New guy here with corrosion.

General boating discussion
NW_Nelson
Posts: 2
Joined: Mon Feb 22, 2021 6:20 am

New guy here with corrosion.

#1

Post by NW_Nelson »

Hey AAB, new to this forum and alloy boats. I recently picked up a 1997 Alumaweld Stryker. Unfortunately, it has sat outside for over 2 years here in western WA. I have spent hours reading on this forum about corrosion and what to do. I thought I would reach out and see if the plan I have come up with is the best procedure. I’ll add some pics as well.
First step I’m obviously removing the foam (not sure if any will be going back in). The corrosion in the bilge so far does not seem that bad but want to make sure it’s treated properly. I plan on sanding the bilge with scotch brite to clean all the junk off. Then sand blasting the corrosion areas and acid etching the whole bilge. I would like to apply an epoxy coating to the bilge, any recommendations? As far as the box stringers, that’s where I have found the most. Would it be best to cut out the bad sections and have new welded in or am I ok to treat and coat? Thanks for the help.
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kmorin
Donator 08, 09, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21
Posts: 1589
Joined: Mon Aug 18, 2008 1:37 am
Location: Kenai, Alaska

Re: New guy here with corrosion.

#2

Post by kmorin »

NW_Nelson,
First, welcome to the AAB Forum, and I hope you're able to find out how best to repair your boat.

The picture of what I assume is the bottom plate/panel shows some spots of corrosion but not too much in detail regarding depth. That seems the most important to learn? drilling the tops of some of those sites/spots/pits will open up the tops to see how extensive they are? Not saying you'd drill through, just a large bit used to cut the sides a bit to discover the bottom depth?

The second picture is of a stringer/longitudinal if I understand? That does seem like quite a bit of deterioration and uniformly corroded surface, if this extensive corrosion is limited to a few locations? then maybe cutting those areas out and replacing them is best - but its hard to suggest w/out seeing the extent? If much of those longs look like the picture? Then what's under them might be as bad or worse?

I think getting them cleaned up - inside and out is important based on the condition of this section. Not sure the boat's overall design? but even if this implied some extensive rebuilding removing parts with this level of corrosion would A) allow full inspection and repair under the longs/stringers; B) allow the hull to be returned to original strength with new material; C) allow any decking to be installed correctly- where this image suggests that was not the case in the original build?

I have seen decks mounted to hull longs without any coating or bedding do this to the tops of deck beams/hull frames. These were plywood decks where the water could stand on the top of the framing piece- and be chemically 'treated' by the wood! Not the best design when a bit of 'ice & water shield' adhesive film would keep the two materials from being in contact with one another - act as a bedding for a wooden deck. Many decks are screwed to the aluminum framing w/o any bedding to help seal the threads leaving a path for water to enter and help along the galvanic cell formed. But the sticky mastic will also help line the self-tapping screw by sealing the perimeter when the fastener is driven through the film into the metal below.

If you had time to show a few more photos? maybe giving a bit more context? close ups are helpful but images with a wider field of view help put the detail shots in perspective.

Cheers, and welcome to the AAB Forum,
Kevin Morin
Kenai, AK
kmorin
NW_Nelson
Posts: 2
Joined: Mon Feb 22, 2021 6:20 am

Re: New guy here with corrosion.

#3

Post by NW_Nelson »

Kevin,
Here's a better pic of what I'm working on. I just realized why the top of the stringers is so bad in those two locations, pedestal mounts. Plus there was no bedding for the plywood deck.
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I have not uncovered all of the pits yet but so far there is only 2 spots that might be about half way through the hull. The pitting is in the center bilge area. I haven't gotten all of the foam out of the stringers but the only pitting I have found is under the holes where the pedestal mounts were. Which is surprising to me considering the amount of water in the foam. From what I have seen on other posts and searches, I'm not in too bad of shape with my corrosion. I've read enough to make my head spin. I just want to make sure I'm doing this right and the best possible way.

This is pretty much a restoration project. Only things not being replaced is the outboard, control box and wiring. Everything else is being replaced. I'll be doing it all except any welding I may need.

Here's a couple more pics of the boat. Including a shot of when I first took the deck out.
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I'm brand new to using these forums and posting pics. Not sure how clear they are.

Thanks!!
Ryan
kmorin
Donator 08, 09, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21
Posts: 1589
Joined: Mon Aug 18, 2008 1:37 am
Location: Kenai, Alaska

Re: New guy here with corrosion.

#4

Post by kmorin »

Ryan,
yessiree! that boat had some thick organic compost for bilge water!! That stuff can really get after aluminum.

The two stringer boxes do show lots of local corrosion where the pedestal cross pc was located. This is classic crevice corrosion (poultice corrosion) where water is left to become acidic and does so, every time it rains, or takes more water the cycle is renewed and more of the stringer box top would be given up to this endless corrosion cell.

At this juncture, can't hurt to mix up some ammonia water or some baking soda water and rinse your entire bilge, at least that solution would help to neutralize any remaining acidic sites down in the pits - they're working 24/7 unless neutralized with some base solution.

lots of work ahead of you... I'm old and lazy and hardly even look at projects like this one! Too much goop and goo to be worth doing. Good luck, let us know if you have more questions? Someone here will take a shot at an answer.

Cheers,
Kevin Morin
Kenai, AK
kmorin
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