....On "Park Avenue" style sidewalk canopies, the framing system has evolved
from a pipe-assembly style c. 1930 (beautiful 1.24 inch pipe with special
pin-fittings) to the off-site assembled welded steel frames. These frames
appear to be galvanized, and rust free (except for Ralph's building, because
he urinates out the window), but the welds always rust.

Do the welds rust because the welding process violates the galvanized area,
or because some material applied in the welding process is rustable?

Sign me,   Taxi, Miss?