Seawater resistant grease

[Rob1978]

Hello,

I am offered two types of grease that I can use for bearings operating in seawater. One has a lithium soap as thickener (Castrol Molub-Alloy 860/460-2), the other one has a calcium soap thickener (Kluberplex BE31-502). Which one is better suitable? Or are there other greases found to be suited for salt environments (splashing with seawater)? Thanks, Robert

 

[MikeHalloran]

The reagents used in some medical equipment are basically synthetic seawater with wetting agents. In a former life, I tried to find an o-ring grease that wouldn't wash away _instantly_ in the stuff. I have no specific experience with the two you mention, but if they are hydrocarbon- based, I wouldn't expect great things of them, except perhaps relative to other similar greases.

The _only_ grease I found that was at all resistant was Dow Corning's highest viscosity silicone vacuum grease, which would be a decent bearing lubricant only when hot.

You might consider a grease optimized for the bearing application, protected from seawater by a v-ring seal and vacuum grease. Of course that requires changing the design so that the v-ring lip has something to ride on, like a thin stainless washer.





Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[EdStainless]

Better than silicone are the Krytox greases. You cna get them with various additives, or just straight.

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Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[shifter]

I would call each of the two manufacturers to get a better feel for the testing each has completed to qualify their product. We've use a product called Aqualube for o-rings and general sealing applications in salt water-proof instruments, but I have not researched bearing greases specifically.

 

[Rob1978]

Thanks a lot for your replies. I am investigating the Dow Corning's lube and DuPont's Krytox for the moment. In our application, the bearings are in use for only 2-3 hours daily and work at low rpm (max 300) and not even continous. That means the main function of the grease is to keep seawater and dirt out. A high viscosity is maybe even better?

 

[EdStainless]

Too high of visc and you will get no lubrication.
It is a tough balancing act. At least Krytox is a good lubricant.

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Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[Rob1978]

We have spoken to a local lubricant expert. His opinion is that the polarity of mineral based oils is better suited for sticking to steel metals. He told us that for seawater applications he never advises synthetic greases because they stick less well to the steel surfaces. He advises us to use a mineral based oil, with a calcium soap as thickener, which gives a better water resistance than lithium thickener. He advises Shell Rhodina Grease EP2 or EP3 (because of low rpm). Kluberplex BE 31-502 was also a good option in his opinion. Maybe this can be helpful information to you as well.

However, we are also experimenting with solid synthetic lubricant of jsh industries, called H2000, and are also still interested in the Krytox.