Oil as corrosion prevention in bilge?

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skypoke
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Oil as corrosion prevention in bilge?

Post by skypoke » Thu Jan 26, 2017 11:15 am

I've got my 28' powercat on the bench for some refreshing. Due to a failed partnership, the boat sat at ex partner's place for a couple years, batteries on, freshwater collecting along with leaves, fishhooks and bilge pumps leaking current. So, some corrosion on inside of 6mm hull plating though only a few deeper pits. Following the large amount of infomation gleaned from similar posts, and working on channelling Kmorin, here's the plan:

Clean, clean, clean. Vacuum up any visible debris and inspect.
Burr out any significant pits, chasing corrosion to clean metal. Carbide burr.
Tig weld pits, taking special care to work from edges, floating any contamination out.
In the event a pit is located that is impractical to tig, cut it out with a hole saw, insert sawn coupon, tig seal weld from both sides. I'm thinking this can avoid the need for a doubler?
Clean again.
Acid wash. Flush with copious fresh water. Neutralize with water/ammonia solution.
Allow hull to thoroughly dry.

At this point, I would like to apply a coat of LPS3 to the inside of bilge. While I will take every precaution to follow good electrical practice, it has not proven to be good enough to avoid corrosion. Of course, benign neglect had a whole lot to do with these problems popping up and this won't happen again. I'd appreciate any thoughts on the advisability. The only downside I can see is that it will greatly complicate any future welding but this can be dealt with. The entire hull(s) will be inspectable with lift up floorboards, except for below fuel tanks. I do have the services of a very capable Tig welder available.

I appreciate your help on this.
Texian, born and bred.

welderbob
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Re: Oil as corrosion prevention in bilge?

Post by welderbob » Sun Apr 23, 2017 1:55 pm

try Corrosion X, they spray it inside airplane to prevent corrosion. You can buy it a gallon container.
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kmorin
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Re: Oil as corrosion prevention in bilge?

Post by kmorin » Sun Apr 23, 2017 4:17 pm

welderbob, skypoke, there is another similar product that Boeing helped develop with Lear Chemicals (I think?) named ACF-50? I could be off in this name? But it's used inside aircraft assemblies where it's hard to get access to clean- and even designed to flow into existing pits and corrosion sites- arrest the corrosion and preserve an oxide film.

Now most aircraft aren't 5000 or 6000 series aluminum so my recommendation of this product is more a suggestion to look it up- read the application literature and the MSDS and then consider its use?

But if you have bilge areas that are hard to access- like the inside of an airplane wing is hard to access- this was developed to arrest corrosion.

Cheers,
Kevin Morin
Kenai, AK
kmorin

skypoke
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Re: Oil as corrosion prevention in bilge?

Post by skypoke » Sat Jun 17, 2017 5:06 pm

A bit of follow up here. I'm happy to say the corrosion pits were localized and relatively easy to grind out and tig up. None were deep enough to require plate replacement. We're going to move ahead with the refit and relocate the boat to our place on the olympic pen.

It doesn't yet, but will have, a waxy coating of LPS3 in the bilge. I've seen the effectiveness of this stuff through my years on the hypersaline gulf coast, and am convinced it will do the trick. Thanks all for your input.
Texian, born and bred.

MacGyver
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Re: Oil as corrosion prevention in bilge?

Post by MacGyver » Tue Jun 20, 2017 2:08 pm

When applying any of the anti-corrosion product the metal must be dry and clean of any dirt. Depending on the brand and where it being used it has to be refresh every 6 months to a year. That may not be possible in the bulge. Before using any anti-corrosion product make sure there is NO oil film that can get into the water.

kmorin
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Re: Oil as corrosion prevention in bilge?

Post by kmorin » Thu Jun 22, 2017 4:22 pm

Mac, reading the ACF-50 Boeing 'oil' lit and talking with an A&P mechanic who introduced me to the compound; all indications are this material will work on totally corroded aluminum- with dirt and dust and junk coatings- it follows by capillary action- the contour of solid metal and interacts at that surface- regardless of how deep under contaminates that surface lies.

So while cleaning then coating is better due to reduced amount of oil/penetrant needed- this particular product was designed to be sprayed into airplane cavities that can't be reliably cleaned- and still do its job.

I have seen it applied to pitted corrosion sites on small castings that were not sandblasted or cleaned. When the pits were then cleaned out- there was the ACF- in the bottom of the pit coating the underlying metal? http://learchem.com/products/acf-50.html I have not used this in a boat bilge but it seems like it would be effective - especially in places hard to access or locations where really effective cleaning was NOT easily done.

Cheers,
Kevin Morin
Kenai, AK
Last edited by kmorin on Tue Oct 03, 2017 7:05 pm, edited 1 time in total.
Reason: forgot word "NOT" !
kmorin

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Re: Oil as corrosion prevention in bilge?

Post by JETTYWOLF » Tue Oct 03, 2017 1:59 pm

had exactly that, too! from months of stray current. pitted the bilge area BIG time. power washed whole area with detergent, washed with power sprayer again. with just water, then air dried with fan, even. not needed in the heat of florida, but area was bone dry. Got Corrossion X and sprayed entire effected area...THICK. so much that it puddled in front of the bilge drain hole. Plan on doing again. via a gallon of Corrosion X. And let it just slosh around down there.

Believe the stray current is now fixed, via testing. But want to arrest continued pitting. Or just for a "state of mind" feeling, at least. Don't believe it would hurt anything.

skypoke
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Re: Oil as corrosion prevention in bilge?

Post by skypoke » Sun Oct 22, 2017 9:31 am

Well, everybody has their own secret sauce, and as Kevin says, the ACF50 is well proven in aircraft use. That said, I'm sticking with the LPS 3 as it is durable....it forms a waxy, greasy, self healing coating that firms up and does not evaporate, and I've used it on electrical items that are exposed to salt spray during my tenure as a tech at a marine science institute. It ain't pretty, but it does work, and it survives extended immersion. I have also, as a matter of course, thoroughly, multiple coated every outboard powerhead I've owned, and ten years later they are still like new under the coating. So, on it goes, along with the sincere hope that I don't ever have to weld any of the coated parts! (It is removable, with solvents and effort.)
Texian, born and bred.

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