What are these white and brown stains on my kitchen sink and should I replace the sink?

[Skipsteer]

Kitchen sink is about 15 years old and need to replace the leaking tap.
However I cant seem to remove the white and brown stains on the sink, therefore I wondering if I should replace the sink as well?

Any ideas what the stains are and if they are just cosmetic?
Also how i might be able to remove them if keeping the sink?

Any suggestions or advice welcome. Thanks

 

[Wayners]

Common with those sinks.
They look good but need looking after.
Don't use bleach to clean though as will damaged surface.
Try composite sink cleaner and see how that works out.
DIY of internet will have it.
Don't scrub either with anything abrasive.

 

[dilalio]

Also dishwasher salt spread around and left for a few hrs does a good job - as it does on textured shower trays.