[daveson]

Hey all needing some help with a paper i'm writing for my uni course and thought you guys would be able to come to my aid , i'm doing a crime and investigative studies course and part of my paper discusses the different types of criminal and different methods used by maybe more sophisticated long term criminals, I was discussing these with one of my tutors who said there has been cases of burglars using chemicals like acid for example to compromise a lock on a door by pouring it into the lock itself to dissolve the pins inside thus enabling someone to turn the lock with a screwdriver or any other tension tool, I don't know how credible this is though it sounds too movie like to me my thought would be that if you pour acid into a lock it would melt the whole thing meaning that you would make it unable to unlock or work altogether or am I being naive? he also said liquid nitrogen sprayed into the lock to freeze the pins does pop up from time to time aswel but is a very rare one but also again if you did this wouldn't you freeze the whole thing thus making it impossible to turn with anything? I really need help with this as I don't want to be submitting false information but it sounds so ridiculous that if its actually a possibility it would make for great invaluable information for my paper , many thanks in advance for any replies they will be much appreciated

[Borek]

I don't see acid working on the tumbler lock - if anything, it will most likely dissolve springs first, making it impossible for the lock to work at all.

Liquid nitrogen will make the metal brittle: http://cons.wonderhowto.com/how-to/freeze-lock-off-69604/ (they don't use LN, but the effect is similar).

[daveson]

im with you with the liquid nitrogen im thinking it would freeze the whole thing then when you apply any pressure the whole lock would just break and there would be no way to open it with or without the key and prob have to end up breaking the door down anyway.
do you mean the springs for they pins? it would still prob take a hell of a lot of pouring for it to dissolve anything even the springs , am I correct in thinking this?

[Borek]

Spring are part of the tumbler lock construction, yes, they push the pins.

You don't need that much acid to destroy these springs, they are quite delicate.

[billnotgatez]

OK, So my powers of GOOGLE and WIKI have not come up with a successful acid safe cracking.
Even my search of Mythbusters does not have an acid safe cracking episode.
There was an article on an attempt to use muriatic acid, but that was just an attempt.
I could not find anything on Snopes.com either.

[Corribus]

Sounds like an awesome science fair project!

[Skarn]

If one were attempting to break a padlock, I could see both of those methods working.  Putting acid around the shackle may corrode it to the point that it could snap rather than open, but I daresay it would take a long time to get to a breakable point.  Liquid nitrogen sprayed onto the shackle would make it brittle, enabling it to break with the addition of some twisting force....maybe.

Perhaps the acid and LN are just to corrode/freeze the insides so that it would just turn to mush, rather than the pinpoint corrosion of some vital part.

[Arkcon]

OK, So my powers of GOOGLE and WIKI have not come up with a successful acid safe cracking.
Even my search of Mythbusters does not have an acid safe cracking episode.
There was an article on an attempt to use muriatic acid, but that was just an attempt.
I could not find anything on Snopes.com either.

We gave a similar question a through treatment in this old thread here: http://www.chemicalforums.com/index.php?topic=30128.0  Briefly, I doubt the original poster's story was ever seriously reported, but is instead an urban legend, if not actually a work of fiction.  The thread I quoted try to help a new poster understand not just the chemical concepts, but how to detect tall tales as well.

[vmelkon]

OK, So my powers of GOOGLE and WIKI have not come up with a successful acid safe cracking.
Even my search of Mythbusters does not have an acid safe cracking episode.
There was an article on an attempt to use muriatic acid, but that was just an attempt.
I could not find anything on Snopes.com either.

Muriatic acid? Why not call it hydrochloric acid (HCl).
HCl is not going to work on a bronze or brass lock. It requires HNO3.

LN2 could be used to make it brittle but I don't know if it would work on a lock. I guess you could damage the insides.

I have seen it done on a small home or office safe with LN2
You can use a sledgehammer to crack the brittle metal. It is very very easy to break.
I think they soaked the safe in LN2 for 5 min.
Breaking it into pieces takes 2 hits.