Cleaning sinks
Stainless Steel
Asterite
These sinks are terrible to clean, but with the right chemicals it is possible to keep them nice and clean.
Mfrs recommend a cream cleaner with bleach.
A far more effective option is biological washing powder paste. Wet the sink, sprinkle a very thin layer of powder on, and wipe it over the sides as well if needed. Just leave it for as long as practical, ie hours at least. Very effective indeed.
Bleach doesn't remove dirt, it just decolourises it. And the rough absorbent dirt surface becomes dirty again relatively quickly.
Surface scale builds up in hard water areas. Brick acid will remove this, albeit slowly. Repeated application is needed to remove visible deposits. If desposits are heavy, eg around taps, a plastic scraper can be used to scrape over the scale surface (not the asterite!), and press down on the scale to help break it up.
Never let acid and bleach mix, either in the sink or the drainage trap. The 2 together produce chlorine gas, which is fatally toxic.