[nastybyte]

Hi,
i have a very nice coffee machine in which the heater is burnt (ground fault). The boiler is made of brass. Now my question is, does the heater have to be of the same alloy to avoid electrochemical reactions - i'd like coffee without a hint of Cu²⁺... Or can i use a stainless steel heater? Excuse me if my question is noobish, i'm organic chemist, not so sure where to look for info like this.

[Arkcon]

Generally, plain tap water doesn't have much of an electrochemical reaction with dissimilar metals, especially due to short duration.  Soon, traces of minerals precipitate as scale, protecting the surface even further.

[Borek]

You probably think about galvanic corrosion. Yes, in general it is better to separate different metals - they just have to be electrically isolated. Doesn't mean you can't use them both in the same solution, just don't let them touch each other nor don't connect them through an external circuit. However, that's a problem mostly when one of the metals is already prone to corrosion, when both are rather noble the risk is rather minimal.