In message , alan_m
writes

I once bought some brass screws to fit a toilet pan to find years later
that the were brass plated screws (or brass coloured metal plated) and
the heads under the plastic cover were so corroded that the head had to
be drilled out.

grin Brass plated screws are horrible things. The ones I removed
from the pan are real brass and will go through my little tumbler for
reuse, good as new.
--
Graeme