Stainless Bolts into Alloy

D

dje67

Well-Known Member
Joined
20 Sep 2007
Messages
360
Location
Largs
Visit site
Just spend hours of my life removing skin, knuckles and nails trying to get the steering quadrant apart. It is made of aluminium/alloy and is held together with stainless bolts tightened into tapped holes in the alloy. Because of a water leak onto the quadrant, the stainless bolts and the steering cable were all completely stuck in the alloy. Eventually managed to get it all apart with much swearing and tears and only broke the steering cable in the process. All in all one of my more successful outcomes.....

Anyway, I've now got to re-assemble the whole thing. It has all been cleaned and all traces of corrosion removed. What should I use on the bolt threads to ensure that I have half a chance of getting it apart in the future? I've got some Duralac, but am worried that it might "lock" the bolt threads. I also thought of just plastering everything in grease. ACF-50 also seemed like a possible candidate.

What's best?
 
Aluminium oxide disolves in water at about 100 degree centigrade. So lots and lots of boiling water and NO WD40, will free a frozen fitting eventually. It took me a day to dismantle a well frozen Aries which is now perfect.

For re-assembly, lots of grease. I use silicon grease. It is expensive but works. Get it from a builders' merchant.
 
dje67 said:
Just spend hours of my life removing skin, knuckles and nails trying to get the steering quadrant apart. It is made of aluminium/alloy and is held together with stainless bolts tightened into tapped holes in the alloy. Because of a water leak onto the quadrant, the stainless bolts and the steering cable were all completely stuck in the alloy. Eventually managed to get it all apart with much swearing and tears and only broke the steering cable in the process. All in all one of my more successful outcomes.....

Anyway, I've now got to re-assemble the whole thing. It has all been cleaned and all traces of corrosion removed. What should I use on the bolt threads to ensure that I have half a chance of getting it apart in the future? I've got some Duralac, but am worried that it might "lock" the bolt threads. I also thought of just plastering everything in grease. ACF-50 also seemed like a possible candidate.

What's best?
Click to expand...

Tef Gel I should think would be a good choice. Not used it personally though

http://www.tefgel.com/contain.php?param=tefgel_infor

Force 4 and other chandlers stock it http://www.force4.co.uk/7168/Harken-Tef-Gel-Anti-Corosion-Paste-28g.html
 
SS into Ali

Yes it is amazing how original manufacturers will happily put SS bolts into Aluminium with no protection at all. Obviously they have no concern a bout the future needs to dismantle the gear.
I reckon grease or duralac is far better than nothing. But occasional dismantling will also help.
good luck olewill
 
I learned my lesson dimantling Japanese motorcycles.

To get seized bolts out, blowlamp heat followed by rapid cooling with water several times over. WD40, and a good quality "surface drive" socket.

Copaslip for reassembly.
 
acf-50 do a grease called "corrosion block", I've used that.

We use araldite for semi permanent underwater fittings, stainless into alloy P brackets, but this needs heat to soften epoxy for removal.
 
nimbusgb said:
Re-assemble with duralac. No it doesn't 'lock' the joint as loctite would.

Keep a roll of paper towel and some thinners nearby. Duralac is messy stuff.:D
Click to expand...

Absolutely correct - have used Duralac for years , even under water on a cat drive leg, and the bolts have always come undone quite easily. Not sure I would rely on it as a locking compound though - if anything it undoes too easily.

Aluminium oxide is insoluble though I'm not sure that is what is produced whjen stainless and ally form a galvanic cell.
 
I think the boiling water thing works more because the aluminium expands more than the stainless when you heat the assembly. In general, heat is a good thing to try if the female part of the assembly is aluminium. Also, if a thread locking compound WAS used in the original assembly, those also tend to soften at between 100 and 120 C, so heat is well worth trying.
 
Tef gel

Yep, that is the best stuff. It is expensive but works a treat. I use it on our windvane steering which has a few stainless to alloy connections. Our quadrant is all bronze so no issue.

If you are yet to reassemble the quadrant you could get bronze helicoils put in. That would solve the prob long term
 
Having read previous posts on the subject - (and there are quite a few!) - the consensus is that you use Duralac when the joint between dissimilar metals is to be permanent, such as a riveted fixture, to prevent electrolytic corrosion causing failure at a later date; however, for screwed joints such as stainless bolts into alloy, PTFE grease such as Tefgel seems to give the best chance of getting things to unscrew at a later date, and is much less messy.
 
elton said:
I learned my lesson dimantling Japanese motorcycles.

To get seized bolts out, blowlamp heat followed by rapid cooling with water several times over. WD40, and a good quality "surface drive" socket.

Copaslip for reassembly.
Click to expand...

+1 but find normal engine oil is better than wd 40 as it is less likely to burn with repeated heatings and gets sucked into the threads as the metal cools
 
dje67 said:
Just spend hours of my life removing skin, knuckles and nails trying to get the steering quadrant apart. It is made of aluminium/alloy and is held together with stainless bolts tightened into tapped holes in the alloy. Because of a water leak onto the quadrant, the stainless bolts and the steering cable were all completely stuck in the alloy. Eventually managed to get it all apart with much swearing and tears and only broke the steering cable in the process. All in all one of my more successful outcomes.....

Anyway, I've now got to re-assemble the whole thing. It has all been cleaned and all traces of corrosion removed. What should I use on the bolt threads to ensure that I have half a chance of getting it apart in the future? I've got some Duralac, but am worried that it might "lock" the bolt threads. I also thought of just plastering everything in grease. ACF-50 also seemed like a possible candidate.

What's best?
Click to expand...
Duralac is better than nothing, but what I've done in similar situations is to open up the thread and use a ss nut with washers on the other side - still use Duralac, but at least you won't have a sheared bolt in the future. Not always possible, though.

In common with VicS I have to express extreme scepticism of the dissolving of hydrated oxides of aluminium in water at any temperature.
If anyone can quote the relevant authority I'd be glad to stand corrected.

In the event of an existing seized fixing, repeated thermal shock will sometimes work - unfortunately weak acids seldom work because access to the oxide jamming the hole is impossible (I've found sulphamic the most effective acid)
 
Thanks for the info. all.

Where the steering cable was joined to the quadrant (a threaded terminal on the s/s rope) it was absolutely solid with oxide. I start the job last wekend and had continuously applied combinations of hot water, plus-gas and ACF-50. When I eventually got the quadrant bracket off the rudder shaft and took it to a workshop, we tried to get the broken stub from the steering cable out. Initially we tried pressing it out, but it wouldn't budge. A set of stilsons on the stub allowed the stub to be unscrewed (even although it wasn't a threaded fit). Loads of absoultely bone-dry white oxide came out with the stub. Thereafter, I was able to simply re-insert the stub and remove it by hand.

The point of this ramble is that I was amazed at how solidly the oxide had managed to grip the stainless stub. Also, I was amazed at how little penetration the various potions had managed to achieve. That was inspite of having repeatedly heated and cooled both the bracket and the stub. The oxide was completely "waterproof" and made an excellent job of locking the thread into the hole!

Anyway, I've hopefully cured the water leak that set-off the whole corrosion process in the first place, so hopefully I'll be in a better place in the future. I'm hoping to replace rudder bearings in a couple of years time and I'll have a very short time-window between getting the boat to the lift-out station and having her in the slings where I can drop the rudder - I now know that it'll come apart! If I'd tried that job this winter, I'd have been in the boaryard slings for a week....!
 
You will always succeed with heat if you can get enough heat into it. But thats the problem. I had some seized M12 stainless spindles in my ally bow roller but even though I got the stainless next to the ally cherry red with a propane torch, I still could not shift them because the ally casting was acting as a huge heat sink and was barely above boiling point
 
I had "white powder disease" between alloy chainplates and the bottlescrew pins. I cautiously used aguafuerte* to dissolve the salty stuff and then quickly rinsed it off once some movement occured.
* I think aguafuerte is hydrochloric acid like brick cleaner.
The white stuff (I think) is a salt rather than an oxide, and probably has some percentage of the original saline which started the corrosion.
I now use liberal grease on rigging pins and Duralac on screwed and rivetted bits.
 
You must log in or register to reply here.

Share this page

Top