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[Amps] Use Caution when using Silicon Dielectric Greases

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Subject: [Amps] Use Caution when using Silicon Dielectric Greases
From: "Jim Thomson" <>
Date: Wed, 11 Jul 2018 10:28:30 -0700
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Date: Sat, 7 Jul 2018 12:58:26 -0400
From: "Roger (K8RI)" <>
Subject: Re: [Amps] Use Caution when using Silicon Dielectric Greases

<I didn't find any reference ti Silicon Carbide in Tom's write-up.

There is no carbon involved and unless it's carbon contacts, decomposing 
Silicone dioxide does not form silicon carbide.? The formation of 
Silicon Carbide "normally" requires a high temperature and always the 
presence of carbon.? Typical formation is decomposing HSiCl3 on red hot 
carbon (roughly around 1100C IIRC) The normal result with Silicone 
greases being decomposed by an electric arc is Silicon Dioxide (SiO2) 
which is as abrasive as Silicon Carbide. It just doesn't last quite as 
long.?? Automotive greases (hydrocarbon based) will carbonize in arcs, 
or at high temperatures.

I agree with almost everything Tom said except the way he uses the term, 
Viscosity. Having worked in the Silicone and Silicon industry since 
1961, I have seen Silicones with viscositys ranging from 5 to well over 
6000 Cs.? 5 is used for dry fly treatment for all you fly fishermen. 
6000 is like a very thick taffy
5 is essentially like alcohol except it forms a water repellent coating 
causing the "dry fly" to float.? I don't know what something with a 
viscosity of 6000 would be used for, although there are several types of 
Silicone rubber with some used at fairly high temperatures. At any rate, 
I'd not call a grease, low viscosity. It's maybe a little less resilient 
than what is used in a standard grease gun.

His uses do not go back far enough, as I said earlier, DC4 Compound 
(dielectric grease) was developed to use in the spark plug seals on B17s 
in WWII by Dow Corning. Its use prevented arcing at very high altitudes. 
Other compounds including Silastic RTVs were developed from that.? DC 
did not patent the compound, but rather kept the constituents and 
process proprietary.? This kept them ahead of the game for over 50 years 
until a competitor reverse engineered the compound. Patent life was far 
shorter back then.? Once the product was reverse engineered, silicones 
became a commodity instead of a specialty product which made for a 
drastic reduction in price.

Oh! Depending on what he means by high power, but Flooded UHF connectors 
will work well beyond the legal limit.? OTOH I've been told it is not 
normally a good idea to flood all the connectors in a coax run.

I do have one caveat when using Silicone dielectric grease. Even 
fingerprints with a filim of Silicone grease on them will prevent 
adhesives and epoxies from sticking to the.? Electrical tape will not 
even stick to rubber like cable jackets where those fingerprints exist.

73, Roger (K8RI)

#####   From his site I posted....... on the paragraph entitled....  Switches, 
Movable Contacts, and Relays

     Contact arcs have the ability to alter composition of greases. Silicone 
greases can be converted by arcs to silicone carbide, which is highly abrasive. 
For this reason, silicone grease should be avoided when contacts are "hot 
switched" and have any chance of arcing. 

##  I downloaded the  DC-4  pdf..and also the DC-5  pdf.      Sez  NOT  to use  
DC-4 anywhere near  silicone  rubber, or  the DC-4  will  destroy it asap.  I 
use a LOT of silicone rubber.   Type N and also DINs  have and use  silicone  
rubber O rings etc, so no way do you want to flood connectors  with anything, 
esp  stuff like  DC-4 that  eats  silicone rubber.       DC-4 is white.   DC-5 
is grey. 

##  Im gonna try some of the  conducto lube goop for an experiment,  on the 
roller coil....... since its  ground up pure silver.. in mineral oil.  Supposed 
to be good up to  410 F.     I will report results.  

##  I found better dielectric grease than either  DC-4  or  DC-5.    I will use 
the dielectric grease, a tiny bit, for stuff like the threads on 7-16  DIN  
connectors..and also a tiny bit on the 7-16  Din center pin. 

##  Penetrox and noalox is just ground up zinc  in grease.  Good for yagis and 
al tubing.   Dont use it on roller  coils.  Copper kote is another one I would 
not use.  Its ground up copper  powder in grease.   We used it on bolting 
mating buss bars together at the telco I worked at. 

Jim   VE7RF  

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