You're just guessing.
Galvanic corrosion and stray current corrosion have clear, identifiable pathways of electron and ion flow. The direction of that flow is what determines which is the anode and which is the cathode. It can be confusing, which is why people are often surprised that with stray current corrosion the metal fitting that has the +voltage applied to it actually becomes the anode, even though with galvanic corrosion it's the more negative metal that becomes the anode. It's all about electron flow, and with AC they're just moving back and forth and not in a steady stream like DC, which is why AC requires very high (not 4 amps) current density to cause corrosion.
