This sword is only from about the 14th century. It would've been mostly (if not all) steel construction, and it is obviously very seriously degraded by oxidation. Location is of course important. I understand that peat bogs tend to preserve things longer due to the relatively anoxic nature of the bog. But even so... steel will dissolve away in time. Bronze, however... doesn't oxidize. So curiously enough, there are often more quality examples of far older bronze age weapons remaining than there are of the more modern steel counterparts.
Bronze lost to steel on the battlefield, but won out in the test of the ages. Heh.