Too many variables to be able to determine how aircraft wreckage will deteriorate over time, as Ric and others have pointed out.
Feel free to add to the list...
Environment
Location
Depth
Quality of materials used in construction (1930's)
Quality of coatings on surfaces, paint etc (1930's)
It's only my opinion but, the Electra didn't have a lot of paint on it to start with in comparison to say, a Corsair, Avenger or Devastator etc... and, the location of the debris field isn't exactly ideal for preserving features like paint, or even aluminium for that matter. Yes, aircraft have been found with paint jobs intact but, under more favourable conditions, lagoons, flat sea beds, shallower water etc...
IMHO of course