On Tuesday, August 18, 2015 at 4:35:13 PM UTC-7, Jeff Liebermann wrote:
On Tue, 18 Aug 2015 12:01:51 -0700 (PDT), whit3rd
wrote:

On Tuesday, August 18, 2015 at 8:20:56 AM UTC-7, Jeff Liebermann wrote:
On Mon, 17 Aug 2015 15:56:53 -0700 (PDT), wrote:

Battery and ground contact areas eg terminals, clamps, frame connection areas are coated with a thin film of [silicone grease]

suggested that he grease his sheet metal pieces before spot welding
... the grease exploded in the spot welder

Yes, grease is good, but not in the current flow.

There's formulations of grease that don't do that, of course; silicone takes high
temperature, and some greases are intended for electrical conduction in thin
films (they 'break down' at millivolts, and don't even get hot).
http://store.caig.com/s.nl/sc.2/category.185/.f
I've used this grease on rotating connections, at 40A it's just like
a solid wire connection.


Looks like aluminum dust, copper dust, graphite, and/or quartz(???).

Can't be, it's transparent. It's based on a semiconductive component, which is nonlinear:
insulating in bulk, but breaks down (in conductivity, not chemical nature) in
thin films under electrical stress. US Patent #4696832 has more info.

One your rotating joint connection, did you use brushes or a
commutator to make the connection? If so, the path of least
resistance is through these connections, not through the grease.

It was bronze rubbing on a steel element; the grease keeps the steel from oxidizing
while increasing the effective contact area.