Advice on freeing stainless steel bolt from aluminium

capetown

capetown

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Yamaha 2.5hp outboard

Due to lack of maintenance (me) the stainless steel tilt bolt is corroded in place.

I've managed to free the locknut end but the recessed head end is solid.

At least it can be tilted now but it's still very stiff.

Because it's painted I can't use heat.

Can I use Plus-Gas? Or will that only work with steel on steel?

Cheers.
 
Don't think Plus-Gas will do any harm - not sure how much good it will do either. I would be tempted to try applying a high-powered soldering iron to the bolt head and getting it quite hot - with luck, the differential expansion will break the bond enough to shift it.
 
Methods of freeing seized parts have varying level of success and usually require patience and perseverance unless you're willing to risk damage. Plus Gas may well work, but you could be putting a few drops on daily for a couple of weeks, try the bolt regularly as the changing tension may help the ol to wick into the thread and break up the corrosion. Once it starts to move, be more generous with the oil and keep moving the bolt in and out to encourage the oil to penetrate. Don't forget that with excess force, the aluminium thread will strip and you'd have to Helicoil the hole to effect a repair.

Rob.
 
capetown said:
Yamaha 2.5hp outboard

Due to lack of maintenance (me) the stainless steel tilt bolt is corroded in place.

I've managed to free the locknut end but the recessed head end is solid.

At least it can be tilted now but it's still very stiff.

Because it's painted I can't use heat.

Can I use Plus-Gas? Or will that only work with steel on steel?

Cheers.
Click to expand...

Plus gas and vinegar will work, but take time. Wrap in cloth and soak it.
 
Heat in the form of boiling water will help and not damage the paint.

Penetrating oil is pretty ineffective against the oxidized ali which is causing the problem. I have used a 50/50 mix of brake fluid and diesel with some success.

But in the end you may need to use some serious heat from a torch.
 
When Oxidised ally doubles in volume from the base metal. So it grips onto stainless fitings very hard. I think you can strip off the oxide with caustic. As others have said penetrating oil such a s plus gas will not hurt - but not help much either. Take the part to a local anodiser (there are plenty around) and ask them to chemically strip the part. The ally oxide causing the problem is the same stuff as the ally oxide they create in the anodising process and most of them will have a stripping tank to repair C**K ups. Take a bottle with you as most of them have a minimum order charge of around £60 if it goes through the books
good luck
Martin
 
Boiling water is most effective at removing salty corroded deposits and gently applies heat Use copious amounts and repeat until it all comes free
 
Rogershaw said:
So would it be possible to make up a paste or solution of caustic soda and use that to free corroded stainless screws in aluminium fittings?
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It would probably strip the surface oxide. I don't think that it would creep into the threads as a paste. Usually the part is immersed in a bath of caustic soda. Once the caustic has done its stuff, the part is washed in water, then dipped in nitric acid to "desmut" or remove the alloy particles. The part is then thoroughly washed again before anodising.
 
claudio said:
It would probably strip the surface oxide.\
Click to expand...

Once the surface oxide was stripped would the caustic soda attack the under lying aluminium.

Soaking in a bath of caustic soda solution would be the best but say on a mast fitting a cup made of play dough/ plaster-seen could keep the solution in contact with the fitting until freed.

Would it be worth a try?
 
Rogershaw said:
Once the surface oxide was stripped would the caustic soda attack the under lying aluminium.

Soaking in a bath of caustic soda solution would be the best but say on a mast fitting a cup made of play dough/ plaster-seen could keep the solution in contact with the fitting until freed.

Would it be worth a try?
Click to expand...

Be careful. the caustic also removes the anodising !

Its definitely worth a try. I would make up some sample mixes at different strengths and experiment first, once you've found out the "characteristics" of the mix then proceed with the real job. It is difficulty specifying the strengths because it depends on what type of aluminium it is, usually alloys.


The caustic will continue to attack the stripped aluminium so you need to be careful and wash off the caustic when its served its purpose.

I would also try painting or coating the samples to see if it protects the anodising, you can always remove the paint afterwards with acetone.

When a part is immersed in a caustic bath it can be aerated to replenish fresh caustic to the surface of the part, also the aeration washes away the oxide so that you can see what's happening.
 
I have used Very Strong Black Tea with mixed results. Just make a cuppa about 8 times normal strength and pour it on. It might need repeated applications over several days. At least it won't damage anything. Good Luck.
 
Before trying all of these nasty chemicals, if you can get the mechanism with the seized bolt off the engine I would recommend boiling it in normal water for a respectable few minutes and trying to undo it with a well fitting socket/ring spanner while still hot, the differential in expansion between the hole and the stud/bolt/bar (more so with aluminium component and steel stud) will normally allow you to get some motion started, and then plenty of release oil and steady, increasing back and forth movements.

If you can't get it off the engine, try steam from something like a wallpaper stripper to get the assembly as hot as possible. Insulate with rags or such like.

Good luck!
 
Last edited:
Update.

Got the engine home today.

One thing I hadn't noticed earlier is that the bolt is painted, so was trying to drift that through as well.

Applied 2 sloshing's of boiling water, then when dry, liberal amounts of "Holts graphited penetrating oil" as I can't find my Plus-Gas.

Still can't drift the bolt out ............but it's FREE, I have a tilting engine.

Many thanks for the replies, I do like the steam idea, I'll try it next time.
 
Try tapping the bolt to break any seal that is locking it in place. If that doesn’t work try a soldering iron for gentle, localised heating without flames licking around the paintwork. You’re only aiming to weaken any join between the corroded parts and perhaps allow penetrating oil to seep between the interfaces.
 
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