A lot of those elements aren't stainless. They may look it but you'll find most are nickel-plated copper. A couple of mine have lost their coatings over the rigours of time. Most definitely copper underneath. :unsure:
Citric acid mixed at a ratio of 10g per litre of water will remove most scale from elements. You only need enough water to cover the things. Make sure you rinse it well afterwards otherwise your beer will taste like Solo. :blink:
When you say hard crusty stuff, does it look like ordinary kettle scale? (off-whitish colour, like you see around hot water heaters or kitchen kettles)
If that's the case, it's probably just calcium deposit from your water.
I think some sort of mild acid should do the trick - maybe even some white vinegar.
It is an off whitish colour and it probably is nickel plated copper come to think of it. Looks like the shiny half inch pipe they sometime use to connect to toilet cisterns.
Thanks for the tips.
Breezy