How to free SS bolt from corroded aluminum fitting

[JC Reefer]

Originally Posted by Boatyarddog

After 5 years of continuous, dealing with corrosion and Aluminum, SS castings, drilling out fasteners, is now common place.

In a business you rarely have time to slowly let any process take place.

It's just a common procedure, there are some tricks but not that many.

Sharp bits, a bit of heat, thread soak, all of it.

The real damage starts when it gets beaten on, mushrooms the head of the bolt, destroying the casting.

At that point if it's removeable, then take it somewhere they do this for a living.

You'll be better off than in your under equipped garage.

Trust me on that, I do this everyday!

SV Cloud Duster

I mostly agree with you but the OP does not come across as someone who does this as a day to day thing and Boat owners typically DO have time on their side. I personally would not appreciate paying someone who in turn needs to be overly aggressive because they are short on time.

You’re a pro, but others are not. Hearing that they should drill out a screw as a first resort is aggressive, IMO. And for a non pro this advice can be dangerous, IMO. You might have a nice guided drill with fine bits all designed for metal work. But most people will miss something important and screw the aluminum.

As you stated, damage happens when people start beating on a casting. It should be noted that I had never mentioned anything about beating anything. My method should not require beating or smashing or burning anything.

I’m an advocate for using the most gentle means to get the job done. Sometimes that drilling, but not most of the time.

[Boatyarddog]

Originally Posted by JC Reefer

I mostly agree with you but the OP does not come across as someone who does this as a day to day thing and Boat owners typically DO have time on their side. I personally would not appreciate paying someone who in turn needs to be overly aggressive because they are short on time.

You’re a pro, but others are not. Hearing that they should drill out a screw as a first resort is aggressive, IMO. And for a non pro this advice can be dangerous, IMO. You might have a nice guided drill with fine bits all designed for metal work. But most people will miss something important and screw the aluminum.

As you stated, damage happens when people start beating on a casting. It should be noted that I had never mentioned anything about beating anything. My method should not require beating or smashing or burning anything.

I’m an advocate for using the most gentle means to get the job done. Sometimes that drilling, but not most of the time.

Mostly agree with you, I dislike aggressive work.
And if I can complete the job without that, great, as I didn't see the work or size of the fastener, I assume it's 5/16 or larger being a step.
However, the OP didn't provide a picture or size, lenght.
I did ask for that, as yet no more info.
It's pretty straight forward work.
Thanks for your comments.
Hope the OP, is reading.
SV Cloud Duster

[Crusty Joker]

Reverse drill bit. That will heat up metal. Cool with water... and penetrant. Light tapping with slight torque applied. Persistence is a winner. Always. Though, you may try bigger hammer... Use an old toothbrush and try a small amount of vinegar mixed with a small amount of cleaning ammonia but ventilate the area. These mixed together produce a small amount of phosgene (mustard) gas. Usually light oils including diesel mixed with solvents will do the trick... but JetA has no lubrication properties. Sometimes dry ice against the stainless will allow penetrant in. Stubborn ones sometimes require very drastic measures. I have freed up rusted pistons and rings in abandoned engines with dry ice... again ventilate the area as CO2 can displace O2. Give up on occasion and have a beer mate! There are electrolytic processes that will assist this situation but I have never had to resort to them.

[a64pilot]

With aircraft, we drill it out. It’s not hard, I guess it helps if you have drilled a million or so rivets first.
However I prefer cobalt bits over the titanium coated ones, I feel most of them are a marketing scam.
The trick to drilling SS is high pressure and slow speed, do not ever let it smoke or get hot, the reason is you have tempered the SS into a very hard material that is going to be real tough to drill thru, SS really isn’t a hard material, until you work harden it with a hot drill bit

[Crusty Joker]

Sorry that was ammonia and bleach... produces the highly oxidizing agent Phosgene... or Mustard gas... Use very tiny amount to see if it will dissolve the bond produced by the electrolysis. Good luck and keep us posted. We have been where you are now. All of us have resorted to FORCE with varying amounts of success and failure. Good Luck and Encouragement!

[goeasy123]

Center punch and pilot drill the bolt as accurately a you can. Then drill it through with the tapping size drill for the thread diameter. Then tap out the remains. If the thread in the Al is in tack you're done. Otherwise Helicoil it. I usually Helicoil it anyway.


I've done many like this. The Aluminium Oxide melts at 3,762 °F, it expands many time the volume of the Al it comes from an pressure fills the gap between the SS and AL and is insoluble in hydrocarbons. So heat and penetrating fluids are unlikely to work.

[pt49]

Had same problem with screws in alloy on motor bike engines etc... impact and turn at same time... though they were alloy into alloy.
Problem with 2 different metals is the electrolysis is as good as welding.

[Crusty Joker]

Andy Todd speaks true... reminding me. Thanks. What dissolves AlOxide probably also impacts the aluminum... Been a long time. Do you pay your own travel expenses? You could make a business out of this...

[coopec43]

JC Reefer


I'm not ruling any advice IN or OUT at this stage. I do have time on my hands as the pandemic hasn't helped with getting materials.

I do happen to have eight liters of white vinegar on my workshop shelf as I was using it to lower the pH of my lawn. I'll try submerging the mast step in that. If that doesn't work in (say) a week I'll try something else. (I have plenty of ATF on my shelf too)

Thanks everyone for your help

[wsmurdoch]

Originally Posted by JC Reefer

Do not drill it! Drilling is the most work and poses the highest risk.

Other members, please stop telling folks to drill out screws as a first resort, I beg you.

For 3 years I was the guy that disassembled furlers to replace the bearings on a daily basis. Profurl has some special problems as they mix SS and titanium screws into the aluminum hubs.

If your in the US southeast or Caribbean and sent your furler somewhere for repair or bearing replacement then there is a good chance it came to me.

I think we can all agree that furlers are exposed to seawater and are rarely taken apart.

DO NOT DRILL IT OUT. Drilling is a last resort after YOU have screwed up. You risk doing more damage to the relatively soft aluminum. In 3 years the only screws I every drilled out were because the owner (or someone) had attempted the work themselves and broke the screw head off or did some other bone headed error.

An impact wrench will work or it will break the head off. IMO an impact wrench is the second to last choice because it’s all or nothing.

Everyone is talking about penetrants, I like Vinegar. Cheap white vinegar. Take a piece of salt crust and put it in a cup of vinegar. You’ll see a chemical reaction taking place turning the elements in the salt into a gas.

Vinegar won’t easily work it’s way into the thread if your unable to fully submerge the part into a bath of it. You’ll need to use some heat.

Heat, a small amount of heat can be applied without damaging things. I think people get carried away with heat and end up burning things or weakling the metal. Do not bring the screw to a red hot glow, you’ll damage something.

You can heat the metal up enough to boil water (or vinegar) that is sprayed on it and then allow it to cool down. I use a water bottle filled with vinegar. Poke a hole in the cap and you have a squirt bottle.

Do this at least 5 times spraying the screw with vinegar on the cooling cycle using up a 16 ounce bottle of vinegar.
When cooling some of the vinegar will be sucked into the threads as air inside the screw retracts from its expanded state.

If you have done the salt crust in vinegar test like I said then that’s what will be happening in the threads. The now trapped vinegar will turn the salt crust into a gas further loosing the grip.

You can use any penetrant but be carful as some are flammable.

Try tighten the screw slightly then try loosening. After your 5 heat/cool cycles.

This method will eventually work. Threads will be intact, nothing will need repair.

When assembling, thread coating products that others have mentioned are definitely worth it. Lambacoat is one product.

If you end up drilling then congrats for screwing up. But if you must The advice I have seen is correct (slow speed, sharp bit, cutting oil). But you should not need to drill it.

Though its a tough bolt, try and be gentle. It will save you effort and money later.

Let us know how it goes.

Pay attention to this guy. My guess is that he worked for Sailing Service in Miami and has removed far more stainless steel screws from aluminum than you will even see in a lifetime.

Soaking for a few days in white vinegar (5% aetic acid), submerged in a bucket, or with a repeatedly vinegar saturated cloth laying over the white stuff between the bolt and the aluminum, or with a repeatedly saturated cotton string wrapped around the screw head should get it. Just something to keep the fresh vinegar on the white stuff. That failing, after a week escalate to citric acid or lemon juice, then as a last resort 10% hydrochloric acid (diluted muriatic acid). It will be a race, but the acid should dissolve the aluminum oxide before the aluminum metal.

Trying to keep a drill bit centered in a hard metal screw surrounded by soft metal is a fool's errand. The drill will go into the aluminum. The required skill is, well, beyond a normal human's; at least mine.

[a64pilot]

Keeping a bit centered is not hard, especially in a phillips screw, but if not an automatic center punch is your friend, and you start with a small bit and step it up, say 1/8”.
Often times drilling a small hole all the way through a fastener will cause it to release.
I’m not necessarily saying start there, but often with SS in aluminum you will end up there.

Again drilling aircraft rivets out, you have to drill just the rivet you can’t touch the skins or you have to step up to the next size rivet, and many, many are drilled out, it’s a learnable skill. Yes there are steel rivets, some are very hard, ice box rivets for example.

[coopec43]

Originally Posted by Boatyarddog

Mostly agree with you, I dislike aggressive work.
And if I can complete the job without that, great, as I didn't see the work or size of the fastener, I assume it's 5/16 or larger being a step.
However, the OP didn't provide a picture or size, lenght.
I did ask for that, as yet no more info.
It's pretty straight forward work.
Thanks for your comments.
Hope the OP, is reading.
SV Cloud Duster

I have provided a photo but here it is again. Thanks

[Boatyarddog]

Originally Posted by coopec43

I have provided a photo but here it is again. Thanks

Great, if that's the piece, cut the bolts flush, use a drill press to get the pilot hole straight down the center, not really hard on a flat surface like this.
Are you expecting to remove the SS pin the bolt is probably holding as well?
SV Cloud Duster
.

[a64pilot]

Originally Posted by coopec43

I have provided a photo but here it is again. Thanks

I thought it was a mast step, attached to the mast?
Since it’s off, quit screwing with it, take it to a machine shop, they do this stuff all the time and have the equipment.

[coopec43]

I'll try the "soft options first" and if they fail I'll get aggressive. I think one big advantage I have is that it is relatively small and I can submerge it in a bucket of something.



Thanks