[Antennas] Penetrox, Noalox, Alumatrox

[Barry L. Ornitz]

Penetrox, Noalox, etc. are materials designed to aid in 
aluminum-to-aluminum electrical connections as an 
antioxidant.  They are not really designed to be primarily 
a lubricating grease or anti-galling agent.  However their 
makeup does contain lubricant which does aid in the 
assembly and disassembly of antennas.

These materials are all made of fine zinc particles 
dispersed in a lubricating binder.  The zinc particles are 
hard and have irregular rough surfaces.  When two pieces of 
aluminum are clamped together with this material in 
between, the zinc particles cut through the surface oxide 
layers on the aluminum and provide better electrical 
contact.  The binder, which is generally a light organic 
material similar to thin petroleum jelly, tends to prevent 
oxygen from getting to the contact points.  Sometimes an 
aluminum soap such as aluminum stearate is added to the 
binder.

Zinc is an excellent material for use here.  Not only is it 
harder than aluminum, a property needed to "bite through" 
the oxide layers, zinc is also compatible with aluminum 
from a galvanic corrosion standpoint.

The Penetrox and Noalox I have used are not what I would 
consider super messy to use.  They are usually a gray, 
somewhat gritty, grease.  They are quite different from the 
black graphite or molybdenum disilicide containing 
automotive greases used to prevent seizing and galling of 
high temperature bolts.  These automotive materials are not 
really suitable for the aluminum-to-aluminum application 
either.  [For high temperature stainless joints, a silver 
containing grease is used to prevent galling.]

While you often see Penetrox suggested for aluminum-to-
copper joints, it no longer provides the proper galvanic 
compatibility here.  It is probably better than nothing but 
copper-to-aluminum joints will always create galvanic 
corrosion problems.

I generally buy Penetrox of Noalox at industrial electrical 
supply stores.  I know Home Depot often carries one or the 
other.

        Dr. Barry L. Ornitz     WA4VZQ     ornitz@tricon.net