Thruster anode and dielectric grease

[max from alaska]

Looking for input on whether it’s a good or bad idea to put dielectric grease where the thruster zinc anode mates to the thruster. Looking to make it easier to remove the anode without compromising its performance as a sacrificial anode.

 

[Automaticman865]

You don’t need the grease just use a sink basin wrench to remove the zinc.
Stuart

 

[BB marine]

I use Quicksilver Anti-Corrosion grease, small dab on the threads and thin layer at the anode to thruster housing matting surface. The only time I had an issue removing the anode was the first time. Since adding dab of grease loosen the Allen head screw and the anode falls off. At the same time I remove the thruster prop, inspect it for cracks, clean the prop shaft splines, dab of grease and reinstall. The prop comes off easy.

 

[Brian B]

I have read not to use a grease on the anode as it prevents the anode from protecting the metal it is supposed to protect. I have also read that the protection is through the anode screw so I don't know what it correct. I don't use any grease on them, I also use the basin wrench to remove them.

 

[BB marine]

I have read not to use a grease on the anode as it prevents the anode from protecting the metal it is supposed to protect. I have also read that the protection is through the anode screw so I don't know what it correct. I don't use any grease on them, I also use the basin wrench to remove them.

I have read this theory for years and have always disagreed for my own applications. The easy way to proof the validity of this is clean the mounting surfaces of the anode and housing or shaft. Install the anode dry with no lubricate. Use a ohm meter. One lead on the anode the other on the component being protected. In this case the anode and the thruster gear housing. You should read continuity no resistance. Now remove the anode and apply a thin layer of marine anti-corrosion grease to the mating surface of the anode and the housing, apply a small amount of grease to the mounting bolt threads. Install and retest for continuity. Through out many years of reading the theory of reduced continuity with grease I have always seen no continuity change. In fact the continuity is maintained when using the grease. The thin layer of grease on the matting surfaces is squeezed out when tightened. The metal surfaces are touching but any voids still have grease to protect those areas from corrosion and the build up of corrosion. The bolt threads also are protected from crevice corrosion.

Before removing anodes that have been used for a season. Retest the anode for connectivity when the is no protection grease. You most likely will see none. You will have crevice corrosion between mating surfaces and in the mounting thread fastener. The removal requires a tool. If anti-corrosion grease is used and there is still an anode left ( if continuity is achieved through out the full season the anode is still working. Once continuity is lost the anode is doing nothing) Test for continuity, then remove the anode and fastener. Allen wrench remove screw then tap the remains of the anode and it will fall off. Look at the thruster housing to anode surface. It should only require a wipe and polish.

The protection is not through the screw it is the anodes contact to the surface it is protecting. The purpose of the screw is to hold the anode in place. Actually it is best to isolate the screw from the anode. The screw is stainless steel so it is more noble than the aluminum alloy anode or zinc. Meaning the anode is protecting the screw more than the housing it is meant to protect. Many anode manufactures recommend insulating the fastening screw from the anode. I believe this to be marginal. ( my opinion) I'm worried more about messing up the housing's fine threads that are used to hold the anode in place.

I have had no issues using Quicksilver marine greases to maintain conductive surfaces between anode and housings. I will point out using grease on the threads of the trim tab anode located on the cavitation plate of outboards and stern drives is not recommended. Use a red sealant loctite on the threads. This will seal the threads from crevice corrosion and not allow the tab to come loose. There are a great deal of forces and vibrations applied to the tab. If grease is used it will fall off. I learned that the hard way many years ago.

This is what works for me based only on my experiences. What ever works for you use. We all have opinions.