Even a simple thing like grease seems to come in countless variations. Does anyone have any recommendations for the best grease to apply to beam strap bolts? (Or, perhaps the question should be, are there any lubricants that should be avoided?)



Thanks

Wouter

Kevin,



I would use the anti-sieze grease for sparkplugs. It can be bought cheap at any autoparts store.



Mike Hill

H20 #791

If you want something to make the bolt go in easier and more importantly come out, I recommend antiseize. They come in three varieties nasty gray grease, dirty black grease and gets everywhere white geese (Teflon) I use the nasty gray (NAPA antiseize) mostly. But when I really need to keep my hands clean I use the gets everywhere white (West Marine). The biggest difference is $5 will buy you a lifetime supply of the nasty gray or dirty black but only a 2 year supply of the white Teflon.

On a related question, are there any recommendations for best substances to prevent galvanic corrosion (dissimilar metals - in this case stainless mast rotator on aluminum spar)?

I used a teflon spacer between the mast rotator of my Dart and the aluminum mast.

If you are talking about the mast post that goes through the front crossbeam, there is not an easy way to do it. There is a lot of load at that point. Nylon and teflon washers flow after a few months and leave things loose.



Once I went to the trouble of installing teflon shrink tube on the post and using ceramic coated washers. It only worked a little better than cleaning and spraying with corrosion inhibiter once a year.

My problem is located at the base of the mast where the SS mast rotator is held to the aluminum spar with a SS bolt.



How about the product, Duralac? I understand that it's not available in the US, but many sailors in the UK seem to swear by it. It was designed for aircraft use. (I read that it is primarily barium chromate.)

Just for grins let's start from the beginning.



The problem is caused by galvanic corrosion. In real simple terms, the stainless steel (SS) and the Aluminum (AL) have different potentials. Whenever you have a electrically conductive path in addition to the contact point, there is a current between the Al and the SS. To support the current the Al corrodes. To stop the corrosion you must stop the current. To stop the current you can break the path (insulate one or both of the materials) or replace the materials with something that will not support galvanic corrosion.



The easiest way is to break the path. You can either stop the metals from touching or prevent a conductive path from forming. The easiest way to do this is to wash the salt away and keep it dry. This is tough if you life near the ocean. There are chemicals that you can spray on that insulate the metals but they wear off easily. You can paint the SS bolt and nut with epoxy and use plastic washers You can put a plastic bushing in the hole in the mast. If you can keep the different metals from touching, you can prevent galvanic corrosion. Don't forget about the inside of your mast. Salt water on the inside of the mast can produce fabulous corrosion



A harder and more expensive solution is to replace the materials with ones that do not support galvanic corrosion. What about a Tornado style Al or carbon rotator with an Al bolt or no bolt at all.





With all of this said, my current solution is to use a bushing and keep the exterior clean. Putting a bushing in the holes and using Duralac would be even better. You would have to wear out your bushing and wear away the Duralac, to have a problem.

One other thing that will help, is to apply a sacrificial anode to the corroding metal (the aluminum part). If you were to rivet a block of magnesium to the aluminum, it will in turn absorb the currents causing corrosion and it will corrode instead of the aluminum. I used to work for a gas company monitoring the sacrificial anodes (bags of magnesium chips) that were electrically connected to all the steel pipe in the ground for the same purpose. They also do the same thing for outboard motors - look at the foot of the drive, you will see a small block of sacrificial magnesium bolted to the motor to prevent the corrosion of the motor and drive.

Given that there isn't much of a load on the mast rotator bolt, I think I'll try inserting bushings and washers.



Thanks for the suggestions.



Cheers,