Removing RTV Silicone?

Is there a good way to take off this stuff from a pair of flanges? Solvents of some sort maybe? I'm using the Red High Temp kind and it didn't work to well

MEK will probably work. Nasty stuff though.

Razor blade?

Nick

scrape off the bulk of it and clean the rest off with brake cleaner and a rag

MEK? Please elaborate?

Razor blade- slow and surface isn't totally smooth making my life very hard.

I have used a wire wheel with some degree of success in the past.

MEK methyl ethyl ketone?

The present day MEK is a lot tamer than that of yore.
Neutered like TSP, and other decent cleaners.

Good ol' gasoline is the only thing I know that will really dissolve silicone sealer, but it works well.

Be careful!

Razor blade and then apply lacquer thinner. Repeat till clean. The thinner lifts the silicone slightly.

i use a wood chisel for gasket removal/silicone removal. a long handled chisel that is sharp will give good control. 3m makes a bristle disc that works great for removing silicone it chucks up in a holder mounted on a die grinder and turns about 25,000 rpm and will remove even on rough surfaces. i can get you a part number but it will be tomorrow before i can get it.

Metal flanges? Roloc disks and a rotary air tool to spin them.

There is no true solvent for RTV that I know of, but tricholoethlyne , (no longer available), naphtha,(Colman fuel) and I believe gasoline will cause the RTV to swell and loose it’s mechanical integrity.

The last time I had to remove RTV I soaked it in a pan of Colman fuel outdoors, then used wooden scrapers to remove as much as I could and re-soaked in naphtha. MEK didn’t really work, but as a final cleaning I would use MEK with wooden scrapers.

By wooden scrapers I mean things like sharpened orange wood sticks and sharpened hard wood tongue depressors. I didn’t want to scratch up the aluminum parts I was cleaning. You could probably use polyethylene scrapers or Teflon scrapers, most other plastics will be attacked by the naphtha or MEK

ExpTec
DBA
Experimental Technique

Back in the 70's, I used to work in a woofer factory.
Insert bad joke here.
Anyway, we would glue the woofers into speaker boxes with RTV. (Another division made the boxes, and assembled them)
We would get woofers back for rebuilds, and they would have RTV on them.
Periodically, when 100 or so had accumulated, I would clean em up and rebuild them.
The only thing we found that REALLY worked to remove the RTV was HOT Trichlorethelene. Osha about had a fit- this was a big enough place that they came by from time to time, so we had to do it right- a separate room, with its own direct to the outside filtered air system, with a custom built table, 4x8 x 6" deep or so, with 120 degree Trichlor- it was one nasty deal.
I tried to stay out of there, and let the gung ho types, the ones who smoked while using MEK, do that job.
Luckily for my future cancer prospects, I got to do the warranty repairs and custom stuff, and skipped out on spending a lot of time in there.

But it worked- turned the RTV into rubbery slime, which could be wiped right off.

There is a solvent that works but you probably can't buy it. It's pure hexane. I used to use it many years ago to remove the polysulphide sealant from aircraft parts when rebuilding pressurized aircraft and floats for float planes. It's really bad stuff and the maximum exposure limit is only 500 ppm. You can't use it any more without breathing apparatus.

I use a chisel or putty knife for as much as I can followed by 80 grit sand paper.

The sanding makes it easy to see where there is still a film of silicone and is your surface prep for the new gasket and silicone.

Ahhh. I have some of this stuff at home, and the name currently escapes me. It's made specifically for disolving silicone-based stuff. It works quite well. It's not really noxious or anything, and smells a bit like those orange-smelling cleaners. If you soak aluminum in it, it puts a blackened coating on it kind of like soot from a candle. It's not really flammable or vapor harmful.

I got a 1 quart can of the stuff several years ago, and it can't be too hazardous, since it was shipped via air. Name starts with an "R" - I'll repost on it later.

-Mark

Here is a report from Dow Corning. Seems like concentrated sulfuric acid is the only thing listed that will decompose silicone rubber.


Rubber Home > Physical and Chemical Properties > Chemical Resistance Properties > Resistance to Chemical Solvents, Fuels, and Oils

Resistance to Chemical Solvents, Fuels, and Oils

The table below lists typical percent-swell ratings for Silastic® silicone rubber when exposed to various fluids. The data can be best interpreted with the following in mind:

1. General purpose rubber is slightly more resistant to most solvents than low temperature service rubber (those with brittle points of -116 °C).

2. Other factors being the same, high durometer rubber is generally more solvent resistant than low durometer rubber (The harder materials usually contain more filler, which does not swell).

3. When immersed in concentrated solutions of strong oxidizing acids, some rubber materials show a shrink (negative swell). Concentrated solutions of sulphuric acid have a particularly powerful action, and dissolve the silicone rubber.

4. The data given in the table are useful only for comparison of the swell of silicone rubber to that of other elastomers. Swell figures alone may not always give an accurate picture of the deterioration of a rubber. The best way to predict the performance of a silicone rubber is to test it under actual service conditions.

Resistance of Silastic silicone rubber and fluorosilicone rubber to effects of chemicals, solvents, fuels, and oils



Reagent
Silasticsilicone rubber volume change (%)
Silasticfluorosilicone rubber volume change (%)


Acid Solutions (tested 7 days at room temperature)




10% hydrochloric acid
0 to 2
nil


Concentrated hydrochloric acid
0 to 15
10


10% nitric acid
1 to 10
nil


Concentrated nitric acid
-10 to -5
5


10% sulfuric acid
1 to 5
nil


Concentrated sulfuric acid
decomposed
decomposed


Concentrated acetic acid
5 to 18
25


Alkali Solutions (tested 7 days at room temperature)




10% ammonium hydroxide
nil
nil


Concentrated ammonium hydroxide
0 to 7
5


10% sodium hydroxide
0 to 3
nil


50% sodium hydroxide
0 to 9
nil


Solvents and Fuels (tested 7 days at room temperature)




Acetone
15 to 25
180


Carbon tetrachloride
over 150
20


Ethyl alcohol
0 to 20
5


Iso-octane
over 150
20


Xylene
over 150
20


Reference Fuel B
over 150
20


Jet fuel JP-4
over 150
10


Oils (tested 70 hours at 150ºC [302ºF])




ASTM No. 1 oil
5 to 10
nil


ASTM No. 3 oil
35 to 60
5


MIL-0-7808 oil (PQ 8365)
10 to 30
8


Hydraulic fluid MIL-0-5606 (PQ 4226)
over 100
6


Oronite 8200 (silicate ester)
over 150
5


200® fluid, 100 centistokes (silicone fluid)
28 to 35
nil


Skydrol 500 (phosphate ester), 70 hours at 100ºC (212ºF)
10 to 20
25

Seems to me a "swell" rating of "over 150" is consistent with severe attack of the material. That would be in line with the effect of hexane as iso-octane is closely related.

"shrink=negative swell"

Interesting concept, closely related to my checking account.

MEK = Methyl Ethyl Keytone (a chem. solvent relative of acetone)