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Uncoated aluminum boiler with brass group head corrosion risk? (lemmy.nowsci.com)

submitted 4 months ago by [email protected] to c/coffee

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Hi all,

I've got an uncoated aluminum boiler to replace the flaking one in my Gaggia Classic Pro Evo. Given that aluminum boiler coupled with the brass group head will cause galvanic corrosion, what are my options?

I know I can wait for companies to get chrome plated group heads in stock, but I hear the new (since April) GCP Evos are using the brass group head and the uncoated boiler. How are they pulling that off?

Thanks.

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[–] [email protected] 1 points 4 months ago (2 children)

My concern more stems from electrochemical replacement plating, where the water acts as a transfer agent.

[–] [email protected] 1 points 4 months ago (1 children)

Disclaimer that I have not worked on espresso machines in a bit.

When i did that was usually not a problem, swimming pools filters yes, espresso machines no.

Direct contact could be a problem, though not always. The bolts holding everything together were generally more of an issue, grease helped with that.

The most common issue i saw was caused by water with a high mineral content. But that was scaling more than deposition.

[–] [email protected] 2 points 4 months ago

Thank you. I'm using RPavlis water, so low mineral content.

[–] [email protected] 1 points 4 months ago (1 children)

but that only happens while there is water there, right? so given the limited amount of contact time i think this is not a concern. aluminum has a great capacity for self-passivation too, at least the typical alloys do.

[–] [email protected] 2 points 4 months ago (1 children)

Unless the Classic has changed considerably, it may have idk, the boiler and grouphead are bolted together. So there is always water there, the element would burn out otherwise.

[–] [email protected] 2 points 4 months ago (1 children)

ah ok i mistunderstood what the group head is. if they are both permanently in contact with the water in the boiler then it would depend a lot on the water quality. Water with only a little conductivity (<100µS/cm) would not be a problem for pure aluminium or most alloys, since the aluminium would passivate much quicker than the corrosion could dig into it.
i would assume that a vessel made for boiling water is made of a highly corrosion resistant alloy but i can not know for sure.

[–] [email protected] 1 points 4 months ago

I'm using RPavlis water, so hopefully that works out.