Painting Silicone Sealant

[Mac of Cygnet]

What paint will stick to silicone sealant?  A water-based paint simply broke into small pieces, and an oil-based undercoat sort of covered it, but very easily peeled off when I tried to paint over it with gloss.

[David Mack]

Is don't think silicone sealants are paintable. Acrylic ones usually are. But check on the label - paintable sealants are marked as such.

[Chewbacka]

28 minutes ago, Mac of Cygnet said:

What paint will stick to silicone sealant?  A water-based paint simply broke into small pieces, and an oil-based undercoat sort of covered it, but very easily peeled off when I tried to paint over it with gloss.

Car plants don’t allow silicones in their paint shops and that even includes some deodorants as NOTHING sticks to silicone.  Even silicone doesn’t stick to silicone.

[WotEver]

Silicone is made from droplets from the devil’s armpits. 

 

 

Edited August 4, 2018 by WotEver

[Dr Bob]

Yep, nowt sticks to silicone. They use them in frying pans you know.

[TheBiscuits]

8 minutes ago, Dr Bob said:

Yep, nowt sticks to silicone. They use them in frying pans you know.

How do they stick the silicone to the pan then?

 

(And I thought that was PTFE anyway.)

[matty40s]

14 minutes ago, Dr Bob said:

Yep, nowt sticks to silicone. They use them in frying pans you know.

We use bacon and eggs. Doesn't stick around for long either. 

[Dr Bob]

6 minutes ago, TheBiscuits said:

How do they stick the silicone to the pan then?

 

(And I thought that was PTFE anyway.)

Silicone.....or some chemical such as polysiloxanes to get technical....stick very well to things. Ever tried Sikoflex?.....but then the surface of the sealant is very inert. Yep PTFE also used as anti stick especially on pans. Even epoxy finds it hard to stick to silicone and epoxy sticks to most things. 

Its not surprising really. Silicones are crosslinked polymers and there are many polymers it is difficult to stick to...for example High density polyethylene. That's a pig to stick things to. I know. I've got a duck made of it and there's nothing stuck to him.

I could discuss surface OH groups that facilitate bonding but this Bombay Saphire is far too nice to spoil.

[Chewbacka]

In your case I know it’s too late, but ONLY use high temp silicone for your stove flue, otherwise don’t allow silicones on your boat.

[TheBiscuits]

https://www.screwfix.com/p/no-nonsense-sealant-remover-100ml/88987

[Mac of Cygnet]

OK, time to confess that this isn't on the boat, but on some new windows at home, where I want to paint round them, including the sealant.  I've got a sort of result with a thick layer of oil-based undercoat, but time will tell....

[MtB]

Danboline bilge paint sticks very nicely to silicone in my experience.

[stegra]

Cut the silicone out, clean the residue with silicone remover and replace with Stixall. That's overpaintable. Bit of a faff though. 

[rusty69]

On 04/08/2018 at 23:16, Dr Bob said:

 I've got a duck made of it and there's nothing stuck to him.

Is that where the saying "water off a ducks back" comes from? 

[jddevel]

Was told by a guy on site once that he had results by washing silicone with "Fairy Liquid" worked. Don`t know the chemistry behind it but worth a try?

[bizzard]

I've found that on externally applied silicone that it if its left alone for a good while to get weathered it loses its surface slipperyness and takes paint fairly well.

Edited August 8, 2018 by bizzard

[Neil Smith]

Try wiping it with panel wipe first, it removes silicones on car paint before re painting.

 

Neil

[Mac of Cygnet]

The Fairy Liquid has certainly got to be worth a try!  Meanwhile I've bridged the silicone with a thick layer of oil-based undercoat, which stayed in place when I carefully applied the gloss.  Masking tape was a mistake, though - just pulled everything straight off.  So a steady(ish) hand was employed after that.

[PeterF]

Tricky Stick (click here) is some sort of priming solvent that helps superglues stick to difficult plastics such as silicone rubber, polyethylene, I have used it successfully with these. No idea if it could be used prior to painting.

[Dr Bob]

1 hour ago, PeterF said:

Tricky Stick (click here) is some sort of priming solvent that helps superglues stick to difficult plastics such as silicone rubber, polyethylene, I have used it successfully with these. No idea if it could be used prior to painting.

The Tricky stick info on that site says its for cyano adhesives ie cyano acrylate ...which is 'superglue' to help it stick to things that you cant normally stick to. Not a clue what it is as there is no msds sheet. It is possible that this only works for superglues so may not work for epoxies, alkyds, urethanes etc. It is likely to work for a coating if it works for an adhesive using the same chemistry but I dont know of anything that sticks to silicone well......or polyethylene for that matter.

[Mac of Cygnet]

I don't see the problem with polyethylene (polythene). I've used polythene repair tape on my polytunnels and it has lasted for years, come rain come shine.