A paper in the Journal of Archaeological Science reports the first confirmed existence of chromium iron (aka stainless steel) not as a 20th century creation, but the 11th century in Persia.

Chromium crucible steel was first made in Persia

Abstract

For more than a century, evidence for the production of crucible steel in Central and Southern Asia, prior to the European Industrial Revolution, has fascinated and challenged material scientists, historians and archaeologists. At the same time, chromium-alloyed stainless steel was developed in the early 20th century, building upon 19th century experiments with low chromium steel. Here we demonstrate new evidence of the intentional addition of chromium to steel nearly a millennium earlier, as part of the Persian crucible steel (pulad) tradition including the production of low-chromium crucible steel in early 2nd millennium CE Persia. We analysed archaeological finds from the 11th c. CE site of Chahak in Iran showing the intentional and regular addition of chromium mineral to the crucible charge, resulting in steel containing around 1 wt% chromium.

My immediate response to reading this was to remember the Mehrauli Iron Pillar in Delhi, India, which dates back to the 5th or 6th century CE.  It wasn’t stainless steel, but the pillar does not rust.  More than spices and cloth were traded along the silk road, so were ideas.  Travellers carried books, and it is less than 3000 kilometres from Mehrauli to Iran.  Is this an example of ideas taken from one place and improved upon by others?