It will not happen overnight, and I know you are trying to belittle me again, but it is something to consider anytime you have dissimilar metals .
It's NOT the metals alone that must be considered. It is the metals plus electrolyte. No electrolyte, no corrosion.
I'm not trying to belittle you personally, at all. But, your position statement is basically flawed and requires correction. I suspect it is from a lack of proper understanding regarding elemental chemistry. Or, perhaps you've been misinformed.
Also The floats are plastic and not brass.
The 550 has plastic floats molded to brass pivots. Some of the new floats are completely plastic. But, you haven't a shred of evidence this was done to combat corrosion. I suspect it was a cost reduction measure. You only seem to have speculation and myth with no supportive applicable science.
Start looking at where the corrosion is on the Honda carbs. It is not where the steel screws are located in the aluminum It is always near the float posts and main jet holder tube.
EXAMPLE:
...Yet your example picture has even corrosion deposits all over the carb body internals in pretty even distribution.
Galvanic action is distance critical. Meaning the shorter the distance between the dissimilar metals, the more activity results depending on the resistivity of the electrolyte. In fact, your picture demonstrates that the corrosion observed was not particularly associated with the brass components. It is NOT the result of galvanic action between brass and carb body alloy. More likely the water (the electrolyte), oxygen, from the atmospheric vents, disuse, and neglect was far more likely to be cause of the white zinc oxide deposits shown (converted from the zinc in the alloy bodies).
Since impure water (electrolyte) with dissolved oxygen collects at the bottom of the bowls, the (towers) are deprived of high resistance and protective gasoline at that carb body location. This leads to more corrosive activity at that location first. While the brass does not help matters, it is NOT the primary cause of corrosion. And specifically not a factor at the top of the fuel bowl reservoir as you suggest with your example picture.
