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Old 13-05-2015, 10:20   #1
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Removing bio stains from lower hull

Our Beneteau 49 has yellowish stains along the water line and up 2 feet. A crew getting ready to wash and wax the hull said "We will have to compound them out". I worry about damage to the gel coat and ask for advice in removing these stains in a better way.


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Old 13-05-2015, 10:22   #2
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Re: Removing bio stains from lower hull

Oxalic acid
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Old 13-05-2015, 10:29   #3
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Re: Removing bio stains from lower hull

Second the Oxalic acid. Cheap and easy to apply.
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Old 13-05-2015, 10:43   #4
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Removing bio stains from lower hull

On & Off, works very well.

Otherwise Compound, and Buff it out.
Unless your gelcoat is thin, and old.


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Old 13-05-2015, 11:00   #5
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Re: Removing bio stains from lower hull

No need to EVER compound it. Too much unnecessary work.

Ox acid, FSR gel, ketchup or lemon juice.

We call it the mustache.

Get it off, then wax, but only compound with a very light abrasive material if you must before waxing.

Your yard monkeys are ripping you off.

You can get it off in less than 20 minutes.
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Old 13-05-2015, 11:43   #6
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Removing bio stains from lower hull

Quote:
Originally Posted by Stu Jackson View Post
No need to EVER compound it. Too much unnecessary work.

Ox acid, FSR gel, ketchup or lemon juice.

We call it the mustache.

Get it off, then wax, but only compound with a very light abrasive material if you must before waxing.

Your yard monkeys are ripping you off.

You can get it off in less than 20 minutes.

I think if lemon juice and Ketchup worked well.
Every Yard Monkey would use that and make bank.
Sounds nice, but??
On & Off, it's ox acid.
If it's deep bio crud, your gonna compound and buff.
Cause without resealing the gelcoat by buffing it out and wax, it's gonna be as bad the next year or two.
You added that compounding maybe be required too.


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Old 13-05-2015, 12:17   #7
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Re: Removing bio stains from lower hull

Oxcilic acid or muratic acid and good coat of wax after
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Old 13-05-2015, 13:16   #8
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Re: Removing bio stains from lower hull

I've been happy with CLR (lactic acid), diluted about 10:1 and sprayed on.

All of the suggestions were weak acid cleaners, so you get the idea.

If they suggested compounding, I suggest you need to get another crew. They may be fixing to screw up your boat. They know NOTHING about cleaning and boats.
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Old 13-05-2015, 13:30   #9
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Re: Removing bio stains from lower hull

I would exercise caution when using lactic acid. It has been shown to cause development issues to outright mortality in fish
Chemical Toxicity Studies on Fish Chemical Toxicity Studies
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Old 13-05-2015, 14:10   #10
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Re: Removing bio stains from lower hull

Oxalic Acid CRYSTALS via a Sand Blaster should do the trick nicely Kidding.

You, not the yard guys, might want to try a light pass, in a Small area, with either; Vinegar (Acetic Acid), or Soft Scrub. Followed by a good rinse.

Just out of curiosity, have any of the following been tried? A pressure washer (especially the type which you rent locally), or a few different formulations of soaps/cleaners using a good stiff scrub brush.

My thinking is to start mild, & work your way up. As the more potent the chemicals, or when the power tools start coming out, the likelihood of doing damage definitely starts to climb.
Also, do you have any insights as to what might have created the staining in question? The reason I ask, is that as often as not, if you know, from a chemistry standpoint what caused things, then you may be able to use it's (mild) chemical opposite to remove them.
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Old 13-05-2015, 14:23   #11
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Re: Removing bio stains from lower hull

Stop the FUD, there's no lactic acid in CLR.

http://emergencyservices.catawbacoun...f/MSDS/CLR.pdf

See for yourself.
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Old 13-05-2015, 14:33   #12
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Re: Removing bio stains from lower hull

We use CLR with a magic eraser to remove our mustache.
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Old 13-05-2015, 16:19   #13
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Re: Removing bio stains from lower hull

The magic eraser "is" a 3000 grit sandpaper block, actually. A very carefully chosen brittle foam plastic, that breaks down into a slightly abrasive powder similar to 3M Finesse-It polish. Terribly clever idea, but "sandpaper" not "magic".<G>
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