How to free SS bolt from corroded aluminum fitting

[Cheechako]

Originally Posted by coopec43

Cheechako

Sadly I think you are probably right but I'll keep trying with vinegar for another few days.

I did a bit of a google (dissolve aluminum oxide corrosion) though and came up with this


How do you dissolve aluminum corrosion?

Vinegar does contain acetic acid so in theory yes, vinegar can dissolve aluminum if used in large amounts or for over extended periods of time. In many cases, if you do this, your aluminum ends up with a tarnished finished, possible corrosion and other problems with surface flaking.Jan 24, 2019

Yeah, vinegar probably wont touch it, but acid will. The problem is, the threads are totally sealed with that white corrosion. I doubt anything will get down in there to release it unless it only attacks the corrosion. I'm not sure that heavy white corrosion is predominately alum oxide or not. Aluminum forms oxide on it's surface in air, which is what protects it actually. But that heavy , hard white stuff? Not sure what it is mainly...

[CHM]

Save yourself a lot of time and drill the screw out or carefully cut the head off with a Dremel tool. I’ve not had luck with stainless in aluminum in a 30 year old boat.

[lenseman]

Originally Posted by coopec43

Yes, I've often wondered about WD40 penetrating qualities.

If acetone doesn't penetrate the corrosion I can't think of anything else that would.

Thanks.

WD-40 is nothing more than white spirit. It has as much chance of penetrating as I have of getting drunk on water.


If you actually look up the composition of WD-40 you will find it is white spirit with an SAE 5 oil (sewing machine oil) and a perfume to disguise the smell so you don't know it is white spirit you are buying.


An inch of white spirit, under pressure in an aerosol can for $5 is a win/win situation for the manufacturing company whoo sells the stuff.



https://www.google.co.uk/search?sour...4dUDCAg&uact=5

[nmccubbin]

I agree that drilling out is a last resort
IF you have to, using the left handed (reverse) drill is a good move. A 3/16" drill in a 1/4" bold did the job for me
Heat a good bit above boiling, then applying penetrating oil (of the AFT acetone potion, it sounds good, but is new to me)
Perhaps more acetone than ATF. The evaporating acetone will cool things fast, creating thermal stress on the guk that is holding the threads

Several times
Good luck. Please report on results

To avoid problem in future use Tef-Gel (not one of its look-alikes) We take 15 year old bolts out no problem. We ALWAYS put TefGel on bolts on the boat.

[catalac08]

Originally Posted by tkeithlu

Good point, Northbound.

Somehow stainless steel has a reputation for being a super metal - corrosion free, hard as a rock, etc. It's not. It is gummy. Brass and 1020 ordinary steel machine better, and it is surprisingly easy to shear - far easier than say a Grade 5 bolt.

To my dismay I've sheared a 1/4" ss bolt with my DeWalt 1/4" portable impact wrench.

Be careful! All of a sudden loosening a corroded bolt becomes an extraction job.

When you are up to your ass in alligators, it is hard to remember that the task was draining the swamp. That's not a political comment.

This is the main point-you do not want to shear off the bolt head as centre popping and drilling out the threads has a new set of problems unless you are a good engineer. I have usually found that some heat to the aluminium and then dosing with penetrating oil repeatedly is the way to go. Patience is the virtue here!

[Scrosby]

Pb40 works better than coke with a little heat

[makoman]

Originally Posted by garyfdl

You didn't say how big the bolt is, but given that it is in mast step, I guessing it's rather small.

I suggest using heat, judiciously, focusing on the bolt. Don't heat the aluminum, it melts too easily, let it get it's heat from the bolt. Then I'd bang on the flat of the bolt head with a hammer. If you can't hit the head because of clearance issues, try using a drift pin/punch/another bolt against the stuck bolt and pound on that. Then try and remove it by hand, not with an impact. SS is actually pretty soft and the impact might twist off the bolt-head.

You could also try thermal shocking the pieces. Heat them up the same way, then pour water on them till they cool than try and turn the bolt.

Either way, you are probably going to have to make repeated attempts, before it comes loose.

Good luck!

I would say this is the best answer. Contrary to what some posters are saying, the reason heat works is because it breaks the corrosion, not because metals expand and contract at different rates or with different degrees of heat.

[gamayun]

Heat and AeroKroil. Works every time (so far) as long as you can still get a grip on the bolt. Don't bugger it up!

[lewisa]

I routinely use an impact wrench/driver to free SS fittings in my aluminum mast (e.g. winch attachments). It has never (so far) failed to work.

[Carl-T705]

WD40..... equals Water Dispersant # 40, as defined by the inventor. Want to disperse water use WD40.

That nice "patina" of white blocks any penetrate from passing through. In the end the fasterner is already compromised by the time it corrodes and all the soaking and heating does very little and it will shear off.

[sailah]

Originally Posted by makoman

Contrary to what some posters are saying, the reason heat works is because it breaks the corrosion, not because metals expand and contract at different rates or with different degrees of heat.

uhhhhh, how exactly does the corrosion "break"? From differential thermal expansion.

[Florida John]

WD-40 was not designed to be a lubricant. WD stands for Water Displacement and it was designed to be used on the Atlas missile. It also had some lubricating properties.



I have never had any luck extracting any metal that was frozen tight to aluminum. You'll spend more time trying to get an answer than it's worth. Sorry.


Aluminum, even if it is not galled, expands when it corrodes to the point it almost becomes fused with the bolt. If you want to save the stainless, hack at the aluminum. If you can spare the loss of the fitting, just cut the problem off and start anew.


It you want to play with it, the best penetrant I have found is "Blaster." Spray it on, tap on the fitting, gently until you get angry, spray some more, repeat, and one last spray before you retire. The vibrations from the tapping forms micro cracks in the mated surfaces and helps the penetrant, Check the next morning.



Sorry if I duplicated anything. I read a few posts but not all of them.



Best of luck! John

[SV__Grace]

Having an older, european boat I have lots of experience with stuck screws!

Most recently I had to removed 12 SS screws fused to the aluminum stanchions. Each one was a challenge. Some I got out with penetrating oil and impact driver, and some had to be drilled out.

Cautionary note- I've broken many bits and stripped many screws trying to get them out with a Home Depot cordless Ryobi impact driver. Only try it with a hardened bit that fits tightly in the screw.

I've had better luck with lots of heat and banging on the screw with an old school hand held, knuckle-bruising, non-electric impact driver like this

BTW, the best penetrating oil I've found, recommended by the boatyard guys, is Aero Kroil

There have been times for me when the process of using the above was beyond my patience and it was more efficient and effective to drill it out. If you damage the threads a correctly sized tap will fix that (I've had to invest in SAE and Metric tap and die sets), and a screw extractor makes it easier (be sure it's good quality and hardened as well, I've broken them too!).

[Cisco 37c]

Kroil and heat
Absolutely the best penetrating oil ever! Add enough heat to slightly expand the aluminum, then apply Kroil. When it cools, the kroil will be drawn into the corrosion and turn it into a soupy mess. Then your bolt can be worked out little be little. Don’t get aggressive and shear it off!! It will take multiple applications of kroil and heat, but it WORKS!!

[rcolesny]

Heat, liquid wrench... multiple times, 24hrs interval
and Heat, then ice on the bolt. Just enough to create a seeping space between both metals.