DavidMcMullan
Well-Known Member
Which is better on the bolt threads to allow stainless bolts to be removable from a cast aluminium binnacle after a few years - Duralac or an anti-seize grease? Any better recommendations?
Stainless bolts into Cast Aluminium
- Thread starter DavidMcMullan
- Start date
Iliade
Well-Known Member
pvb
Well-Known Member
I've only had experience with Duralac, which is fairly filthy stuff but seems to work.
Neeves
Well-Known Member
+1, filthy, quite expensive (or it is here), and last forever - except you don't use much and it separates out and is impossible to mix. A small tin would be better than a tube. There must be a reason its not sold in a plastic container??
As you have found the issue with your binnacle you might want to look at your windlass, many, or part of, are aluminium castings with stainless bolts. And they get much more water on them than a binnacle.
Jonathan
William_H
Well-Known Member
I think Duralac is best but any grease you have would be OK. Compared to OEM of outboards who put nothing on SS bolts. However the trick is to remove and regrease every few years to ensure freedom from growing together. olewill
Poignard
Well-Known Member
If I ever bought anything with s/s screws in aluminium, I would dismantle it and Duralac the screws before it got anywhere near the water. Well worth the small effort required.
VicS
Well-Known Member
For a close fitting joint like a screw thread:
Tef-Gel
http://www.aladdinscave.co.uk/tef-gel-anti-corosion-paste.html
Yngmar
Well-Known Member
You don't just need to cover the threads, you need to prevent any hollow area where water can sit without drying out, i.e. under the bolt head or even in the corners. Duralac is well suited for this, as it cures hard and will not be washed out. Tef-Gel remains viscous and can wash out in some conditions or when hit with a pressure washer, not to mention the prices are a joke and it has little advantage over grease. Both are easy to apply but can make a mess, Duralac worse because it's yellow and cures
DavidMcMullan
Well-Known Member
Neeves, I had to remove the top cover plate on the binnacle, held on with 4 M5 bolts. Three of the four sheared off and had to be drilled out. I'll leave the windlass for another day, thanks!!
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JerryHawkins
Well-Known Member
+1 for Tef-Gel. Having experienced ss/ally problems before in the past, but not since using it
jdc
Well-Known Member
+1 for Tef-Gel from me also.
whiteoaks7
Well-Known Member
Helicoils.
rotrax
Well-Known Member
Well, not really.
To avoid galvanic action causing the aluminium to turn to white oxide powder the two disimilar metals need to be isolated from each other.
A helicoil is simply a stainless steel thread in the form of a coil that is inserted into a slightly oversize hole that is precut with a matching thread to the external size of the helicoil. When inserted correctly it is tight and makes a really strong fastening for OE parts that require high strength, or as an easy and reliable repair to a stripped thread.
Unless the helicoil is insulated from the aluminium, if moisture is present the galvanic action will be likely to occur.
Duralac will work, I have no experience of Tef-Gel.
Caught without ANY suitable substance once, I used Vaseline. It was all I had.
I needed to tale the end cap off the boom where I had used it 3 years later and no found no galvanic action and all the fastners came undone OK.
savageseadog
Well-Known Member
Helicoils do improve the holding of stainless screws in alloy. As regards anti corrosive treatments, I've used Duralac and Tef gel and I'm more in favour of Tef gel these days as it doesn't harden and allows easy removal of screws. I'd still use Duralac on monel rivets though.
lw395
Well-Known Member
I use copperslip or the de-luxe silver coloured anti-seize pastes.
Alternatively a threadlock compound.
For military stuff, we'd use passivated SS screws.
Under fittings I use duralac.
Alternatively a threadlock compound.
For military stuff, we'd use passivated SS screws.
Under fittings I use duralac.
whiteoaks7
Well-Known Member
You need to tell all the Navies of the world then - helicoils are used so that the bolt screws into a stainless thread which is the whole point of this discussion. I accept that corrosion will occur between the helicoil and the ally but the bolt contact is still steel/steel. Isn't that why helicoils exist?
savageseadog
Well-Known Member
It's for strength. Aluminium threads will strip relatively easily, Helicoils make the thread larger, plus they are installed at a set depths giving the fixings a defined holding.
rotrax
Well-Known Member
Heli-coils are a very long established thread insert, used for repairing threads and reinforcing threads in soft alloys. They are often used for alloy cylinder heads.
Helicoils will be fine in a severe marine enviroment if insulated from the base metal.
I said galvanic corrosion MAY occur if this was not done.
The OP was clearly concerned about removing the bolts in the future.
Which is why I mentioned insulating the inserts.
How do you know that the navies of the world DONT insulate thread inserts?
I can assure you it is not easy to get a helicoil out once fitted....................
vyv_cox
Well-Known Member
But there is never a straightforward answer. By eliminating potential corrosion between the stainless steel fastener and the aluminium thread with a helicoil, you introduce potential galling between the two stainless components. Isn't metallurgy great!