I have a steering component off of a car that is a casting of iron or steel. It had some soft aluminum inserts pressed into it, which needed to be replaced, and I got them all out except one which has corroded itself into place really well.
I have tried to get the part out, by can’t even loosen it. I have drilled it as much as I dare, in an effort to thin the piece and then get it out, but that hasn’t worked as it usually does. I am afraid to drill any more because I may get through the aluminum that is left and damage the seating area in the iron housing that it sits in, which would prevent me from being able to re-use the housing.
The part is only about 1/2" x 1/2", and there isn’t much of it left. Does anyone know of something that I could soak the part in that would dissolve the aluminum without dissolving the iron housing? Maybe a chemistry knowlegable Doper knows something that will eat away at aluminum that won’t hurt iron.
Sodium hydroxide (red devil lye) will react quickly and completely with aluminum.
NaOH shouldn’t react much with iron or steel, and sometimes is used for cleaning such parts, but I’ve never actually tried it on auto parts. Test it on a a small area first.
You could try soaking it in vineger, but that may take a while. Hydrochloric acid would be faster if you can get , but don’t leave it in too long because the iron will dissolve slowly. On the basic side, a solution of Draino might work. I don’t think that will hurt the iron, but you might want to test it first.
If you use solid Drano, you’ll want to pick out the pieces of aluminum in the product before adding water. Those are what make Drano foam, but they’ll compete with the aluminum in your steering component.
If all else fails, many automotive machine shops now have laser machining devices for removing broken off screws and the like. The time I took a part to such a shop the hole looked like the original thread the job was done so cleanly.
I’ve heard of people having good results using ammonia to get aluminum seatposts out of bicycles. I’d advise against any solution involving heat, as aluminum expands more than iron which would just get the aluminum part stuck in harder.
With a ductile material like aluminum, heat can work. As you say, the aluminum expands more, but that means it extrudes lengthwise a bit. When the part cools, the aluminum shrinks to a smaller diameter than it was orgionally.
I’d go with the lye though. I’ve used it to strip aluminum plating from the ends of steel exhaust tubing prior to welding, and as indiated above, it doesn’t touch the steel at all.
BTW, the opposite problem (steel needing removal from an aluminum part…typically a broken tap) can be solved with nitric acid.
For more information on such tricks, google “proprietary solvent”
Just a safety warning, draino (lye) and aluminum reacting have an abundance of by product, namely Hydrogen. Make sure you are clear of any igintion source, lest you suffer the dreaded “Hindenburg Effect”.
Yes and wear gloves, goggles and long sleave shirt w/ pants. A smock if you have one. Any spill and don’t wait for it to burn, run to the sink or shower.
On the basis of waterj2’s comment, which is true - how about liquid nitrogen to shrink the part away from the iron? You might be able to get liquid nitrogen or “LN2” from a hospital, or from many industrial sources. Watch out about touching the part with wet fingers, though - imagine licking a cold flagpole, then imagine it happening 100X faster.
Thanks for all the information. I think I will look into the lye or Draino method.
I don’t want to apply signifcant heat to the housing because it has a straight bore in it for a valve to slide in and I don’t want to take a chance in warping the housing with heat.
I don’t think the heating and shrinking will work because the part is more than stuck in the housing, it is corroded into it. That is why I need something to disolve the aluminum and corrosion and leave the iron underneath.
I know there are machine shop methods of getting the aluminum out, but the cost of this would exceed the value of the housing. I want to try a “poor boy” homebrew method.