CORROSION!!! And lots of it.

General boating discussion
Rockfisher62
Posts: 3
Joined: Thu Apr 21, 2022 11:28 pm
1

CORROSION!!! And lots of it.

#1

Post by Rockfisher62 »

I was going fishing last week, then I noticed a foul odor from my boat.  I thought a battery tipped over. Nope.  I took everything apart and found the source of the smell.
Crap under the fuel tank prevented water and everything else from running out the back. 
What would you guys do with this?
There are about 8 through holes from the size of a pin head to a 1/2".  I guess the fuel tank sitting over the holes also kept the boat from sinking!!
Can this be TIG welded?
 
 
Attachments
2006 Alumaweld Talon.jpg
2006 Alumaweld Talon.jpg (99.49 KiB) Viewed 2813 times
1 under fuel tank.jpg
1 under fuel tank.jpg (82.3 KiB) Viewed 2813 times
02 Multiple Holes.jpg
02 Multiple Holes.jpg (30.83 KiB) Viewed 2813 times
Hole scale.jpg
Hole scale.jpg (43.27 KiB) Viewed 2813 times
Close up.jpg
Close up.jpg (56.03 KiB) Viewed 2813 times
User avatar
welder
Site Admin
Posts: 4667
Joined: Thu Jan 03, 2008 11:51 pm
16
Location: Whitesboro, Texas
Contact:

Re: CORROSION!!! And lots of it.

#2

Post by welder »

Yes, easy to repair.
Cut out or drill out to clean material, patch and reweld
Lester,
PacificV2325, Honda BF225
2386
Chaps
Donator '09
Posts: 2246
Joined: Sun Jan 13, 2008 12:19 am
16
Location: Seattle, WA

Re: CORROSION!!! And lots of it.

#3

Post by Chaps »

Hire a pro to do the job,  I agree with Les that it can be done but it can be tricky as the corrosion can affect the hull metal in ways that only an experienced welder will know how to handle.  I've watched 1/8" holes quickly get blown out to bottle cap size by a mobile dude who quickly packed up his stuff and high tailed it.
1987 24' LaConner pilothouse workboat, 225 Suzuki
Image
please view and like: https://www.facebook.com/bottompainting/
Rockfisher62
Posts: 3
Joined: Thu Apr 21, 2022 11:28 pm
1

Re: CORROSION!!! And lots of it.

#4

Post by Rockfisher62 »

Thanks for the input.
I called 7 different weld shops in the Sacramento, CA area and the only one who offered to come look at it was a mobile welder. The others didn't return my call, were too busy, or just said they didn't want the hassle associated with a corroded hull. I wondering if I should let him touch my hull.
kmorin
Donator 08, 09, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24
Posts: 1735
Joined: Mon Aug 18, 2008 1:37 am
15
Location: Kenai, Alaska

Re: CORROSION!!! And lots of it.

#5

Post by kmorin »

Rock'62,

Portable TIG is somewhat compromised over shop TIG due to the power supply requirements and the most common solutions to that equation.  I'd spend most of my time, were I in your shoes, working to get the skiff seen by a shop, in their own facility.   You can save yourself some of the costs by cleaning the holes to bare metal.  I'd suggest a carbide burr for non-ferrous applications which has very distinct flutes and is not cross hatched in the cutting flutes.

Clean out the openings and if you have to get to an opening of larger than 1/2" dia. ?  then find/cut solid round stock or pieces of plate to fit into the holes you've cut.  Any opening smaller than 3/8" could just be drilled out (if the surrounding corrosion is cleaned out by the bit?) and TIG welded closed.

Not mentioned is the underlying source of the corrosion?  Was the bilge acidic?  It appears to have been?  It's surely good practice to put a box of baking soda (base) into a bucket of warm water and flood the bilge and rinse the entire boat at the end of a season in order to neutralize any acidic bilge water remaining from a season of organic decomp. in the bilge water.  IF you pull the drain plug, elevate the trailer tongue and don't get a bucket of bilge drained?.... investigation is in order.

cheers,
Kevin Morin
Kenai, AK


 
 
 
kmorin
Rockfisher62
Posts: 3
Joined: Thu Apr 21, 2022 11:28 pm
1

Re: CORROSION!!! And lots of it.

#6

Post by Rockfisher62 »

Kevin,
I've always resisted cutting the structural cross-member that kept the tank from being removed, but, the acidic smell was so strong I had to do it when I found the holes.
I removed the tank, scraped the bilge organic decomposition, scrubbed it with simple green, stainless cup brushed it(new brush), then pressure sprayed it.  Then I taped up the holes from the outside and mixed a box of baking soda with 3 gal of water and poured it in and let it stand for 3 hours.  Then I drained it and rinsed it with the hose.
I'll build a bolt in tank retainer so the tank can be removed in the future. I'll also find a way to elevate the tank off the bottom to allow the flow of water under it. 

What should I do with the surface pitting that is .020-.060" deep? I'm concerned about dirt/organics collecting in the pitting and causing future corrosion.  I don't want to pull the tank after every trip.  Maybe epoxy? Or just leave it & flush it twice a year?



 
 
 
 
 
Attachments
Tank in place2 .jpg
Tank in place2 .jpg (71.6 KiB) Viewed 2752 times
Tank out.jpg
Tank out.jpg (99.89 KiB) Viewed 2752 times
Cut crossmember-tank removed.jpg
Cut crossmember-tank removed.jpg (88.92 KiB) Viewed 2752 times
IMG_20220420_102306828.jpg
IMG_20220420_102306828.jpg (269.32 KiB) Viewed 2752 times
kmorin
Donator 08, 09, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24
Posts: 1735
Joined: Mon Aug 18, 2008 1:37 am
15
Location: Kenai, Alaska

Re: CORROSION!!! And lots of it.

#7

Post by kmorin »

Rock'62,
I'd remark about the newer photos in context of the first set you posted. 

1st.   I'd say there might be two separate but related instances of the corrosion in your bilge.  One seems to be the concentrated material that resulted in a very wide patch uniformly corroding the entire area of the hole and the hole itself?  This seems to me to be a causal site- or one where a concentrated acidic cell was working?

2nd. The less concentrated but still widely spread corrosion sites seem to be the result of a bilge water ph that was too low; so the sites began to corrode smaller in (each) area but more wide spread in distribution of sites.  I'm inferring there was a concentrated mass of 'poultice' in the case of the holes and likely a less concentrated but just as acidic solution in the remainder of the bilge water and its effect on the bottom plate.

You can't be sure of eliminating all the acidic pockets of material down in those many corrosion cells- even using a base solution to flood the area?  However, that is about the best preliminary step I know about- you might want to let the neutralizing solution sit longer in the bilge- won't hurt the metal or other components- or repeat the process several times.  Also household ammonia is a base that will help shift the ph back to ranges that aluminum can 'stand'- so it can be used in the neutralizing wash water mix.

Once  you've neutralized and rinsed and repeated, you've done what you can in terms of cleaning out the pockets - unless you dig them out with a carbide burr- which is lots of work as you can see.  The wire brushed area looks very well recovered of corrosive residue (which, if left, has the needed chemistry to help the cell become active again) so that works where the corrosion cells have left the top open to be excavated.  I did an article here somewhere showing some corrosion cells I found doing a bottom repair (not unlike this one) in other boats.  There are 'internal' cells that don't show up too well and were a real pain-in-the-stern to weld!

I'd like to know (if it were my skiff) what the two outer hull areas look like?  If the bilge water could stand under the tank and pit the hull plate- it might have reached out under the foam in the hollow longitudinals and outboard between the next longs outboard toward the chine?  Looks like foam there too?  What does that hull area look like?

I try to avoid using Simple Green on aluminum as the MSDS specifically mentions there are compounds of copper in that soap & they don't recommend use on aluminum.  If well rinsed it may be OK (?) but I'd avoid anything with copper traces for use on aluminum.

Once the bottom is cleaned by the various methods discussed here- an epoxy paste/filler could be troweled on and then a bottom paint or coal tar bilge paint applied to try to keep the bilge water from reactivating at left over corrosion cell sites.

Getting the holes welded closed and perhaps 'floating' a few of the deeper looking pits inside the area shown- will help you decide if more drastic hull metal work is needed? By this I mean that we've see boats where the area corroded needed a doubler plate welded on to insure integrity of the metal that had been corroded in a wide area of pits- some through some not- but the entire bottom was 'swiss cheese' pits all over. If that shows up in your case (?) then it may be necessary to bend  pc of 1/8" or 3/16" the shape of your bottom deadrise and plate the centerline/keel for a few feet under where the main corrosion pitting and holes are located.

Hope this review helps? I'm pretty sure there are other similarly designed boats of the same size range on the Forum for identical problems in the last couple years so researching those posts/threads would likely help with your planning.  Also, finding those members and contacting them about what they did- or did not do- and what their results were from their work recovering from corrosive bilge water might be helpful in your plans for your boat?

Last note:  Reviewing the first set of pictures, I see the trailer has bunks and wondered if they're covered with carpet or plastic bunk 'wraps'?  We've also seen, here at the Forum, more than a few instances where carpet covered trailer bunks promoted crevice cell corrosion of the hull because the carpet stays 'wet' and allows the very thin layer of water to shift ph , by de-aeration and start pitting on the bottom of the hull similar to that shown inside the hull.  That condition is referred to as 'bunk rot' and is fairly widely understood but is cured by covering the bunks with the plastic bunk covers that won't hold water like carpet does.

cheers,
Kevin Morin
Kenai, AK  
 
 
 
Last edited by kmorin on Sat Apr 23, 2022 3:32 pm, edited 1 time in total.
Reason: Bunk Cover remarks
kmorin
Post Reply Previous topicNext topic