Cast aluminium tarnishing

G'day all,

While I'm in the process of putting my engine back together, I want to sandblast all the cast alloy bits in the engine bay.

Does anyone know what I should use to stop them from tarnishing again?
I was thinking clear powdercoat but I've heard it can go yellowish.

Thanks.

From what I've read, Dupli-color Cast Coat seems the way to go.

Seems like all the other brands don't look like natural cast alloy.