Doesn't it encourage galvanic corrosion, which affects both?
Depends .. aluminums..
If the alloy is 7000 series it contains Zn.. (thats what the 7 indicates) 7005, 7075.
(C + Zn works for a battery)
If 6000, it doesn't, contain Zn. Ala 6061..
titanium is used as piping for really nasty fluids, way off the Ph 7 neutral .
Acids and harsh alkalies