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So I am using electrolysis to remove rust from a fuel tank. The tank is the cathode and a sacrificial anode is inserted where the fuel pump normally goes. It's not practical to put it anywhere else.

However, the fuel tank has internal baffles, apparently for anti-slosh. They have continuity with the tank, i.e. they are part of the cathode.

It cannot be denied that the the tank is getting a lot cleaner, and formerly-rusty areas are becoming shiny. And it's difficult to tell for sure, but subjectively, it seems like it's not doing so well in parts of the tank placed "in shadow" by the baffle, i.e. the baffle interrupts line-of-sight to the anode. This is more obvious where there are holes in the baffle.

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My setup, and what seems to be happening.

So my question is: Is line-of-sight a requirement for electrolysis? Does electrolysis happen through the electrolyte (acting on all wetted surfaces) or does it only use the most direct path between anode and cathode?

Electrical current takes all paths in proportion to their conductance... so will the path through the electrolyte around the baffle eventually have effect?

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    $\begingroup$ Direct visibility is not required but the cell geometry may significantly affect the electrostatic potential field, electromigration, diffusion, local availability of active components and reaction rates. $\endgroup$
    – Poutnik
    Apr 30, 2021 at 5:43
  • $\begingroup$ Your setup looks like the baffle will prevent adequate treatment of the tank wall. Have you considered something like a rust conversion treatment, like Naval Jelly, which you could slosh around (if you buy enough)? It's mostly phosphoric acid with a thickener. $\endgroup$ Apr 30, 2021 at 16:00

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