I don't think '铬' in this sentence means chromium, but I couldn't find other meaning except chromium in dictionary.
Is it a typo?
There are lots of chemical elements with unique Chinese characters, newly created to represent them.
Linked here is a very detailed post about the periodic table on Language Log, a well-reputed linguistics blog, in case you are interested in learning more about the general challenges/issues of talking chemistry in Chinese.
I think this is a typo, common mistake in Chinese Simplified Characters usage.
I guess the right word is 烙
烙 means : use fire to heat the iron then seal to the crimial's body, is a punishment, the brand will never fade on the skin and in their mind
Other posibly is 銘，means carve
烙 and 銘 here is almost the same meaning
full sentence : 那遍佈的傷疤，烙的她手指生疼