If you have a water softener, the regs somewhere I can't quote, say you must have a non-softened tap, traditionally the kitchen sink.
Any aluminium surface exposed to atmosphere will oxidise pretty quickly. All the stuff in the condense trap is oxidised. Not quite the same as big Al ox crystals used for abrasives though. Anodised Al is oxidised, not exactly sharp though is it.
The oxide IS protective, though the layer is thin. A strong alkali will disrupt it, such as sodium hydroxide. Weak acids such as in condensate, will repair the protective coating.
The Worcester casting are pretty rough - check a new one sometime. In the first year or so you do get a tablespoon of Al out of them which blocks the condense trap nicely. After that, hardly anything comes out of them, so I don't think it's a serious problem.
Ally hexs have been around for a number of years now, and there simply aren't
screams of woe from people where they've "dissolved".
It may be going on to some extent, plumbers tend to chuck out failed parts rather than analyse them, so we don't know a lot about whether hex failures are due to corrosion or some other problem.
I've been watching and listening about "water conditioning" over the years. There's some good science saying how some of them can work a bit some of the time, but after that it all gets flaky. Some of the anecdotal evidence is compelling, but guys eg in water heating business like Andrews, who want the answers but don't actually make the conditioning products, find they can't repeat the results reliably. Sometimes they do nothing at all. I have to conclude that there's more, that we don't know yet.
What I find revolting is that some of the people who make the things have not the slightest clue what they're talking about. I collared the boss of Hydroflow one at a plumbing exhibition. I asked questions, and more questions, and he went off into orbit in a fantasy world about electric waves and chains of water molecules - for which there's no evidence. When he found out I have degrees in metallurgy & materials, and also electronics, he said it was only theories. AH
. The annoying thing is that the Hydoflow devices DO seem to work well SOME of the time!