you for the knowledge and This is strictly a fresh water boat. 
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