Alum for stud removal vs vinegar - garage experiment

[Zed Head]

I picked up some Mrs. Wages Alum from the local Coastal store.  Seems like the right stuff, although apparently there are various ratios of elements all called "alum".  The ingredients say "aluminum potassium sulfate", no indication of a blend.

Found two old studs from past disassemblies, both with nuts corroded/jammed on to them.  I try to save all of my odds and ends just in case, and I couldn't get the nuts off of these.  So they represent locked threads.  Added some water to the alum and it didn't all dissolve so it's a saturated solution.  Dropped the studs in to jars containing both the alum solution and another with apple cider vinegar, plus a drop of dish detergent in each to help break through any oil film.  Lets' see what happens.  No heat to start, just like a typical garage scenario.  I've derusted things before with the vinegar and it works surprisingly well.

Took some starting pictures, but it's just two salad dressing jars with rusty studs and unclear liquids in the bottom.  They have time stamps.  It's about 40 degrees F in the garage.

[black gold man]

See available in bulk http://www.myspicesage.com/alum-powder-p-531.html?gclid=CMfgt-671coCFQiKaQod8FoK3A

 

[Zed Head]

The Spice alum doesn't contain the potassium ion, according to their description, in your link.  Mrs. Wages does, apparently.  In solution there should be little difference, I believe.  Probably why they call them all "alum".  Mrs. Wages would be a lower purity form of aluminum sulfate maybe, or just offer easier purification by crystallization.

I found another old stud so made up a another solution, but heated it to get more alum in to solution.  Heat helped.  I'll see if it stays in solution or comes back out.

 

[Zed Head]

Most of the alum that was in the hot solution crystallized back out after it cooled down.  It's looking like heat is a big part of having a realistic method, time-wise.  Probably why it's popular in watch world, but not well-known in the world of big parts.  Heating a cylinder head and holding it there would be difficult.

I'll leave one in the cold and boil the second one tomorrow to see what happens.

[Zed Head]

Just a note for anyone deciding to try this.  I don't know what the gas bubbles are that released during the chemical reaction, but they should probably be avoided and/or dispersed.  I don't think that it's boiling water.  More likely either hydrogen, oxygen, or sulfur dioxide.  Two somewhat flammable/explosive, one is toxic.  The levels must be very low and dilute but still should be considered.  The rotten egg smell leans toward sulfur dioxide.  Aluminum oxide, iron sulphate (or sulphite?  I don't know), and sulfur dioxide could be the end products.  Maybe. I don't want to tax my brain with chemistry.

Any chemists out there feel free to set me straight.  The volume of gas from tiny watch screws is probably much less than from the large objects we're messing with.  We might be in dangerous territory.  Don't get poisoned or burned.

I did boil up one of the rusty studs last night and the red rust turned to black, along with lots of fizzing.  The stud and nut stayed black after the rust was gone, not shiny metal, and eventually I was able to remove the nut.  I have some pictures. I'll post up later.

[Namerow]

I had high hopes for this treatment but -- like many things that appear too good to be true -- I can now report that, after trying it out, this whole thing is 100% bogus.  My test piece was a spare distributor base casting, complete with the remnants of the snapped-off locking screw. I bought a small can of alum off the grocery store's cooking spices shelf and then dumped it into a small saucepan full of water.  After bringing the water up to just below boiling temperature, I dropped the casting in to see what would happen.

There was a lot of bubbling action, although it all seemed to be coming off the aluminum surfaces rather than from the area of the snapped-off screw.  After watching this for about a minute, I started to get concerned that the process was attacking the wrong metal (i.e. the aluminum, and not the steel).  I re-jigged the casting so that only the 'ear' with the screw shank was immersed in the water, and then let things go for about 20 minutes. There was still no sign of anything really important happening around the steel screw.

After the twenty minutes were up, I pulled the part out of the water to inspect it more closely.  As you'll see from the 'before' and 'after' pictures below, my suspicions were correct.  The aluminum had been eroded (you can see the etching lines from where the water surface was located).  The exposed surfaces of the screw shank were darkened, but that's about it.  I still had hopes that maybe the chemical action had attacked the corrosion between the screw threads and the casting threads, so I took it down to my workbench to see if the screw was perhaps now loose (or, at least, not as frozen as before).  Nothing doing.  It still wouldn't budge, and now I'm back to having to drill it out and re-tap the hole.  In addition, the 20 minutes of full immersion had 'pickled' the rest of the aluminum casting's surface, making it darker and -- well -- not as nice as it looked at the start, fresh out of the blasting cabinet.

End result:  Perfect alloy casting is now not so perfect any more, and the snapped-off screw is still firmly stuck in place.

Conclusion:  Don't waste your time on this 'miracle cure'.  It doesn't work and it will eat your aluminum parts.

[Zed Head]

My rusty studs cleaned up well but I also ended my experiment early.  It didn't loosen the frozen-on nuts either.  It's a messy process anyway.  Not right for the garage.

You didn't show before and after of the same piece of the part.  And did you try to clean the "black" from the mount?  Might be iron deposits, not etching.  20 minutes is waaayyy too short to see much.  Even straight sulfuric acid would take a few or more hours too dissolve the iron.  No offense, but most chemistry requires lots of patience.

Did you ever talk to your Chem. E. friend?

That part is small enough and the area the stud in is set up just right for heating to expand the aluminum.  I think that an EZ-out type remover and a torch would get it out.  Plus you can fit the whole thing in a drill press to get a good hole drilled.  Doesn't shed light on the alum question, but you can still save the part.

[Mark Maras]

I remember somewhere in the orig. info using hydrogen peroxide (h2-o2) vs h2o and alum. Anyone know how or if an extra oxygen molecule could affect this process?

[Namerow]

3 hours ago, Zed Head said:

My rusty studs cleaned up well but I also ended my experiment early.  It didn't loosen the frozen-on nuts either.  It's a messy process anyway.  Not right for the garage.

You didn't show before and after of the same piece of the part.  And did you try to clean the "black" from the mount?  Might be iron deposits, not etching.  20 minutes is waaayyy too short to see much.  Even straight sulfuric acid would take a few or more hours too dissolve the iron.  No offense, but most chemistry requires lots of patience.

Did you ever talk to your Chem. E. friend?

That part is small enough and the area the stud in is set up just right for heating to expand the aluminum.  I think that an EZ-out type remover and a torch would get it out.  Plus you can fit the whole thing in a drill press to get a good hole drilled.  Doesn't shed light on the alum question, but you can still save the part.

Sorry, but those are pix of the same part.  Just turned upside down in the 'after' shot. 

No way I was going to leave this part in this solution any longer than I did.  Too much action happening on the aluminum surfaces and I didn't want to damage the machine bore.  In any case, my experiment wasn't really about fixing this part.  Instead, I wanted to see whether this technique had any promise for getting the snapped-off manifold stud out of my car's cylinder head.  The distributor casting was just a guinea pig.

I just had lunch with my my friend the chemical engineering prof earlier this week, but we talked mostly about my zinc electroplating set-up and I forgot to ask about this other process.   If I pick up any insights in a future conversation, I'll let you know.

[Zed Head]

40 minutes ago, Namerow said:

Sorry, but those are pix of the same part.  Just turned upside down in the 'after' shot. 

Exactly.  You talked about erosion but you're showing different areas, one top and one bottom.  And the lines on the bottom are machining lines from when the parts was made.  Show the same area before and after, and after rubbing off the black material.  No offence, but your pictures don't really show evidence of anything but some black staining.

Edited February 27, 2016 by Zed Head