Tony writes:

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.

Urine isn't usually terribly concentrated. Some of the byproducts of
urine that are produced after exogenous microorganisms attack it (such
as ammonia) are much more damaging.

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