Aluminium setscrews

[boden36]

Have any of you used threaded aluminium fasteners?
I want to fasten some hardware to our alloy mast using aluminium M6 setscrews.
The loading will be negligible.
In the past we have used self tapping screws but they have corrosion issues with the mast extrusion.
It seems that aluminium bolts threaded into the mast may be the way to go.
I would be interested to hear any comments from persons who have experience with this application.

Thanks,
Richard.

[Captsteve53]

Richard,

Most all fittings are either Rivets (Aluminium/Stainless OR THE BEST Monel),

Nothing wrong with Stainless steel bolts as long as you use DURALAC in fact any dissimilar fittings should use DURALAC,

Have used this for "to many years to remember"and 10 years later still no corrosion (Would put it on my sandwich if it was edible)-Every boat owner should have at least one tube in the tool box!! Great Stuff and no i dont have any affiliation with Duralac -just an indispensable tool

https://www.fisheriessupply.com/sadd...nting-compound

It's available thru most ship supply stores world wide

Cheers Steve

[sailah]

I've never tried Duralac, but it looks like a great product. I've always used Tef gel for stainless and aluminum mating. Works great and a small jar lasts a long time. Expensive but so are corroded bolts in your mast.

I would think aluminum would corrode as well being that they probably aren't the exact same alloy. Plus a set screw relies on bite to work. Maybe a cup set screw depending on the load. I'd use some type of anti seize though.

[Captsteve53]

Yes have only heard about Tef Gel and never used it (always been happy with Duralac),

It seems to me Tef Gel works on the principle of air exclusion as on the MSD sheet it shows basically no chemicals or "nasty stuff", I do note it states every thing must be very clean and no present corrosion!,

Duralac works the same as a Zinc anode(think of it as a liquid paste zinc anode) it contains Zinc/Barium Chromate ("nasty stuff") I use it for Anti seize applications and gasket applications other than it's formal use as a dissimilar metal joining compound

Cheers Steve

[daletournier]

I always used duralac but couldn't get it recently and purchased Tef Gel. IMHO I prefer duralac, tef gel didnt spread as easily on the threads and its very expensive.

[Terra Nova]

Forget about aluminum screws and use what the pros use.

[boden36]

Thanks all for your input - it seems nobody has first hand experience.
Steve - Duralac sounds good, will order some , thanks.
Terra Nova, your comment is cryptic. Would you like to explain further please?

Regards,
Richard.

[UNCIVILIZED]

Evans Starzinger is a member here, one of the advisory staff come to think of it. And he's used aluminum fasteners before. Commenting about them in another thread about corrosion due to dissimilar metals.

There are various compounds which you can use as a barrier between stainless & aluminum. Some of them better than others. And it's good to know several ways of doing things, along with as much in the ways of pro's & con's of each. That along with a multiplicity of techniques for removing fasteners that get seized up due to this problem.

One other compound is Blue Loctite, & if you use it, it's best to fully coat the threads, instead of just using a drop or two. This after fully cleaning them, mechanically & chemically.

Another is to use helicoil inserts along with something like Duralac or Blue Loctite. Which is what Harken does, & they ship their hardware with said flavor of Loctite.
And there are a couple of other methods, though I've yet to have any coffee for the day as yet, so they're not fresh in my mind. However when you choose a fastener, it's perhaps wise to pick one that has a head which will allow you to apply a lot of torque when (trying to) remove it, in case you do have them seize on you.

If you do a bit of searching using the words Blue Loctite, Duralac, or about removing frozen fasteners you should get plenty of threads to choose from. Most containing good info on your original question, or related ones such as the above info. And of course you could try sending a PM to Evans if you don't find his posted comments on the subject, here on CF, via a search. Where in he ranks the eficacy of the various fastener types & barrier agents.


PS: Captsteve53, for a guy not on their payroll you surely tout a certain substance QUITE loudly. Could you chill a bit on that please, once or thrice per post is plenty. Five times, including links, pictures, & shouting it at 150dB is over the top.

[Captsteve53]

Originally Posted by UNCIVILIZED

Evans Starzinger is a member here, one of the advisory staff come to think of it. And he's used aluminum fasteners before. Commenting about them in another thread about corrosion due to dissimilar metals.

There are various compounds which you can use as a barrier between stainless & aluminum. Some of them better than others. And it's good to know several ways of doing things, along with as much in the ways of pro's & con's of each. That along with a multiplicity of techniques for removing fasteners that get seized up due to this problem.

One other compound is Blue Loctite, & if you use it, it's best to fully coat the threads, instead of just using a drop or two. This after fully cleaning them, mechanically & chemically.

Another is to use helicoil inserts along with something like Duralac or Blue Loctite. Which is what Harken does, & they ship their hardware with said flavor of Loctite.
And there are a couple of other methods, though I've yet to have any coffee for the day as yet, so they're not fresh in my mind. However when you choose a fastener, it's perhaps wise to pick one that has a head which will allow you to apply a lot of torque when (trying to) remove it, in case you do have them seize on you.

If you do a bit of searching using the words Blue Loctite, Duralac, or about removing frozen fasteners you should get plenty of threads to choose from. Most containing good info on your original question, or related ones such as the above info. And of course you could try sending a PM to Evans if you don't find his posted comments on the subject, here on CF, via a search. Where in he ranks the eficacy of the various fastener types & barrier agents.


PS: Captsteve53, for a guy not on their payroll you surely tout a certain substance QUITE loudly. Could you chill a bit on that please, once or thrice per post is plenty. Five times, including links, pictures, & shouting it at 150dB is over the top.

You know when I see so MANY posts since joining Cruiser Forum about dissimilar metal/substances /corroding rivets/Bolts materials and scanning the previous years amounting to the same threads, I was thinking this Forum was about getting the word out as a helping hand, especially as above every one has the same issues!! That substance i shouldn't talk about is a great answer to the majority of galvanic corrosion issue's, way better than thread-lockers in nearly all corrosive mediums,

So be it if thats the consecutive decision,

I am a Marine Surveyor with the IIMS and Lloyd's Maritime(both very well established ethical organizations) and not connected with that substance,

Sorry your forum feels that way about factual posts, Indeed in the future I will refrain from POSTING all together!! (UN BELIEVABLE!)

Steve Warren (MIIMS-Lloyd's Maritime) NZ Cheif Eng 1

[Lake-Effect]

Just curious - I'm only familiar with smaller boats and freshwater. Assuming there's going to be no pressing need to remove the hardware, why not just use aluminum pop-rivets?

[thinwater]

• If the fastener aluminum alloy is different from the base alloy, corrosion will be faster than stainless. I have seen this.
• Aluminum fasteners are much weaker than stainless.
• Aluminum is even more prone to galling that stainless.
• Use any of the products mentioned, or even Lanicote or waterproof grease, and they won't seize.

I have used aluminum bolts and rivets. They aren't better. Aluminum rivets are fine for light sheet metal work, but that is about it. Aluminum bolts are just too soft. As someone posted, just use what the pros use. Stainless or monel. Aluminum just introduces new problems.

If there is severe seizing, it is generally the fault of what is attached creating a potential, not the fastener itself. Aluminum winches, for example, are troublesome.

I've got accelerated aging samples going for a magazine article right now. I had to postpone the article again because none of the products have failed.

[Fence Man]

I like to use rivnuts when rigging a boat. A stainless rivnut with a stainless screw/bolt will solve the dissimilar metals issue with the fastener it's self. For light duty applications, I often use an aluminum rivnut and stainless screw and you could apply your goo of choice to combat corrosion between them. There are some cheaper kits out there for light duty use, and you'll be amazed the places you come up with to use them. I am not in any way affiliated with rivnuts, except in my belief that they are almost as useful as a bottle of beer. But if you need fence, I'm your guy.

Edit: It should be noted that my version of rigging is likely quite different from the sailboat version of rigging. I'm talking about aluminum river boats/airboats.

[sailah]

Originally Posted by Captsteve53

Sorry your forum feels that way about factual posts, Indeed in the future I will refrain from POSTING all together!! (UN BELIEVABLE!)

Steve Warren (MIIMS-Lloyd's Maritime) NZ Cheif Eng 1

Please don't do that. I haven't been here long, and neither have you, but I have found every one of your posts to be exceedingly helpful without the slightest whiff of being salesy or having an attitude like your accuser. Your obvious deep experience in the marine trades gives significant weight to your posts and I appreciate the time it takes to draft responses as you do.

I too have products I have come to adore and you can't help but be enthusiastic and set in your ways when in comes to what has worked for you.

Just my opinion.

[roverhi]

Originally Posted by boden36

In the past we have used self tapping screws but they have corrosion issues with the mast extrusion.

Thanks,
Richard.

Self tapping screws are terrible fasteners to use in aluminum. Not because of the dissimilar metals but the nature of the fasteners. The self tapping screws have very coarse threads which makes for very low gripping power. Put a little torque on the fastener and they move eventually pulling out. I'm just a boat owner but have seen at least 10 instances of the screws pulling out from PO installed self tapper on boats I've owned. Just had to go to oversized machine screws for a padeye that the PO had installed with self tappers on my newest to me boat.

Drilling and tapping for coarse thread machine screws is the way to go. As others have said, use an insulator like TefGel and the fastener won't corrosion weld itself in. Also using an insulator like electrical tape under dissimilar metal fitting or caulk will cut down on corrosion.

Haven't had good luck with aluminum fasteners in other applications. Even though they are nominally the same metal, the alloys differ. Corrosion still happens. The aluminum fasteners are soft and will easily twist the heads off when trying to remove if you have to overcome much corrosion welding.

[Adelie]

Originally Posted by Captsteve53

. . . I was thinking this Forum was about getting the word out as a helping hand, . . .

Sorry your forum feels that way about factual posts, . . .

This forum is not a vehicle for "getting the word out" on any topic though it may serve as such a vehicle from time to time.

This forum is a "place" for anyone interested in cruising to ask questions and post opinions, answers and comments. Thus, on any topic, people with a whole range expertise may weigh in with their opinions and experiences. So anything your write will be among a number of other posts, some with conflicting opinions.

In your professional life your are credentialed, you probably come to a situation recommended by previous clients and/or employers and you have significant defacto power as a surveyor so your recommendations you make tend be deferred to.

Here, all we know about you is what you write. You claim to be Steve Warren (MIIMS-Lloyd's Maritime) NZ Cheif Eng 1. I expect there really is such a person with those qualifications if I were to dig further, and I personally believe that you really are that person. But you might not be. There are plenty of folks that have come thru here claiming to be any number of things they weren't. All we know here is what you write.

There are number of folks posting on this forum that get more than the standard amount of consideration and respect for their posts and opinions. I can think of one person currently on this forum that has name recognition from outside the forum. Everybody else here that gets more than the normal amount of consideration for their posts has been posting here for a long time, writes well, and doesn't tend to get riled up by opposition, even when said opposition is wrong or argumentative or both.

If you want to become a respected source for posts and answers here, keep posting, write well and don't lose your temper very often. All we know here is what you write.

Good luck.

Adelie