Stainless steel screws in aluminium.

[Allan]

I have some aluminium stantion bases which have stainless steel bolts corroded into them. The holes are not threaded so I'm wondering if I can attack the corrosion with chemistry before I try to free the bolts. They are off the boat.
Does anyone have any recommendations of what liquid to try?
Allan

 

[coopec]

Have you checked out the videos?

 

[Allan]

I'm in the yard at present with not enough signal. As I have other jobs to do I thought I would ask the specific question about what chemistry may soften the corrosion?
Allan

 

[rotrax]

Heat usually works for me, with a flame.

 

[Tranona]

Boiling water is a good start. Penetrating oil overnight might help. Then heat and/or pressure if it is possible. Watched a video the other day of removing a seized suspension pivot bolt in a rear hub carrier of a Lotus - took 5 tonnes to shift it.

 

[Martin_J]

Boiling water and time...

Sounds like the prop I had stuck on a small outboard once. Numerous kettle fulls of water every evening for a week..

About to give up and use even more force then it just started to move one evening and wasn't too bad to be honest..

Patience was key to not breaking anything.

 

[Martin_J]

The prop was aluminium and the shaft was stainless so a rather similar situation.

 

[Fr J Hackett]

It will be aluminium oxide that has formed in the joint and swollen such that the bolt is effectively gripped by the stanchion. As been said it's a question of softening the powder and getting something like water into the joint. Boiling water has the benefit of the heat expanding the stanchion base and slightly opening the joint allowing water to penetrate, a mix of diesel and brake fluid is an excellent penetrating agent and will probably work as well, plain heat and applying some force either turning or simply hitting the bolt may help. I would try all in the order I have described.

 

[Allan]

Many thanks for all the replies. I have three in all, one scrap and two good ones. I'm going to put the scrap one in boiling vinegar tonight and one of the others in boiling water and we'll see what happens.
Allan

 

[FWB]

ACF50
https://www.sportsbikeshop.co.uk/motorcycle_parts/content_prod/339234

 

[vyv_cox]

Hydrochloric acid will clear it in seconds. Wash well afterwards

 

[Allan]

Hydrochloric acid will clear it in seconds. Wash well afterwards

I decided to try vinegar first. After about an hour in boiling vinegar I managed to remove three out of four bolts. I have one left which I've decided to leave in the vinegar overnight. I'll possibly try it on the press tomorrow.
Allan

 

[vyv_cox]

This photograph shows an aluminium masthead antenna bracket with an antenna base firmly 'welded' to it by typical carbonate seawater deposits. It can be seen that I have removed the nut and locking washer but the fitting was immovable without the risk of destruction. I dripped a small volume of hydrochloric acid onto the white deposit, it fizzed nicely and within a minute the base could be pushed out.

Hydrochloric attacks pure aluminium but most alloys with additions of other metals are fairly resistant, Attack is not severe or rapid and prompt washing in water will mostly prevent any visible deterioration.

 

[Ammonite]

Hydrochloric acid will clear it in seconds. Wash well afterwards

Just regular brick cleaner or anything more specific?

 

[vyv_cox]

Just regular brick cleaner or anything more specific?

Any dilute stuff will do. Brick acid seems to be about the same strength as the bottles sold in European supermarkets, about 6% w/w.