Some clients coat it with paint. Other clean the stove polish now and then. You could start with the second approach and if it doesn't work for you, paint it at a later stage. See also: https://www.firebacks.net/blog/how-to-install-a-fireback-above-a-stove
Please let me know if you have any further questions.
Charles Nijman
Charles Nijman Fireplace Antiques