Corrosion Proofing Under Vehicle Electrical Joints.

[George7941]

Here in the salt belt one has to take extra measures to keep corrosion out of electrical joints. I use adhesive lined heat shrink to keep moisture and resulting corrosion out and it works well. But heat shrink has to be applied before soldering or crimping two wires together. What can you apply after the joint has already been made?

Liquid Tape - I am going to buy a bottle and try it out. https://www.delcity.net/store/Liquid-Tape/p_790066.h_790067
Hot Melt Fusion Tape. Never tried it. https://www.delcity.net/store/Adhesive-Fusion-Tape/p_818697.h_818698
Cold Shrink Tape aka Amalgamating Tape. I use it but it does not waterproof well. My primary use for it is over the usual vinyl insulating tape to keep the end from unravelling. https://www.delcity.net/store/Cold-Shrink-Tape/p_77309.h_78132

Last week I was working under a truck and saw a joint where the box upfitter, for powering box clearance lights, had soldered on to a wire in a OEM harness and had taped it up with what looked like black vinyl insulation tape. After mentally cursing him and anticipating lots of corrosion under the tape, I took the tape off and was truly astonished to find a pristine soldered joint underneath, as clean as it was on the day the joint was made. There was a very light grey paste which had protected this joint for fifteen years in very harsh conditions. This paste was quite thin in consistency, like mayonaisse. The tape might have had this paste lining or the paste might have been applied first and the tape wrapped over the paste. I should have taken a pic but I didn't. What was this paste?

 

[Dave9]

You don't put any paste under vinyl electrical tape, the odds are very high that will make it not adhere well and unwrap later. I'd guess you just saw the remains of rosin solder flux which is mildly hygroscopic so absorbs moisture, along with being slightly acidic will leach out metal from the solder joint to account for the color.

I don't see the issue otherwise, if the joint isn't corroding then leave it alone. If it is, redo it and use the heat shrink tubing, or some prefer shrink sealing crimps, though *fresh* (or else it may not adhere well) self fusing silicone tape would do what you're looking for, if the vehicle can sit several hours for it to bond well to itself, but it is best for 1:1 wires not a tap like you described where there are two wires coming out either end so there is a slight gap between them. In that case, adhesive lined heatshrink is your best bet, OR just don't let people touch the vehicle if they're going to rodeo cowboy this with taps under the vehicle instead of taking the wire run further to where the junction is up out of road splash.

 

[George7941]

It was not flux, there was way too much of it, it had been applied after the joint was soldered.
As for not letting people touch it, not possible without taking extra ordinary measures. When a new truck is ordered and it comes in, it gets sent to the box manufacturer and they fit the box on and make the electrical connections at their shop.

 

[meep]

Gray paste sounds like anti-oxidant grease. Pretty smart, actually. It’s available at Home Depot in the electrical section. The clear dielectric grease woould work too. Whomever did that solder joint went the extra mile, to be sure.

we had a 1977 toyota corona. Every single electrical connector was filled from the factory with clear dielectric grease. You don’t see that anymore.

 

[George7941]

Adding to Liquid Tape, Cold Shrink Tape and Hot Fusion Tape, what about 3M Scotchfil? Any one with experience using it?

3M(TM) Scotchfil(TM) Electrical Insulation Putty : Amazon.ca: Tools & Home Improvement

3M(TM) Scotchfil(TM) Electrical Insulation Putty : Amazon.ca: Tools & Home Improvement

www.amazon.ca

 

[JHZR2]

Grey paste? Maybe something like noalo, the paste used in aluminum electrical connections?

 

[George7941]

No, it was not NoAlox. I have Ox-Gard, which looks the same as NoAlox and the stuff on the truck was much lighter in color, almost milky white, and runny. Clear dielectric grease and NoAlox are thicker.
I still cannot wrap my head around how well this stuff protected the joint. You have to live in the rust belt to appreciate how difficult is it to keep corrosion at bay. As for applying any soft compound, like grease, to provide protection - it does for maybe a year or two and then it actually promotes corrosion when the grease becomes saturated with salt and moisture. The grease has to be protected against contamination to do its job.