View Full Version : Bolt extraction from Aluminum using acid

11-14-2017, 01:42 PM
Here's something I stumbled upon when browsing on the internet:

I have a broken exhaust stud at cylinder 5 (deeper under the cowl than on a Sprinter) and 'something' at the bottom of the injector hold down bolt hole on cylinder 1 (which means I'm using a shortened bolt).
So this technique will be useful when I have to replace injector 1 and in case the exhaust manifold gasket burns through.

Once I get my hands on some alum, I will try a drop of solution on the cylinder head cover to check if it does something to it.

Aqua Puttana
11-14-2017, 03:24 PM
Wow. Thanks for the video link.

By the demonstration the technique works on I-ron (as he called it)... mild steel studs. I wonder how it will work on hardened steel like a broken tap?

Maybe I need to buy some alum and throw an old tap into a mixture.

Or maybe just watch another video.



P.S. - Gotta love his narration style. :thumbup:


11-14-2017, 05:16 PM
Buna and thanks for sharing! This may come in very useful sometime when in a pinch.

11-15-2017, 12:12 PM
You're welcome guys! I'm glad I could share this.

I'm really curious to try it, as I was thinking about all sorts of ideas to remove whatever is at the bottom of my injector bolt hole.
It seems unusual for 10mm of the bolt to break at the bottom and chances are it's some carbon which fell down during an old black death repair. But if it's steel, the solution is there.

11-15-2017, 03:48 PM
But, but, the dealership sez a broken bolt requires a complete new crate engine.....and a new transmission that is tuned and matched to the new engine....and new tires...or the van will EXPLODE and hurt innocent children and puppies. Broken bolts are serious business!

Aqua Puttana
11-15-2017, 04:00 PM
Is heat absolutely necessary or does it just accelerate the process?

If heat isn't needed, and you have time, my vision would be to use smurf tube or other corrugated plastic tube to glue to the aluminum and form a vessel. Some types of plastic tubing should handle the heat from a 7 watt lamp as used in the video.

Using the alum method would require removal of the exhaust header to get down to the stud and aluminum only. Obviously the iron exhaust header can't be in the mix.


11-15-2017, 04:59 PM
Is heat absolutely necessary or does it just accelerate the process?
Armwave: Raising the temperature 10 degrees C (18 F) roughly doubles the speed of any simple chemical reaction.
(so sez 55-year old memory of junior high chem class)

BUT: further digging coughs up that warming is needed... if only to dissolve enough alum in the water to reach a decent concentration (another thing that speeds up the reaction)
The 1st video mentions hydrogen peroxide... its effect is to generate heat.
Suggested amounts are 4 tablespoons of alum to 1 cup of water. Expect it to take 12 hours to dissolve the stud.

Alum is potassium aluminum sulfate (KAl(SO4)2), but the same name can apply to aluminum ammonium sulfate, or even simply aluminum sulfate. (there are many others: https://en.wikipedia.org/wiki/Alum#Types )
... i'm still trying to find the actual reaction chain.
One explanation (https://hackaday.com/2015/08/03/dissolve-steel-drill-bits-in-alum-from-the-grocery/) was: "The alum oxidizes the metals. Both metals ‘rust’ but for most brasses and aluminums the oxides act as protective layers. For ferrous metals the iron oxides flake off rather than stay bound to the metals underneath." ... another site properly used the word "passivates" to describe what was happening to the aluminum.

As the 2nd video shows, acids (nitric or sulfuric) also work. Same passivation effect. Alum's safer.

This EPA wastewater-treatment document (https://nepis.epa.gov/Exe/ZyNET.exe/P1001QTR.txt?ZyActionD=ZyDocument&Client=EPA&Index=2000%20Thru%202005&Docs=&Query=&Time=&EndTime=&SearchMethod=1&TocRestrict=n&Toc=&TocEntry=&QField=&QFieldYear=&QFieldMonth=&QFieldDay=&UseQField=&IntQFieldOp=0&ExtQFieldOp=0&XmlQuery=&File=D%3A%5CZYFILES%5CINDEX%20DATA%5C00THRU05%5CTX T%5C00000016%5CP1001QTR.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h%7C-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=hpfr&DefSeekPage=x&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=1&ZyEntry=4) describe's alum's action as "...when dissolved in water produces acidic condtions."
...so i assume the black chunk left at the end is iron sulfate.


Goofy foot
11-15-2017, 07:09 PM
I nominate this narrator for President !!

Patrick of M
11-15-2017, 10:42 PM
Esti Tabarnac, ša c'tait quelque chose!

Aqua Puttana
11-16-2017, 12:08 AM
Holy fak!! I agree.
(Apologies. My Quebec experience is mostly based in Hudson.)

:cheers: vic

11-16-2017, 09:57 AM
Using the alum method would require removal of the exhaust header to get down to the stud and aluminum only. Obviously the iron exhaust header can't be in the mix.


Yes indeed, it will be out.

If the gubernment won't tax us ridiculously starting next year and I can keep the car for another 3 years, then at some point I will want to fix the broken exhaust stud(s) and put in a set of new injectors.

The old incandescent 24v work lamp is still kicking around the garage, no problem with heat generation.