Dielectric grease or Heat shrink tubing

[floatsome]

I've been reading and re-reading that most interesting article in July Practical Sailor. It arrived just after I installed our new audio system, but fortunately it confirmed what I did.

They set up tests in worst conditions, to force failure over shorter time frame.

The last sentence of the article notes their findings and conclusions are provisional until testing is complete. They wroet that they cannot comment on a best-value product for a corrosion prevention coating until the testing is done.

Regarding the insulating properties of corrosion protection coatings like dielectric grease, they do not comment more precisely on the insulating effect it might have on connections when applied internally, simply saying there is "potential for trouble". They recommended:
1. No, on wires prior to crimping and inside push-on connectors prior to connecting, but yes after.
2. Yes, on bolts prior to connecting, because the grease will be squeezed out of the connection to allow electrical conduction and then the grease will protect remaining metal surfaces.

They say to apply corrosion protection to the connection after crimping and before heat-shrink tubing. They recommend against putting corrosion protection on the wire prior to crimping I think not necessarily because it might cause increased electrical resistance, since crimping will simply push it out anyway. The nagging thought in my mind is that by applying it prior to crimping, then the crimping action will squeeze it out to eliminate resistance effect, and then the residual might coat non-crimped surfaces more effectively than I could do by coating after crimping. Perhaps this is just splitting hairs, however, and on balance it is simply best not to apply corrosion protection prior to crimping, which was their pragmatic conclusion.

In the figure showing results comparing 3 wire types and 2 corrosion preventive products, the caption reads "Heat-shrink insulator did not appear to provide any significant advantage" (in their worst-case test situation). In the text, they wrote that heat-shrink insulation adds reliability and prevents salt from migrating up the wire, but they did not see added benefit in dry conditions. I like the added mechanical support it can provide to a connection for any environment. I don't think they mentioned glue vs non-glue heat-shrink tubing, but glue seems to make sense to me, if it lasts and if it is not defeated by corrosion protection products applied over the crimp.

The article notes that corrosion protection coatings do not last forever, and the heat-shrink tubing does not completely protect against creeping corrosion, but on balance it seems better to use both on boats.

The article notes that corrosion protection products can burn, so no need to apply globs and invite trouble.

So, my practice on our boat is:

1. Use tinned marine wire.
2. Crimp connections wherever possible.
3a. Apply thin coat corrosion protection after crimping, and after joining low-pressure push-on connections in electronics.
3b. Apply to inside surfaces on bolted connections prior to connecting and tightening.
4. Apply heat-shrink tubing for both corrosion protection and mechanical support.
5. Visually check connections periodically and revise corrosion protection, especially in water-exposed areas.

Have I got all that right so far? I look forward to seeing the final Practical Sailor results next year.

[Maine Sail]

Originally Posted by floatsome

So, my practice on our boat is:


4. Apply heat-shrink tubing for both corrosion protection and mechanical support.


Have I got all that right so far? I look forward to seeing the final Practical Sailor results next year.

IMHO an easier approach is to use factory made adhesive lined heat shrink crimps. I pay .27 - .38 each for them and the labor savings alone is HUGE. This is the same material used in wells that can be over 200 feet deep and those connections stay 100% dry for 20+ years.

Doing it the way you describe leaves a lot of questions. Are you using non-insulated crimp terminals? If so you must use the proper crimp tool as one designed for insulated crimps won't work. If you are crimping insulated terminals and slide the heat shrink over the insulation it rarely will shrink enough to seal properly around the ring or fork end of the terminal.

Also it is very tough to get solid "mechanical support" when you've used a corrosion protector under the heat shrink as it will slip and not grip the jacket of the wire.

This blue butt connector alone held this anchor with no crimping because the adhesive sealant was able to bond to the wires jacket.




Pre-made terminals are far more consistent. Most every good marine electrician I know up here uses only pre-made adhesive lined heat shrink crimps as the labor savings alone pays for itself very quickly..

There are many on-line vendors selling good quality heat shrink crimps at reasonable prices such as Sailors Solutions.

PS The author of that article is a forum member here who may chime in. It was also stated that for wet applications heat shrink butts, same concept as the adhesive lined butts used in wells, are the only way to go. I much prefer heat shrink on all connection and then simply coating the exposed ring with a product like nooxid or noalox using a flux brush..

I generally try and not use push on connectors but it often can't be avoided so coating/filling them is a very god practice..