From a previous question, it was recommended that for Portuguese custard tarts to use galvanized steel or aluminum molds, and also that the oven be heated to minimally 250°C (482°F). This video at ~2:49 has the oven temperature at ~380°C (716°F) so putting the oven to as high as possible does seem right.
However, in a comment right underneath, it noted that at these temperatures the zinc coating may strip, and while this website seems to concur in that the highest recommended temperature is 200°C (392°F) for long term exposure, it stated that 350°C (662°F) is fine for short term (<2 hours) exposure, which is definitely within the expected range of baking the tart, and also far from the temperatures that usual ovens can produce.
However, I'm also wondering about the differences between using different other mold materials like stainless steel, cast iron, carbon steel, tin foil, silicone, etc. in mainly how long they should be baked, but also whether there's any difference in baking methods (i.e., bake for x minutes, then blast underneath the broiler for y minutes).
Best Answer
The oven might be at 380, but the tins are certainly not: they're in contact with the pastry, after all, which cools them down. You'd know if they actually got that hot because the tarts would be on fire. (Not burnt. On fire.) So there's no concern with the zinc. The tins are thin enough that the difference in thermal mass and thermal conductivity between, say, carbon steel and aluminum wouldn't make much difference. And non-stick-ness wouldn't be an issue either, because of the high fat level in the crust. So really, any of the metal options would be equivalent. Choose based on price, durability, and ease of cleaning.
Silicone wouldn't work well (and is a bad idea for baking dishes in general). It has extremely low thermal conductivity compared to metal. It wouldn't crisp the crust effectively, and it could definitely break down in the heat.