stainless steel screws

[torcano]

I am going to replace a simulated wood guage surround that is actually made of aluminum on my boat. Should I use stainless steel screws to attach it to the dash? I understand that the use of dissimilar metals on a boat can cause galvalnic problems. Would aluminun screws be indicated, assuming that they are made?

 

[dingbat]

Re: stainless steel screws

Aluminum or nylon screws would be your best bet. Stainless will cause a white corrision residue sooner or later especially in a place like an electrical panel where an electrical potential is always a possibility

 

[The Great Escape II]

Re: stainless steel screws

I don't think you would have a problem. Your dash is not in the water nor is any electrical connections are made to it. Did you get it in already? The gauges are in a plastic surround. Why not re-use the black washers and screws that were on your old one?

 

[torcano]

Re: stainless steel screws

The existing aluminum guage surround (bipp) on my Chaparral has what appears to be corrosion circles around each screw. That is why I am replacing them. I am not sure what metal the current screws are made of but I would like to avoid this from happening in the future. I suspect that when I remove the current screws the weight will give me a clue as to the metal. My guess is that moisture got trapped behind the aluminum plate and created a situation where electrolysis occured between the aluminum and the disimilar screw metal. If they make aluminum screws, I'll probably go that route.

 

[mlukich]

Re: stainless steel screws

How about a nylon washer between the screw head and the panel?

Just a thought...

Mark

 

[newbster]

Re: stainless steel screws

Take a look at tef-gel. Its made to act as an electrical isolator between dissimilar metals.

 

[torcano]

Re: stainless steel screws

Thanks Newbster. I went to their webpage and the diagram they posted of a stainless steel screw in aluminum with the white corrosion around the screw head looks exactly like my problem. I'll give it a try and hope it works.

 

[redeye1962]

Re: stainless steel screws

How about a nylon washer between the screw head and the panel?

Just a thought...

Mark

I hope the nylon washer will do the trick. It is not easy to find aluminum fasteners. I spoke to a salesman who sells wholesell and he stated just as long as they were separated it should be fine.
I had an aluminum gas tank made and installing it in my aluminum boat was not easy with all the stainless availble fasteners. Let me know what happens.

 

[newbster]

Re: stainless steel screws

FYI, the Tef-Gel also acts to lubricate the thread so you don't gal it out. Any lube will make a big difference there but the Tef-Gel does it all. I use rubber or nylon washers/ gaskets on every dissimilar metal connection with plenty of Tef-Gel to isolate and prevent water from penetrating the connection. I also create gaskets by cutting those flexible cutting boards you buy for a buck. If you have an aluminum boat you might want to look up Galvanic and Crevice corrosion to get a perspective.

Good thread here:

http://www.ifish.net/board/showthread.php?p=1100878

Just stay ahead of the curve and life is much easier.

 

[torcano]

Re: stainless steel screws

I ordered a tube of tef-gel and found aluminum screws at a hardware store near my marina. I plan to use both. I assume there is no harm in "overkill". The aluminum guage surround cost over $400 so that I would prefer to not have to replace it again. Tef-gel sounds like a great suggestion. Thanks
RK

 

[redeye1962]

Re: stainless steel screws

I was under the impression rubber washers that are carbon based will react to the dissimilar metals as well. I went with the nylon based. Can someone confirm this? I wish I was a scientist and understood all of the chemical reactions.

 

[Willyclay]

Re: stainless steel screws

As you might expect, aluminum screws will NOT take much torque. BTDT! FYI, on my 40+ year old Lonestar aluminum boat, the transom brace was thru-bolted with SS machine screws and isolators under the heads. While the rest of the transom skin looked like Swiss cheese from water absorbed by the plywood transom core, there was zero corrosion around the brace screws!
Good luck with your project.

 

[Boatist]

Re: stainless steel screws

My 1980 Crestliner Aluminum Boat has stainless steel screws everywhere,
Including the Bennett Stainless steal Trim tabs I installed in 1981. If you can find corrosion around any screw you got better eyes than me.

My boat does 50 percent of it fishing in salt water but it is a trailer boat so does not spend all year in the water. Also always flush when we pull out of the water.

 

[torcano]

Re: stainless steel screws

The faux wood aluminum surround has a whitish discoloration around the screws. I saw pictures of this and if you go to the Tef-Gel webpage that have pictures that look like my problem. I can't imagine what else would cause this. My boat does stay in salt water 7 month/year. I am replacing the piece and I see no home in trying the aluminun screws with Tef-gel as a backup. It is a light alumuninum piece that screws into the dash so that I don't think I need t worry about being able to put a lot of torque on the scews. Since the boat will be kept in a different marina than the previous owner, perhaps the electrical flow in my marina will be more favorable. I understand that these problems can vary in intensity from marina to marina and even slip to slip.

 

[F_R]

Re: stainless steel screws

Unless you know the alloy of the aluminum screws, they may cause corrosion too. A lot of aluminum contains copper. Bad.

If you really want something corrosion proof, use plastic.

 

[dingbat]

Re: stainless steel screws

The faux wood aluminum surround has a whitish discoloration around the screws. I saw pictures of this and if you go to the Tef-Gel webpage that have pictures that look like my problem. I can't imagine what else would cause this. My boat does stay in salt water 7 month/year. I am replacing the piece and I see no home in trying the aluminun screws with Tef-gel as a backup. It is a light alumuninum piece that screws into the dash so that I don't think I need t worry about being able to put a lot of torque on the scews. Since the boat will be kept in a different marina than the previous owner, perhaps the electrical flow in my marina will be more favorable. I understand that these problems can vary in intensity from marina to marina and even slip to slip.

Well, aluminum will corrode in the presence of chlorides without a precipitator. That is why aluminum is kept to a bare minimum on boat built for use in saltwater. You can use a few of the 5XXX series alloys which are less affected but the fact of the matter is that chlorides and aluminum don?t get along well.


If it was an electrical problem at the marina it would have eaten the zincs off your outdrive long before it ever showed up as corrosion on the screws in a dash.

 

[torcano]

Re: stainless steel screws

The zincs on this boat were totally eaten away. The surveyor commented on this because the boat does have mercathode system. I just bought this boat so I do not know much about the marina where is was kept before. Where can I find 5XXX series alloy screws. I never heard of them. Would a hardware store carry plastic screws?
Thanks