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.
That is probably inspired by EN IEC 81346-2 where “X” indicates a connector of some kind and the numbers following the X identify the connector and the relative position on the connector (for connectors with multiple contacts).