Silicone; Dont use it and why.

[Coastal Cruiser]

Well I am glad that you had success with your silicone. But its been my experience and observation over the last 37 years that silicone is a complete nightmare in almost all cases, therefore requiring my previous posting. So for an added two dollars, that is required for one tube, over time, I like to think that I have saved someone some added grief, either with water problems that have made its way into a core causing aded repair work, or water on a person's head while sleeping on anchor. Cheers

[starcrest]

after having to remove many things from what will be my old boat----I noticed /remembered that 6 years and 4 hurricanes ago (these were direct hits from  francis jean  katrina and wilma)  many of the stantions --and the tabernacle--many deck fittings were infact sealed with silicone. there were no leaks---no drips---no errors----and if  5200 was used there would be no way these things could have been removed.infact the mast head modification utilized 5200 and no way did I bother to try to remove it. the tabernacle was from a 50 foot boat it is over 1 foot square at its base and is/was thru-bolted  thru  the deck and utilized eight 3/8  inch stainless steel bolts or eye bolts and each one was sealed with------you guessed it-----silicone.infact some ports were sealed with a latex silicone- even cheaper---like 1.50 for a tube----no leaks---no drips---no errors----I will say this tho---it did not do to well as a way to lock the nuts in place---they did back off too easily----perhaps they werent tight enuff----but they did not leak whatsoever---and not to be a rebel but to K.I.S.S. I will use it---above the waterline---that much I will agree.

[Sunset]

This has been very interesting. I am going to be installing 5 beckson ports in the next few weeks. They say not to use anything but 100% silicon on their ports. What does I guy do?
Also I have 4 bomar plastic hatchs to install. Would 4200 be safe to use?

Sunset

[Captain Smollett]

My wife's sister just bought a used car on which silicone was used to seal the transimission pan in place.  It did not work too well, and the dealer had to repair it before she took possession.

;D

[starcrest]

I forgot the name of it but threre's another type of silicone that is made to withstand the high underhood temperatures of automobiles.I think its  its called "formagasket: and is used for such things as waterpumps,headgaskets and that sort of thing.I would not use marine seagoing silicone one a car unless its one of those amphibious types.but you have a K.I.S.S. choise.that 5200 stuff costs about 10bux,inwhich case ya may need 10-15 tubes.the acrylic laytex cost me 1.70 per tube,{for above waterline only} so do the math.also before you use anything like that it sure helps to read the directions on the tube to learn how to use it properly.I will swear by it,,,before I swear at it.

[Captain Smollett]

Yeah, there's also permatex  - but those are all used for sealing, not for attaching.  Perhaps my post was not clear.  They had ATTACHED the tranny pan with the stuff, and it DID leak terribly (and smoked).

(I added that anecdote to the discussion just for comic relief).

IIRC, the West Marine 'advisor' gives 'acceptable' uses for various compounds.  I think plain old silicone is quite versatile.  I've found it works well to follow the manufacturers recommendations on when to and when not to use a product.

Just my $0.02.

[AdriftAtSea]

The silicone for high-temperature applications is RTV silicone, which is self-vulcanizing IIRC.  I used to use the stuff when my gearhead twin and I would restore 'Stangs and T-Birds. 

Silicone is a perfectly good sealant when used properly.  Do not use the ones that smell like vinegar, as they cure using acetic acid and can cause some serious corrosion damage if used with any metals.

Silicone is not an adhesive, and that is the mistake most people make.  To use silicone properly, you need to leave a certain thickness of it in between the two surfaces.  After it is fully cured, you can snug up the fasteners, and the pressure against the silicone "gasket" that has now been formed will prove to be quite watertight. 

Yes, silicone can leave behind a residue that can cause serious problems with adhesion for later sealants, paints, lamination, etc.  It isn't all that difficult to remove silicone as there are many cleaning products that will remove it quite readily. 

[s/v Faith]

Unfortunately, there are no good agents for removing silicone oil that wicks into the glass when any silicone based caulk or sealant is used.

  I am sure that the through hulls Eric sealed with silicone did not leak, that does not mean that it was the best thing to use though.  Sadly, what it does mean is that whoever tries to glass over those holes in the future will think so.  The residual silicone oil will weaken the repair. 

  There is a miracle release agent that was designed to undo bonds made with 3M 5200 adhesive.  I am sure that it's tiny molecules can penetrate and release things bonded with silicone also.  I am also sure that it will not remove the silicone oil from the surfaces.

  Windows are the only thing 'Good old Boat' recommended using silicone on in it's article on sealants last year.  This is because the glass/lexan/plexi all expand and contract differently then the fiberglass they are mounted to. 

  Adriftatsea's advice not to use RTV (room temperature vulcanizing) silicone on metal is good advise.  Anyone working with electronics is instructed early on not to use RTV that smells of vinegar because of the accelerated corrosion the acid causes. 

  "Form a gasket" may be fine for your water pump cover, but when it comes to non-engine related boat repair, the smartest thing to do is "Just say no to silicone".

[AdriftAtSea]

Personally, I think I might try the West system approach... but it is a bit extreme... okay...make that very extreme.  The West system, if you've read their literature uses epoxy for most bedded deck hardware.  I'd still use silicone or neoprene for fixed ports though.  There are some good paint surface preparation solvents/washes that do a pretty good job of removing traces of silicone from fiberglass. But silicone is generally not the best of sealants to use in a marine environment.  As a general rule, it should never be used below the waterline... at least according to much of what I've read, including Don Casey's books.

[s/v Faith]

I posted this on the cruisers forum, I realize I had not posted all of this in this thread so here it is.  yes, before you say it I know I am somthing of a silicone bigot...  ;D

.....it was my rant on silicone on the other thread... I am teased about being a bit over expressive on the subject. It is the result of some personal suffering based on silicone and DPO's...

Silicone is an inexpensive sealant that works well as a compression gasket (as has been mentioned in this thread already). I Like silicone for mechanical gaskets, where metal on metal (or metal on plastic) sealing where slightly (very slight) imperfections in surfaces may cause leaks. Something like waterpump (with care not to allow any globs to fall into the cooling stream for fear of causing clogs).

I am sure that the port mfg cited likes silicone, as it does not harm the ports, and allows some flex between the metal port frame, and plastic (plexi) or glass ports.


Having said that, I believe that there ought to be a law banning silicone on docks, in marina's or anywhere within 10 miles of any boat that is not designed to be scrapped before it is 10 years old....

.... Ok, maybe a LITTLE bit harsh... but just a little.  ;D

Why>?

Silicone oil (present in silicone caulk) is made up of VERY small molecules. It bleeds from the caulk into any porous or semiprous medium. While the silicone comes off easily, the oil remains.

Silicone is impervious to water, alcohol, acetone, or any petroleum-based solvent. There are some 'release agents' marketed for silicone, they are expensive and only work to remove the silicone caulk, not the oil. There are 'silicone solvents' marketed, they can wash silicone off the surface but not out of the underlying material (in my experience).

They are also pricey, so you are not going to want to use any real quantity of them.

Surfaces that have had contact with silicone not only will not hold paint, they do not prime well (primer does not bond) nor will epoxy bond to these surfaces.

Auto painters will tell you that silicone wax makes their job difficult. The silicone causes 'fish eye' which they can add an additive that increases the surface tension of the paint, but can promote chipping. THe problems with auto paint are not as serious since sanding can remove the paint which is where the silicone is carried.

Fiberglass, and wood 'wick' silicone oil deep below the surface. Sanding does not remove the oil, and can actually make the problem worse by spreading it around.

In my experience, I have painted, and had the paint lift. I then sanded and washed repeatedly with different products... to no avail.

I even went so far as to conduct 'pull tests' where I epoxied a block of scrap wood to the fiberglass I had tried to clean and prepare..... I was able to knock the block of wood off the epoxied (west, unthickened) surface with a tap from a screw driver handle.....   :'(

After several attempts to address these problems I took to using a sharp chisel to carve out the top 3/16 or so of the contaminated glass, and built up new glass to cover it...... much more work then it should have been.  >:(

Admittedly I am a bit anal about some things, but watching paint chip off of a newly painted surface can really ruin your day. Even taking such extreme steps, I found an area the other day where I did not get it all.. and there is a small crack in the paint where it failed to bond (like you get if you paint over the waxy blush west leaves.)

Everyone does what they think is best for their own boat. I won't even use silicone on the window frames, as I might want to repaint the fiberglass that surrounds it. My hull was laid in 1964, and she is a 'good old boat', maybe that is why I think about the maintenance I do with a longer range view. I plan to keep her for some time, and want whatever I do to her to be good work, or at least something that leaves the boat better then I found it.

OBTW, I think it was last year Good Old Boat did an article on caulks and sealants and they only recommended silicone for windows, and cautioned against getting it on fiberglass and wood.... so it is not just me.  ;)

[CapnK]

From the movie "It's a Wonderful Siliconeless Life!":

"Every time you hear Craig scream, you know that, somehow, somewhere, silicone was applied to a boat."


;D ;D ;D

[AdriftAtSea]

I understand that Santa puts silicone in Craig's stocking when he's on the naughty list.  :D

[s/v Faith]

.....its been my experience and observation over the last 37 years that silicone is a complete nightmare in almost all cases.... for an added two dollars, that is required for one tube....

Yup.   :)

  FWIW,

The price of 3M's sealants have gone up again, and I have been looking around at some alternatives.   

  Here is a great polyurethane sealant that is sold at many home repair stores.

PL Polyurethane Window, Door & Siding Sealant

  It is around $5 a tube.  Works well, and has excellent adhesive (not to strong, not too weak) and will not screw up your boat.

[s/v Faith]

FWIW,

  The sealant I posted above looks like the same stuff Mike talked about in this post earlier in this thread;

Okay, let me stir the mix here. I use a common product that cost me around 4 bucks a tube and can be purchased at most all big box stores.

Its a PL product, called Window, Door, Siding sealant, and works wonders, and yes it can be cut with a razor knife when removal time is required.

Yes its got some adhesion properties, but not to great that you cannot work it out. It flexes, and in most cases, as long as the temperature is moderate, will cure in a day.

The only down side of it, it does take a week or so to properly cure for painting it. You may notice some form of dirt collection on a wide bead, is used, since it will cure but remain sticky a bit. But after the initial cure of it, mineral spirits will wipe most of the tackiness off. But for a good seal, and even improper fits with hatches to curve decks and hulls, it works great. Thats my opinion, of course and like freebies, worth to most exactly what was paid for it,  in most cases. Try it before you place in on a part, if skeptical of it, in you idle time while sitting around the puter, in spare junk we all have in our garages, or cabinets.

If you do not use it all, then just place a flat head, cheap screw driver in the end of it, one of those long ones that you find in the bins that stare you in the face at the checkout, that the tips also break off the second time you use it under load in the ends.  If you have cut the holes small enough, then you do not need anything to save it till your next required fix. If you wait to long and have to cut the tip off to use it, then a sharp razor knife will also remove the stuck leftover off the screwdriver for your next "corking" job.

[CharlieJ]

Just to throw something in here.

We keep our 4200, 5200, etc in the vegetable crisper section of the fridge. In fact, one of the drawers is devoted to boat maintenace stuff like that- sealants, dust masks ( keeps the elastic from going bad) boxes of gloves ( same)

We find that the caulks last for MONTHS that way with no problems.

[s/v Faith]

So I am working on one of the many hundreds of projects around the house that have held me captive since we have returned.  One of ongoing series of repairs involves the containment of a large quantity of water in a hole in my backyard....

  So I have this robotic pool cleaner called a Polaris.  It has refused to do anything but lay on it's side and spin in circles.  So... I take it apart for the third time and pick through the 'water management tubes' and find little bits of clear snot that seem to be blocking the intake to the crawler motor....

  Yes, Silicone rears it's ugly head again! I recall a motorcycle I was working on over 20 years ago when I pulled wrenches in a small motorcycle shop in Louisiana.  A customer had brought in a dirt bike that we had rebuilt the motor on.  I remember spending hours digging bits of sealant out of the cooling passages because of the 'if a little is good, more is better' approach to engine repair.

  So I am thinking... Maybe silicone REALLY is part of a broader conspiracy to bring the western world to it's knees....

[AdriftAtSea]

So Charlie... is there anywhere you consider silicone to be acceptable for use??? :)

[Tim]

So Charlie... is there anywhere you consider silicone to be acceptable for use??? :)

Track slides  ;)

[AdriftAtSea]

I prefer McLube SailKote for those. :)

[CharlieJ]

 ;D and I didn't even comment on it in this thread!! ;D

Laura keeps a spray can of silicone for use when she is sewing on sunbrella or heavy dacron sails- she sprays the seam so the needle passes through easier.

Otherwise it isn't even in our gear  nowhere, no how.

And ALL of our sails go on wooden masts ( on both boats, all three masts) so we have metal track and metal slides. I don't have the problem of them sticking ;)