Advice on sealing between thimble and class-A

[Slow1]

Where my Class A passes through the wall, on the inside, there is a gap between the outside of the Class A and the metal of the thimble cover (which is basically a thin sheet of metal formed to look like it is something more... sort of lame, but it looks ok I suppose - it does cover up most of the hole and looks substantial from a distance...). Anyway, this gap allows light and some air to flow from the wall into the room.

Last year my sweep 'sealed' it with what I can only assume was perhaps furnace cement - I don't really know what he used. Anyway, it was black when it went on, and looked ok at first. However, it ended up gradually turning white over weeks (weird) and more importantly it hardened. This means it has now cracked over time and with the cleaning the pipe moved a bit and pieces have fallen out and it just looks bad.

I want to pick all of it out from around there and replace it with a better material. I believe that a silicone sealant is the right thing to use - in fact folks here recommended that to me more than a year ago. I had hoped that is what was going to be used when the sweep said no problem I'll take care of it. So now I'm just inclined to take care of it myself. So off to google land I go looking for what to use...

Is this the right thing to use? "Rutland Prod. 76 High Heat Silicone Sealant"? It says it is rated up to 450f continuous and 500f peak. Seems that for normal use it should be well within specs of course - that pipe doesn't hardly get all that warm most of the time - certainly nowhere near 450! But... is there a better product to use and where would I get it?

Thanks.

 

[begreen]

I think a regular good quality silicone sealant should be fine. I'm heading up to the yurt we installed the exterior flue on in a few hours. We used GE Silicone II I think. I'll check how it is holding up.

 

[Slow1]

Forgot to mention that I am wanting something in black (well, blue would be nice but I seriously doubt that exists) so as to match better... but then again maybe that is silly given it is going between the blue thimble and the shiny ClassA pipe eh? Hmmm maybe re-think that requirement here as I type this. A clear may be better....

 

[jeff_t]

High temp RTV from the auto parts store is fine. I just used the red stuff, cause it's in my basement and I don't care what it looks like.

 

[firefighterjake]

I used some high temp fire-resistant silicone in a tube . . . found it at Home Depot.

 

[Slow1]

Thanks guys.

I picked up some "high temp RTV" in clear at a local HW store.

It was a bit of a pain getting that old stuff off - where it was cracked and falling off was ok, but it left chunks of 'rock' on the pipe. On the thimble this wasn't a problem really - I just sanded it off and then re-painted the metal. However with the class-A I didn't dare use anything rough as it would scratch up the surface of course. So I just picked it off the best I could and left some on there - price to pay for old poor work. Figured best to not make it any worse.

Long short - the job is done and it looks much better. Yeah - I should have taken pictures of the process I suppose but I was just trying to get it done, not create a documentary. I think it looks a lot better, wife hardly notices - ha. At least it shouldn't be leaking air around the pipe anymore.