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.

  • @[email protected]English
    2•3 months ago

    Isn’t there a gasket between grouphead and boiler? I would think a liberal amount of Dow 111 would be what you need. I haven’t had one of those apart in years so I can’t remember how it goes together exactly.

    • fmstratOPEnglish
      1•3 months ago

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

      • @[email protected]English
        1•3 months ago

        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]English
          2•3 months ago

          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]English
            2•3 months ago

            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.

            • fmstratOPEnglish
              1•3 months ago

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

      • @[email protected]English
        1•3 months ago

        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.

        • fmstratOPEnglish
          2•3 months ago

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

  • @theRealBassist
    1•3 months ago

    According to this chart which specifically looks at baseplates and fasteners, the brass will cause the aluminum to corrode, but not vice versa.