I don't think it will work. KOH is about like NaOH, in other words a
strong base. If you heat it, I'd think it would behave like a hot
caustic cleaning solution. Very tough on grease but won't touch rust.
The thing about rust is that if you put rusty steel into an acid
solution the acid attacks the rust much faster than it attacks the
steel. So if you put it in acid for the right length of time then
it will dissolve away all the rust but leave just about all the base
metal.

If I had to clean a car engine I'd certainly start with a grease-removing
soak followed by very hot water. Scrub it to make sure it's clean and
repeat the hot soak/rinse/scrub cycle until it is.

You know the problem with an acid soak on an engine block? How can you
guarantee that all the acid gets neutralized and rinsed away? I might
use a weak acid and longer soak followed by really serious rinsing.
The last rinse cycle should be in water hot enough so the whole block
will self-dry within 60 seconds.

Grant

nattydreadlocks wrote:

can anyone tell me if potassium hydroxide is any good at removing
rust? i am going to boil it(mixed with water) at about 200f and use it
to remove rust from a car engine. what do you think?