Many people use Corrosion-X and other products and believe it helps. I personally do not use the stuff, as I don't want to be constantly cleaning it up as it weeps through lap joints in the skins. When it finally quits weeping, it's time to retreat, so cleaning up after it becomes a fact of life. It also leaves a sticky residue inside, which accumalates all manner of dirt, debris, and bugs, and I don't see how that solves any corrosion issues, other than hiding it. Each to his own!
I'm starting to believe the same thing. My plane was Corrosion-X'ed about 6-7 years ago and the stuff is
still slowly weeping. The inside of the wings have a wet, oily sheen to them which acts like flypaper for dirt.
At best, I'm a fence-sitter on the efficacy of Corrosion-X: If it works, I'm glad it was done to my plane. However, I won't be renewing it - it looks like there's enough already.