In the past, we have had questions about cleaning Asterite sinks.
I have come up with the following approach in a hard water area:
Use Cif bleach-based cleaner day-to-day.
Use heavy duty descaling techniques (e.g. brick acid). Sluice down the bowl. Allow lots of water to flow so that any acid is taken well down the sewer.
Use reasonably strong bleach. Allow to soak for a while. Sluice down well.
Repeat the last two steps if needed.
This does work. The sink does become bright white. But it seems to get stained again ever more quickly. I appreciate that this harsh approach might be affecting the sink itself but lesser techniques have never worked. (We got to the stage of saying that if this didn't work a new sink was in order. That has now been put on hold indefinitely for various reasons.)
Now I am wondering if there is anything that could be applied to the newly cleaned sink to prevent it staining again so quickly. Ideas that passed through my mind`included the Lithofin products. I am hoping for some tried and tested approaches (I mean, how many test cycles would you wish to go through?) but actually expect a load of untested ideas like 'Have you tried routing your condensate drain though it?', 'What about a Sicily of lemon juice poured down daily?', 'PVA', 'car body filler', 'Try cutting it with a hacksaw', 'Danish oil', 'anti-burglar paint'. Now surprise me with excellent ideas - whether practical or amusing or, dare I hope for it, both.