Bath stain - HELP

[Maraudersmap1]

I'm really struggling to remove this stubborn stain that's on the bottom of the bath. Just wondering if there's anybody who can recommend anything, it's an enamel bath and the staining has appeared under where the mat has been. 🙈 I've tried multiple cleaning solutions and given it some serious elbow grease but to no avail 😡

My late mother used to cut a lemon in half, dip it in bicarbonate of soda, apply that to any stains on an enamel bath, leave it overnight and rinse. Repeat as necessary for stubborn stains. If the enamel was in good condition it wouldn't harm it, but if the bath could already do with resurfacing then it would add to the general vintage or shabby chic appearance - I don't think my mum had heard of vintage or shabby chic at that time though!

Thanks I'll try it out!

Calcium dissolver and bathroom duo glove from Enjo. Chemical free cleaning