On Jan 26, 12:49 pm, "Tony" wrote:
Sigh.

It is not its pH that makes urine corrosive, but the dissolved salts
that become reactive. That's why cars that are close to the oceans rust
more quickly than do those in rainy inland locations.


Tony,
Here is another example of the corrosive effect of urine
http://tinyurl.com/26ghv8

"On the pitting corrosion of high strength aluminium alloys by rat
urine
Sreekumar, K; Jacob, E; Natarajan, A; Lakshmanan, T S
Praktische Metallographie (Germany). Vol. 34, no. 9, pp. 478-481. Sept.
1997

High strength AFNOR 7020 aluminium alloy sheets in T6 condition are
used for fabricating propellant tanks (nitrogen tetroxide N sub 2 O sub
4 and unsymmetrical dimethyl hydrazine UDMH) for launch vehicle
applications. These tanks are fabricated through welding route and are
filled with dry nitrogen gas at 300 mbar and sealed at both ends. The
tank is then cocooned with aluminised plastic sheets and stored under
positive dry nitrogen gas pressure. During the storage rats had cut
open the aluminised plastic sheets and had urinated all over the
surfaces of the aluminium alloy tank. The tank surface showed
discolouration and severe pitting corrosion attack wherever the rat
urine had come in contact with it. This paper highlights the
investigations made to understand the severity of the corrosion attack
on the surface of the tank with a view to clear it for further
processing and utilisation.

I'd bet someone will argue that rat urine is not the same as
human stuff. The counter argument is that some people are considered
'dirty rats' ;-)

By the way, the pH level of human urine can range from 4.5 to 8
and normal urine is slightly acidic.