Aluminium does under go oxidation, although it is white. Unlike iron oxidation which is orange. If the tile is designed for use in a wet area it is probably coated or anodised to prevent white oxidation. Check if cleaning will be a hassle (risk stripping the coating).

Thanks for all the suggestions. I have used grouting the same colour as the tiles and finished with a smaller tile at the top allowing for a decent gap below the ceiling. I hardly notice it! Very happy with the result.

Hey guys! Looking for thoughts / feedback on a new product for preventing metal can rust stains on surfaces. We designed this coaster (below) that you can attach to the can base to prevent it from rusting and ruining surfaces, especially new ceramic or porcelain tiles. It can be used for most standard cans like shaving cream, air freshener or hair spray. Would really appreciate your thoughts / opinion about whether this is something you'd find useful, especially if you've just remodelled your bathroom. Thanks a lot, Irina

Hi Janet, there are glaze repair paints. I think Bunnings may stock a white knight product. Also found this one on amazon. I understand that you can tint the white with the colour required to match your tiles. You will have to purchase a small sample pot of the appropriate coloured paint to mix with repair kit. https://www.amazon.com/Shower-Repair-white-Toilet-Porcelain/dp/B07YZNMHXC. Also https://www.whiteknightpaints.com.au/products/kitchen-bathroom/white-knight-tub-basin/