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Old 30-05-2020, 05:48   #1
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Fixing sloppy silicon job

Anyone have any ideas on how to get this silicone off the deck? The last owner clearly didnít care much for finish work. I just refinished on the teak handrails, which look good, but now this nasty blackened silicon job really stands out.

Iíve tried scrubbing it with an array of bushes and soft scrub to no avail. Any suggestions would be much appreciated!

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Old 30-05-2020, 06:02   #2
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Re: Fixing sloppy silicon job

Ahoy, welcome to CF.
The woodwork looks nice, congrats.
Is it possible to unbolt the handrail and get underneath?

My pet peeve on RV's and boats is silicone. It usually means there was a leak and someone did not want to take the time to remove the hardware, re-bed with butyl mastic, and replace the hardware the correct way. Butyl usually cleans up/ cleans off easier than silicone too.

The other thing to check is for water damage around the holes drilled to mount the pieces to the deck.

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Old 30-05-2020, 06:27   #3
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Re: Fixing sloppy silicon job

The issue with silicone is that it leaves some kind of oil behind and I don’t know of a way to get that off, and this residual oil interferes with other sealants adhering.
I would remove the trim and use GE SCS 2000 sealant. It is a silicone type of sealant but is very different than regular silicone caulk, for one it’s thicker and has no vinegar smell, it also comes in many colors, the last digit changes according to color. It is an outstanding sealant for chainplates and anywhere there may be a lot of movement, 5200 is watery and very difficult to keep from running and if there is any movement, it’s not a good sealant. 4000 is similar but your real problem is the oil silicone leaves behind.
The SCS 2000 is used to glue windows onto skyscrapers.
If you can’t remove the trim, dig out the old silicone the best you can using an exacto knife or similar and put the SCS 2000 over it, it should adhere well, but other sealants probably won’t.
You really should remove the trim if possible as you really want to ensure there are no leaks in the deck cause if there is even a small one it will cause a great amount of grief in the future.
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Old 30-05-2020, 06:31   #4
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Re: Fixing sloppy silicon job

Re-Mov does a very good job of removing silicone, but used in this kind of situation it will also break the bond. You might try a 3M adhesive eraser. Otherwise, you'll have to wait until you are ready to re-bed the rail.

Re-Mov removes the silicon residue as well and allows for good bonding. I have tested this. Good stuff, I was surprised.

There are good uses from silicone, this just isn't one of them.
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Old 30-05-2020, 06:56   #5
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Re: Fixing sloppy silicon job

What you show in the picture is a typical reaction by amateurs to a leak. Smear something all around it. Ir (and its a big if) it stops the leak it doesn't last long, no matter what you use.

If there is a leak in bedded hardware, the ONLY way to fix it is to pull it up and rebed it from scratch. As painful as that might be. Spreading cake icing around the joint on the outside just doesn't work, and it looks ugly, and points out to any future buyer right where the leaks are.

Really would have been best to fix this BEFORE the revarnish job, but you are where you are.

If what you have really is silicone, it should peel off fiberglass with patience and care. We use wooden or plastic scrapers and it comes of not exactly easily, but it does.

Are you 100% sure it is silicone? If it is 5200 or other polyurathane you have a much bigger job. Mechanical removal is still possible, but it sticks a LOT harder. Usually the best PU's to get them off is to use a solvent made for the job. The problem here is any solvent will attack the sealant under the joint.


GE SCS2000 is great stuff and I use it all the time for sealing and glueing in windows (plastic and glass). For complex fittings, its longer open time is a great help. But it most certainly IS real silicone. Neutral cure, not acid cure, but if you are concerned about residue after removal, it leaves the same stuff behind, and needs just as rigorous cleaning for the best bond. SCS2000 is essentially the same as Dow 795. One downside of the neutral cure silicones, is that they are rarely available in a "clear" formulation.

We have found the solvent formulation in Goof-Off to be great at cleaning up any area that had sealant on it before rebedding. Does it remove 100% of contaminants? I don't know, but I have never had a bond fail--so good enough.
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Old 30-05-2020, 09:05   #6
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Re: Fixing sloppy silicon job

Gasoline will dissolve silicone, and it's cheaper than the other stuff. Wear gloves and make sure the area is ventilated.
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Old 30-05-2020, 09:08   #7
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Re: Fixing sloppy silicon job

Silicone takes a lot of work to remove. I agree with other posters that it should not be used on a boat deck but if your PO was like mine, it's all over the place.

I've yet to see a product that does a good job removing silicone, so mechanical removal with a razor blade along with some solvent to help things along is the only thing that I've found that works.

First choice would be to remove the handrail, clean and re-bed. This might be something you want to avoid, but it's what's needed, and with a boat your effort and cost will always be much more if you take short cuts.

Either way, here's the protocol I've developed over the years-
Step 1. Tape around your work area so you don't do more damage than necessary.

Step 2. Use a razor blade (on a scraper with a handle) and slowly, gently scrape and peel the silicone off, taking great care not to scratch the gelcoat. Totally possible, takes finesse and a long, long time to do it well.

Step 3. When you have scraped off as much as possible, use acetone and a light scrubbing pad (white is least damaging) to clean and highlight the residue (use gloves).

Step 4. Silicone residue can be hard to see, so once it's highlighted from step 3, scrape again.

Step 5. Repeat 3 and 4 a million times until you can no longer feel residue (with your gloves off) and acetone no longer highlights any residue. It's amazing how stubborn silicone can be.

Final steps: remove tape, re-bed your fitting and re-wax the area you used acetone.
This is a PIA but I haven't found any product or technique that does the job any better.

As you might see, it would be easier and better in the long run to remove the handrail to clean the silicone and re-bed correctly, than it would to work around the handrail to remove the silicone, after which you will have a possible leak you'll have to take care of (or ignore for the next owner to cuss about).
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Old 30-05-2020, 09:32   #8
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Re: Fixing sloppy silicon job

I recently pulled up some boat stanchions that a previous owner had sealed with silicone.

I was prepared to use some DAP Home Depot Silicone remover as I have in the past but it's slow and only partially effective.

After trying a number of solvents I found a product that melts the silicone away like butter: Chorine-free brake cleaner worked very well.

It will melt the silicone inside the fitting so be prepared to re-bed the fixture with something more appropriate. ( I like Sikaflex... 295 UV)

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Old 30-05-2020, 09:52   #9
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Re: Fixing sloppy silicon job

Wire brush, then use a silicone remover. Anything else is futile if you really want it off.
I guess you're sure it's silicone?
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Old 30-05-2020, 10:01   #10

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Re: Fixing sloppy silicon job

Well, if you don't what to rebed you could do what the original owner should have done (aside from rebedding) and tape up first and create a nice neat fillet of sikaflex or your prefered goop.
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Old 30-05-2020, 10:18   #11
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Re: Fixing sloppy silicon job

Lots of good advice here. The gasoline one is new to me. I'll certainly try it.

I avoid using silicone as much as possible and have removed much. Scraping is the only method I found to work. My favorite scraper is a wood chisel. A 3/4 inch one is great. It takes some skill, but at the right angle, it will not scratch.
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Old 30-05-2020, 10:53   #12
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Re: Fixing sloppy silicon job

Originally Posted by eheffa View Post
Chorine-free brake cleaner worked very well.
If this works, I owe you. Fantastic!!
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Old 30-05-2020, 11:29   #13
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Re: Fixing sloppy silicon job

Originally Posted by Jdeuel View Post
If this works, I owe you. Fantastic!!
I used two different Brake Cleaners. (Kleen-Flo and NAPA Brand) They both worked extremely well but the NAPA was much more vaporous and intense on the chemical smell side. (a respirator is recommended if you use the NAPA stuff)

The Kleen-Flo would be my preferred choice as it worked just as well and was much less vaporous.

Neither of them had any visible damaging effect on the gel-coat or stainless steel I was working with. (I have no idea how these agents would affect wood but would expect that they cause no harm to hardwoods.

Good luck.
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Old 30-05-2020, 14:17   #14
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Re: Fixing sloppy silicon job

I had heard vinegar helped break silicone down to help get it scraped off; while working on my water tank's lid sealed with silicone, i found it helpful.
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Old 30-05-2020, 14:39   #15
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Re: Fixing sloppy silicon job

the cheapest effective solvent for silicone is kerosene, or any of its equivalents such as paraffin lamp oil. Best applied by soaking in a bandage like Tear off of cotton rag, wrapping it around the 'joint' and then showing some patience by returning to replenish the soak. I have disassembled an aquarium this way. The silicone turns to jelly.

Dawn washing up liquid or similar is a good solvent for cleaning up the kerosene. Typically the best advise is as with anything...use the least invasive/aggressive solvent possible to get the job done.

while I would agree that a fire risk could still exist. With xylene, gasoline, or white gas stove oil there is the issue with fumes given off with perhaps greater risks of accidental combustion.

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