[TCRA] useful info from QRZ

K9YLI at aol.com K9YLI at aol.com
Sat Oct 24 09:27:35 CDT 2015


    
 
(http://www.eham.net/ehamforum/smf/index.php/topic,105543.msg873797.html#msg873797)  
_RE:  glue ?_ 
(http://www.eham.net/ehamforum/smf/index.php/topic,105543.msg873797.html#msg873797) 
« Reply #12 on: October 06, 2015, 07:07:04  PM »

 
____________________________________
 
_Quote  from: VK2TIL on October 06, 2015, 05:05:57 PM_ 
(http://www.eham.net/ehamforum/smf/index.php/topic,105543.msg873783.html#msg873783) 
Australia may have more-restrictive environmental requirements  than the 
US; there are still a few acid-cure types but the majority are  neutral-cure.

Considering the tiny quantity required to attach a  small meter, it's 
probably not too important for that application but it's  good practice to avoid 
acid-cure.

I don't know the chemistry of  copper -v- acetic acid; does anyone know 
what the product of reaction  is?




Hi,

Warnings about acetic acid cure  silicone seem to go a bit overboard at 
times.  First of all, gluing a  plastic meter to an aluminum board using a 
small amount of this type of  adhesive would have zero risk of harming your 
equipment.  The acetic  acid/water that results from the curing process, will 
quickly dry and  evaporate into the air.

Second, acetic acid is classified as a weak  acid and copper is a fairly 
unreactive metal.  In fact, acetic acid  will not dissolve copper without some 
extra additions to the process  (glacial acetic acid and heat).  If you 
drop a penny into some normal  strength acetic acid, it will turn nice and 
shiny, not because the penny  is dissolving, but because the copper oxides are.  
Note however, if  the "copper" penny is scratched, it will turn black as 
the acid starts  dissolving the zinc that the penny is actually made of!

Of more  concern is solder.  Since even weak acids can dissolve lead and 
tin,  direct application of this adhesive on solder should be  avoided.

Also, even non acetic acid cured silicone will smell like  vinegar, so the 
varieties are not easily determined by your nose.   Look in the ingredients 
for the curing agent used.  I just checked an  assortment at Canadian Tire 
and none that I looked at were acetic acid  cured.

73,



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