To increase TMT bars' resistance to corrosion, particularly in harsh settings where they are exposed to chemicals and moisture, chromium is added. On the surface of the bars, chromium creates an oxide layer of protection that prevents corrosion and prolongs the bars' useful life under harsh circumstances. https://medium.com/@raja.raghu80/steel-strong-how-indias-steel-industry-shapes-its-economic-frontier-f92d8af0ea75