How to free SS bolt from corroded aluminum fitting

[Boatyarddog]

Originally Posted by wsmurdoch

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.

Small screws are quite difficult, these are 3/8" or so bolts, and have a flat surface under, as well is off the boat and can be positioned quite easily in a drill press if needed.
Not fool hardy, you do need the proper tooling, piece of cake for a machinist.
And, perhaps a bit of experience.
SV Cloud Duster

[coopec43]

Originally Posted by a64pilot

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.

Well I have an industrial drill-press and some reverse drills and appropriate taps. But that is thinking too far ahead.

(I'm beginning to wonder if for some reason the previous photo I posted Comment #27 was not updated to the forum)

[coopec43]

I'm interested in what this guy has to say as well.


Re: How to free a steel to Aluminum corrosion bond

You may want to try this, from a truck forum;

I stopped by a friends garage the other day because I wanted to do a crank relearn on my truck. He wanted a case of cheap beer and a pack of smokes to do it, the dealer wanted $150. While I was there I came across article from popular mechanics magazine about a test where they tried different penetrating oils. Here is what the results said

Oil used - Average torque load to loosen

No oil 516 ft/lbs
wd-40 238 ft/lbs
PB Blaster 214 ft/lbs
Liquid Wrench 127 ft/lbs
Kano Kroil 106 ft/lbs
ATF-Acetone mix 53 ft/lbs

The ATF-Acetone mix ranked the best on lab corroded bolts and nuts. They mix it 1:1. I asked the owner of the shop about it. He laughed and said, "Oh yea, we call it Fall Off"
he had it in a atf bottle with a small tip on it. He said the only thing is that you need to make sure that you put a cover on the tip or the acetone will evaporate. I will be trying this soon. Obviously, you need to keep it away from plastic and rubber parts.
Pikey, Mar 5, 2014

Adding a bit of heat will make it penetrate better.


How to free a steel to Aluminum corrosion bond

[sailingchiro]

PB Blaster with squirt several days in a row, then try hammer drill. If still won't break loose, heat with Mapp gas and try hammer drill. By this time, you get mad and break off the head and drill.

On a side note, if you did in fact break and drill, try riv nuts to replace holes that are too big now for a bolt.

I put Riv Nuts in my mast when new. They are cheap and you don't have to thread the holes.

[coopec43]

Originally Posted by coopec43

Well I have an industrial drill-press and some reverse drills and appropriate taps. But that is thinking too far ahead.

(I'm beginning to wonder if for some reason the previous photo I posted Comment #27 was not updated to the forum)

I assume the bolts are just to locate the pin and stop it falling out. Why not drill a slightly bigger hole and tap it?

[coopec43]

I now have one end of the mast step completely covered in vinegar and I intend to leave it until Monday and see if the vinegar did the trick. If it doesn't I'll try the 50:50 Acetone/ATF mix on the other end.


Will report back

[BlueH2Obound]

Originally Posted by coopec43

Well I have an industrial drill-press and some reverse drills and appropriate taps. But that is thinking too far ahead.

(I'm beginning to wonder if for some reason the previous photo I posted Comment #27 was not updated to the forum)

Nope, it was uploaded, there for all to see, some people just don't read the forum before they spout off . . .

[BlueH2Obound]

Originally Posted by sailingchiro

PB Blaster with squirt several days in a row, then try hammer drill. If still won't break loose, heat with Mapp gas and try hammer drill. By this time, you get mad and break off the head and drill.

On a side note, if you did in fact break and drill, try riv nuts to replace holes that are too big now for a bolt.

I put Riv Nuts in my mast when new. They are cheap and you don't have to thread the holes.

Before you do that, and if there's been a mess made of everything, go to a quality welding shop, clean out/oversize the hole, completely fill in the hole with aluminum of the correct alloy, drill original size hole and tap. Done properly you won't be able to tell it was repaired. Reassemble with suitable thread coating. Done.

[coopec43]

Originally Posted by BlueH2Obound

Nope, it was uploaded, there for all to see, some people just don't read the forum before they spout off . . .

Absolutely spot on!

The commenters that get me are the ones that want help locating certain items for the yacht.

"Can anyone tell me the best place to buy marine ply?"

You wonder where they are located so you look up their profile and it is completely blank. After about #16 comments they finally advise they live in Seattle!.

But the ones that really make me wild are the first time posters (Joined CF today) who comment

"I am considering getting into the boat maintenance business, Can anyone tell me what tools I need?"

Incredibly he gets some responses!

[Boatyarddog]

Originally Posted by coopec43

Well I have an industrial drill-press and some reverse drills and appropriate taps. But that is thinking too far ahead.

(I'm beginning to wonder if for some reason the previous photo I posted Comment #27 was not updated to the forum)

How's the project going?
Any results yet, or movement.
SV Cloud Duster

[coopec43]

Originally Posted by Boatyarddog

How's the project going?
Any results yet, or movement.
SV Cloud Duster

I tried to turn the bolt and for a moment there I thought it was turning but on closer inspection I think I was about to screw the head off.

[Cheechako]

I dont think SS into corroded Alum is a valid application for penetrating solution at all. I've removed so many that came out with the aluminum oxide bonded to the SS it's obvious a chemical ain't gonna release it.
You can shock it hard with a big hammer and punch and see if you can break the oxide, or you can carefully start a drill into the fastener, then increase drill size until you have just drilled out nearly all the SS. PITA.

Drilling is very difficult to keep from slipping into the aluminum. Use a drill press and start perfectly on center. My guess is you will never "unscrew" that bolt. Drill or break it off. But if drilling you might want the head on there as a broken bolt is hard to stay on center when you start drilling. Maybe hack saw the bolt off for a clean flat starting surface for the drill. A small machine shop with a milling machine can mill that out. Then you will have to have a Helicoil put in or go to a bigger bolt.

[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

[coopec43]

Some more possibilities?


Search Results

Web results


Dissolving aluminum corrosion - Offshoreonly.com

www.offshoreonly.com

Jun 20, 2017 - No way to hit it from the inside, It's soaking in lemon juice right now, as citric acid is supposed to attack the aluminum oxide... Muriatic acid does a good job of eating oxidation off aluminum.

How to free a steel to Aluminum corrosion bond

forum.woodenboat.com › Building / Repair

Feb 3, 2017 - 35 posts - ‎16 authors
It is a mixture of nitric acid that dissolves carbon steel and leaves aluminium untouched. It took about a week to dissolve four 5/8 bolts and the ...
????? WORTH A TRY?

Fixing Corrosion Between Anodized Aluminum and Steel ...

www.pfonline.com › articles › fixing-corrosion-between-anodized-alu...

Sep 1, 2019 - This aluminum oxide dissolves in some chemicals, notably strong acids and alkaline solutions. When the oxide film is removed, the metal ..

What is Aluminium oxide soluble in?

https://www.researchgate.net/post/Wh...ide_soluble_in

[sailah]

I've removed more corroded bolts than I can remember, I also have a fully stocked machine shop in my barn.

If that were me I'd do the following:

Rosebud the casting until it was approx 150C
Tap the bolt head lightly with short percussion taps
Apply Kroil, wait a day
Attempt to tighten the bolt head slightly
Then try to loosen with an impact driver, not an impact wrench. Just the normal 18V 1/4" drive Makita etc. This won't apply enough torque to break anything but it will shock the corrosion bond.
Depending on how patient I was feeling, I may redo the heat and Kroil.

What I am looking for is any progress, forward or back, of the bolt head. Once you see any movement, you are golden. The trick of trying to tighten is a good one I learned a long time ago. But it's gentle back and forth to break the corrosion bond and that is done with heat (most important) to allow the penetrant to do its magic. Small steps are your friend. I'd keep doing this until it came out or I broke off the head.

If I wasn't feeling patient, I'd clamp the casting to my mill table, indicate the bolt to dial in on center, then:

End mill on the bolt stub to establish a flat.
Center drill
1/4" cobalt left handed using steady downward pressure with lots of cutting fluid. Don't let a drill bit dwell in Stainless or it will work harden as A64 said. Pressure and cutting fluid and a new high quality bit are absolute keys here. If I'm lucky the left handed bit will walk it out but I'm not lucky.
Keep stepping up right handed drill sizes to just below root diameter
Pick out threads with a pick
Retap if threads are ok, if not drill and tap for threaded insert.

Apply antiseize when you reinstall

Before I learned the art of drilling out bolts (and I'm still learning), I just went at it with a corded drill. Well you already know the result. You'll never just stay on axis and the drill bit will wander off into the threads. That's if you haven't already screwed the pooch with a cheap bit and ruined it and work hardened the SS. A true pro can do it free hand with a drill, and I've been lucky. But you are WAY better off with the part clamped down to a table and you can apply heavy quill pressure without fear of it wandering.