Having been located on Catalina Island for much of its life wasn't corrosion a problem or wasn't it ever allowed on what was a much cared for aircraft?
While we owned the aircraft we had to do a major wing spar modification that required that the wings be removed from the aircraft; which is a long story in itself. Seeing as how the aircraft was to be taken apart so much I had the company doing the mod to perform a intensive corrosion inspection on the airframe. They found shockingly little corrosion, just some small areas on the fuel tanks that were treated and repainted.
There was no doubt that the aircraft was very well maintained while the Wrigley's and ourselves owned the aircraft. We did not operate the aircraft that much, around 300 hours in a little over 3 years, but I made sure the engines were ran every week and we flew it once a month, if just around the pattern.
Sadly it appears that the aircraft is not is such good shape today from some pictures I found on her in Bakersfield, California. I'm off line right now, when I get back on the internet I'll post the link.
Oh, one other point, in my experience corrosion is not the problem in Southern California as it is in Florida and the Gulf Coast. Why, I don't have a clue.