Need help separating corroded aluminum parts

[Bill Seal]

Aluminum oxide is what grind stones, sand paper, and anodizing are made out of. Maybe unobtanium acid, or the stuff from the movie Alien could dissolve it, but not much else.

[Capt Montana]

To prep aluminum in aviation for paint, we use phosphoric acid, known in the industry as etch or brightner. It is a very mild mixture and we usually thin it that mixture again with water to about 10 to 1. I have never used this on corroded parts but on corroded skin it will turn frosty and will dissolve the corrosion even down in the pitted areas. One must be careful on high strength steel parts with any acid or one might cause hydrogen imbrittlement.

[CdS2 Roland]

Hi,
I would cut the tube 2 inches over the base. Then make 2 vertical cuts from inside...and use hammer

Good luck

[Bill Seal]

Another thought, cut them a few inches long, drop dry ice inside and (CAREFULLLY) heat the outside with a propane torch.
I got a stanchion out of it's base with PB Blaster, but that was SS

[Exctyengr]

I think perhaps the condition that you are dealing with is "galling". Aluminum is particularly susceptible to that condition. It usually occurs between similar metals like aluminum that forms a protective oxide barrier that are introduced together by a friction fit - quite often in screws and similar friction inducing connections. Basically the mating surfaces become welded together. (Note: We see this often in aircraft). In my experience, I have not found any effective means of separating galled components. As previous posters have suggested, a destructive approach using hack saw and chisel might work. I doubt that twisting will work as the friction will simply increase the galling. I don't know how you would dissolve the bond using acids (I don't use acids on aircraft) but it might work.
Bottom line, try anything but be prepared to replace the fittings. DO NOT USE TWO ALUMINUM FIXTURES IN ANY KIND OF FRICTION INDUCING ENVIRONMENT. Good luck and keep us posted.

[jimbunyard]

If the legs and bases are tapered as common sense would dictate, then rig up your bottle jack press, put as much pressure as your dare on it, and, starting at the top, strike blows somewhere between taps and medium heavy, with a medium-size steel hammer, around the perimeter of the frozen joint. If you have even pressure the 'bond' should yield relatively quickly, if you're lucky with a satisfying pop. If the pressure is canted to one side, maybe not so much...

[Tingum]

Now you know why they make Never Sieze. Messy stuff but it works!

[Montanan]

Originally Posted by skipmac

From personal experience I doubt anything less than C-4 will be ineffective.

The oxide formation joining the two separate pieces makes for a tremendously solid bond, perhaps even stronger than the base metals underlying the surface.
Aluminum oxide being much more chemically stable then the base metals I don't see any manner of dissolution or major effective lubrication because the penetrating oil will only get between not chemically bonded metals, that is to say the gaps.

I would go with applying high torque, remove the leg from the table and try to twist the post from the taper hole. Recommend renting a chain torque wrench, manual with a cheater / impact bar, or hydraulic.

Being that dynamite and ANFO are at least for me much more readily attainable and cheaper than C-4, and are materials I keep for use at my hobby underground gold mine, I too might ultimately go with blasting, but the collateral damage could [read, will] be quite significant, but all so very spectacular. Be sure to raise the Bravo Signal Flag to warn other mariners and so as to be compliant with COLREGs. Bravo means: "I am taking in or discharging or carrying dangerous goods." (Originally used by the Royal Navy specifically for military explosives.) And do be kind enough to yell over your hailer and via a VHF transmission a Pan Pan: "Fire in the hole." Those informative actions should aid in assuring that others in the marina are keeping their proper social distancing and also keep the anchorage less crowded. Especially if repeat and / or larger blastings are necessary to get the job done.

Be prepared to gather the fish that will float to the surface near your vessel after the discharge, Fish Fry Time.

That reminds me I'll need to refresh my stockpile before the 4th of July celebration so as to craft some noise makers. Two to four inch diameter PVC pipes cut to a two or three foot lengths, filled and capped at both ends makes for some thundering rumbles. Especially when set off in fuse delayed sequencings.

Given that there are stay at home orders, one may need to have the dynamite, blasting caps, fuse cord and ANFO delivered instead of going to the store to purchase and pickup. The most recent time, I found it easier to make a telephone order and have it delivered to our property instead of driving an hour to and fro the supplier like we used to do. Be sure to give the delivery person a nice tip. The last time they took a credit card for payment, with signature on receipt, but I suppose cash or a debit card transaction would be acceptable. Advisory note: Don't place your luggage near the ANFO. One time, my father in law drove me to the airport so I could catch an early morning flight and I put my luggage in the back of his pickup truck which truck we had used to recently transport bags of ANFO and a box of dynamite and a roll of fuse cord. I told them that if they were to swab my luggage and coat that their equipment should detect the chemicals, and sure enough when they did, it tested positive and I had given them permission to open and inspect my luggage before they tested. Sure enough, and reassuringly, the chemical detection sensor at the Transportation Safety Administration checkpoint picked up the traces of explosive residue on my carry-on suitcase and briefcase requiring them to search the luggage before being permitted to continue towards the departure gate. I figured it would be easier to notify them ahead of their detection so as to mitigate any adverse response and uncertainty. Now when I go through that same TSA point and some of the same crew are again present they smile and ask if I have explosives that they should look for which typically makes the other passengers nearby a bit wondering and at unease. Being on a first name and facial recognition basis with TSA allows me to go through their rapid line. Apparently, I am now considered to be of low risk profile. Go figure.

[jmschmidt]

No matter how you try, or what you use, you will most likely damage both. So plan on new base plates as well as new table legs. You could make new base plates yourself or hire someone to do it. It shouldn't rocket science. Why try to use old corroded ones anyway?

[bensolomon]

What about old fashioned naval jelly?

[kenbo]

Originally Posted by CdS2 Roland

Hi,
I would cut the tube 2 inches over the base. Then make 2 vertical cuts from inside...and use hammer

Good luck

This is by far the surest method but you really should use a capeing chisel and four cuts to separate the tube from the base.

[doog]

Aluminum corrodes to Aluminum oxide which is (About, I recall..) 8 parts O2 to one part Aluminum and its explosive. Huge volume of oxide is generated and in a closed assembly its not merciful. I had aluminum stanchion bases with SS through bolts and one or two bolts were successfully removed three years after original assembly, the rest sheared off without a chance to get them out.

I had new bases made rather than drill out and re tap them. By far easier..That's the deal, sorry to say and no amount of tech or research will find this to not be the case.

Best of luck..

[keyway]

I use a die grinder for all sorts of projects. A 1/4 inch spindle in a rotary tool with the abrasive rolls twisted on will quickly remove the cut off legs from inside the bases without a lot of damage. A variable speed tool is best.

[Madehn]

+1 on the heat the collar and fill the leg with ice- but you need to pull them off the boat to do it- you are going to want to put the heat to them with a torch not a heatgun then dump some ice down the tube-- stay out of the way as it may turn into a steam gun for a moment there-- you want a large thermal shock if possible- I would bite the bullet and take the fittings off the deck-- if you do that you may be able to access the bottom of the legs from the underside and drive them out with a sledge-- if you get them off the boat hitting them with an air hammer might help to jar them loose but my bet is on the sledge-- in the long run you are better to remove them from the boat - simple job to remount them afterwards-- I think the key to this is going to be brute force not chemical ---good luck

[roverhi]

If you can't use a torch because of location, adjacent materials you can do the following to apply heat.

Jumper cable trick.
Hook jumper cables up to the battery as you normally would. On the other end put a bolt (1/4" x 2" bolt works fine) in the postive lead clamp of the jumper cable. Clamp the negative lead as close to the offending bolt as possible. Touch the bolt in the positive lead clamp to the head of the fastener. You set up what is essentially an arc welder. Will heat the fastener to a cherry red if left in contact long enough. It also gets the fastener way hotter than you can with a MAPP torch. It works really well as it only heat up the area of the fastener and not burning up the surrounding country side like you do with a torch. It is really the only way to get serious heat to a fastener if there is painted surfaces or plastics close by. Quench the heated fastener with penetrating oil. Try to remove the fastener with an impact driver, either manual or power. Repeat the process till you break the fastener loose. Other than using the trick to remove all the fasteners on a 44 year old mast, used it to get corrosion welded bolts out that passed through substantial aluminum castings on my self steering vane.

Having said the above, the hardest fastener to remove is not one that is threaded into aluminum but one that simply passes through an aluminum casting like cleats, etc. Getting the bolts out of the self steering casting took something north of 25 iterations, heating with the jumper cable and quenching with penetrating oil over many days. A good idea to coat the shaft of any fastener in aluminum cleats or castings with Lanocote.