Help with dialectric grease and similar products

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zmwworm
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Help with dialectric grease and similar products

Post by zmwworm » Mon Mar 16, 2009 9:56 pm

I need some sort of grease/paste/putty/sealant to seal up the bare metal that is grounding my rollbar lights on my pickup. I have good grounds for all of my lights, and I want it to stay that way. As it is right now, if I were to drive it in the rain I'm sure I'd start seeing orange rust streaks running down from my lights (based on how everything else on this pickup is rusting). So what should I use? Should I use an insulating grease (I believe the prefix is "dialectric")? Or should I use something that conducts, to ensure a good connection? How about something like Liquid Electrical Tape, or maybe vasaline? I need something that will not allow rust even as it is left out in the sun and rain for the next several years. Hopefully it's cheap too. So who knows a thing or two about this stuff?

Bigglez
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Re: Help with dialectric grease and similar products

Post by Bigglez » Mon Mar 16, 2009 10:55 pm

zmwworm wrote:I need some sort of grease/paste/putty/sealant to seal up the bare metal that is grounding my rollbar lights on my pickup.
An RTV compound (also called caulk or silicone rubber)
would be ideal. It will flex with your truck's chassis
and remain watertight. The exterior versions are also
UV resistant. It does not conduct electricity. Try the
local Home Despot or similar stores.

Before applying it make additional ground connections
from either metal to metal (i.e. roll bar to chassis),
or electrical apparatus back to the battery ground. Using
heavy guage multi-strand flexible wiring.

These connections also require protection from moisture.
Adding heatshrink over the soldered joints to solder lugs
will also keep moisture out.

OEM electrical sockets and connectors often include a
'goop' that protects the contacts from water ingress.

RTV will cure yet remain flexible. Some versions emit
acetic acid during curing and should not be used on
electrical contacts (due to corrosion).

zmwworm
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Re: Help with dialectric grease and similar products

Post by zmwworm » Tue Mar 17, 2009 10:39 pm

Bigglez wrote:An RTV compound (also called caulk or silicone rubber)
would be ideal. It will flex with your truck's chassis
and remain watertight. The exterior versions are also
UV resistant. It does not conduct electricity. Try the
local Home Despot or similar stores.
Home Despot - ha ha! Was that really a typo? Anyways, I do have black silicone (oil resistant). I wasn't sure if it would hold up to UV, but it's worth a shot, and if it doesn't then I'll just get some exterior version. The lights have bolts and washers in contact with the metal, I'm thinking that I'll run a ring of black silicone around each bolt hole, then tighten it up, leaving metal contact in the center.
OEM electrical sockets and connectors often include a
'goop' that protects the contacts from water ingress.

RTV will cure yet remain flexible. Some versions emit
acetic acid during curing and should not be used on
electrical contacts (due to corrosion).
Okay, so new question, what 'goop' should I use to help waterproof electrical contacts and connectors? (Think fording a couple feet of water). I would need some sort of grease, would dielectric grease do the trick, or would it wash away easily?

bodgy
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Re: Help with dialectric grease and similar products

Post by bodgy » Wed Mar 18, 2009 12:42 pm

Just a note - vaseline is an insulator - that is not the grease used on battery terminals - guess how I know - 2 batteries later and an upset auto parts shop.


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haklesup
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Re: Help with dialectric grease and similar products

Post by haklesup » Wed Mar 18, 2009 4:02 pm

For the lights grounded to the bar, I would use a brass split washer or galvanized star washer between the lamp and bar. Then once good contact were made, some plain old rustolium spray paint to cover up the metal and keep it from rusting. Just about any grease you use will not last 2 - 3 years in heat, sun, wind and rain, you would need to reapply regularly unless a rubber boot covered it as well. Greese is also a magnet for dust which makes it look sloppy and can accelerate washout. RTV is a good use but it can look sloppy after being wind blown and exposed to sunlight for a long time (and if applied slopply). Wind and rain can also work its way under the leading edge causing it to fail in time.

For sealing connectors, the liquid electrical tape (or its cousin tool dip) is adequate. There are mastic tapes (fusible electrical tape) that you wrap tightly around connections and it sort of flows into the crevices and fuses into a solid waterproof mass. I've seen it hanging near the wire nuts at HD and also in the sprinkler parts section for connecting wires to the valves.

If you use paint or RTV. Clean the area with a degreaser (like Iso Alcohol) before applying to improve adhesion and extend its life as long as possible.

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Bob Scott
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Re: Help with dialectric grease and similar products

Post by Bob Scott » Thu Mar 19, 2009 8:07 am

bodgy wrote:Just a note - vaseline is an insulator - that is not the grease used on battery terminals - guess how I know - 2 batteries later and an upset auto parts shop.
I disgree bodgy. Yes it is an insulator. The purpose of the vaseline is to coat the battery terminals and protect them from corrosion caused by the outgassing of corrosive gas from the battery. You've all seen rust around the sheet metal in the area around the battery.

You don't need a conductive grease. You should to clean the battery terminals of oxidation with a wire brush first if you suspect battery problems or change out the battery.
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Bob Scott
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Re: Help with dialectric grease and similar products

Post by Bob Scott » Thu Mar 19, 2009 8:14 am

zmwworm wrote:I need some sort of grease/paste/putty/sealant to seal up the bare metal that is grounding my rollbar lights on my pickup.
I'd run a proper separate ground wire from the lights to a proper ground terminal. That way you don't need bare steel. Keep the steel painted like it should be.
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Re: Help with dialectric grease and similar products

Post by zmwworm » Thu Mar 19, 2009 10:38 pm

haklesup wrote:For the lights grounded to the bar, I would use a brass split washer or galvanized star washer between the lamp and bar. Then once good contact were made, some plain old rustolium spray paint to cover up the metal and keep it from rusting.
Any specific reason for brass? There's already grade-8 split washers. And what you describe is close to what I did, I just put a bolt and washer in each hole before I painted the roll bar. I'm sure that water will still work its way in though; I've put layer after layer of paint (probably too thick) over less-than-perfect welds and every pockmark still rusted. You just can't get paint around every miniscule corner. What might work is something with a sacrificial anode, like zinc-rich galvanizing primer, but that would be expensive and more work than it's worth. Unless Rustoleum works in a similar way? (I've only used Krylon and Colorplace Rust Control so far).
RTV is a good use but it can look sloppy after being wind blown and exposed to sunlight for a long time (and if applied slopply). Wind and rain can also work its way under the leading edge causing it to fail in time.
I wonder about some household silicone caulking? That stuff lasts many years on exterior windows.
There are mastic tapes (fusible electrical tape) that you wrap tightly around connections and it sort of flows into the crevices and fuses into a solid waterproof mass. I've seen it hanging near the wire nuts at HD and also in the sprinkler parts section for connecting wires to the valves.
If it's cheap I could put it to good use.
If you use paint or RTV. Clean the area with a degreaser (like Iso Alcohol) before applying to improve adhesion and extend its life as long as possible.
I've been using "Silicone and Wax Remover" before I paint anything, which I was told was a better alternative to acetone because it doesn't damage old paint. Is Iso the same way?
I'd run a proper separate ground wire from the lights to a proper ground terminal.
If I recall correctly I was advised against this by Bigglez way back when I was wiring these lights. And even with this extra rust-proofing it has been less work overall, I've avoided drilling extra holes and avoided routing, stripping, soldering, and heat-shrinking 6 extra wires.

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Re: Help with dialectric grease and similar products

Post by Bigglez » Fri Mar 20, 2009 12:38 am

zmwworm wrote:
I'd run a proper separate ground wire from the lights to a proper ground terminal.
If I recall correctly I was advised against this by Bigglez way back when I was wiring these lights. And even with this extra rust-proofing it has been less work overall, I've avoided drilling extra holes and avoided routing, stripping, soldering, and heat-shrinking 6 extra wires.
Hopefully this is less confusing when you consider the science
behind the school-of-hard-knocks advice you getting this round.

Your project has some interesting challenges, the top couple are
to make an electrical system that works well and reliably in
adverse weather and road conditions.

To this end you first need a solid and reliable circuit path, what
we collectively would call a "proper ground terminal".

The easy way to to do this run one or more dedicated wires
back to the battery ground, but doing so is extra work and
materials. A good engineering compromise would be to run
one dedicated heavy guage ground wire, and possibly only
part of the way.

The alternative is to rely upon a hoge-poge of metal to metal
fasteners that in turn may not do a very good job with the
electrical flow, and very likely will deteriorate over time or under
weather and road dirt.

Another factor is that each contact of dissimilar metals will
create a barrier, and lead to lost voltages (i.e. dim lights) or
rapid corrosion of the metals. The rate of decay can be
reduced by selecting better metal pairs as in the earlier
suggestion to use brass and steel together for contacts.
Lastly, you can reduce the cummulative effect of many
such junctions by jumpering across several at a time with a
shorter dedicated ground cable (sometimes called a ground
strap).

Automotive systems are 14V (12V battery on float charge),
so any real work (powerful lighting for example) will draw
heavy currents. Power loss is the square of current, so
errors run up fast! That is why domestic electric power is
sent over long lines at very high voltage.

Future cars will likely operate on 48V DC power busses,
and today the 3rd generation Prius hybrid operates on a
288V battery system.

In "12V systems" even good low ohmic contacts and
connections will cost a lot of electrical power to be
unavailable to heavy loads such as lighting. For example:
A 60W lamp draws 5Amps at 12V, and has a resistance
of just 2.4 ohms when hot. Adding as little as a 1/4 ohm
of contact resistance (metal to metal using ordinary bolts
and washers) would cost 10% of the available power!
The same lamp now runs at 54Watts. In the same case
a ground strap across the weak bolt connection could bring
the losses down to only 2%, or 0.05 ohms, and restore the
lamp to 58.8Watts.

Testing your project is going to be tough. The real test is
whether you have to repair or replace some of your work
a year or so down the road to regain today's performance.

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MrAl
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Re: Help with dialectric grease and similar produc

Post by MrAl » Fri Mar 20, 2009 4:21 am

Hello,


Just a quick note here...

Some brands of silicone rubber in a tube react badly with metal in that it
actually corrodes it after it is applied. A good idea is to test some of the stuff you
buy before slapping it on to something metal, even copper, and especially wiring.
LEDs vs Bulbs, LEDs are winning.

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Re: Help with dialectric grease and similar produc

Post by Bigglez » Fri Mar 20, 2009 8:32 am

MrAl wrote: Just a quick note here...
Some brands of silicone rubber in a tube react badly with metal in that it
actually corrodes it after it is applied. A good idea is to test some of the stuff you
buy before slapping it on to something metal, even copper, and especially wiring.
Bigglez @ Mon Mar 16, 2009 10:55 pm wrote: RTV will cure yet remain flexible. Some versions emit
acetic acid during curing and should not be used on
electrical contacts (due to corrosion).

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