Prebuy on airframe corrosion.
 

Any specific areas to be inspected for corrosion? Other outstanding issues a novice may need to be aware of, it's a 73 P with 3300 A/F hrs.

Bad spots I have found are on the interior, located on the inside surfaces of the skins. Cessna used lead vinyl "vibration absorbing" pads with a certain glue that holds water to attach them to the aluminum panels. If any water gets trapped, it causes the skins to corrode. I found a bunch of this on my 1973 337G restoration.

The fuel tanks can also have corrosion issues in the bay and on the tanks themselves.

Finally, around and under the avionics bay access hatch has a known issue. Others may have found spots to include to this list.

I just had to have my whole horizontal stabilizer reskinned due to corrosion, so I’d suggest looking inside there as well.

-Bjorn

Under the battery box all the way down to cowl flap including muffler support. In fact muffler supports both sides. Skin near and downwind from battery region and vent.

Wing roots under the fairings where wing joins fuselage. Those fairings poor at keeping out water. Includes wing attachment hardware. Struts can be overlooked (due to fair number of screws to completely expose those; also the fairings at the ends can be difficult to remove-mine we’re even riveted in place impeding inspection) and check those.

Bottom of rudder in case lower rudder tips poorly drain and hold water.

I have a super clean airframe, 1968 C model, but there was still corrosion under some of the dampening pads in the interior so that may not be the first place to look. Those are not easy to access either so I would check some easy spots first.

Like the previous post above on the elevator, I would closely inspect the trailing edges of the elevator and ailerons. These are tight areas that salt moisture can get trapped and will show corrosion first. Also pull the under wing panels and with a good light see how much white dust type accumulation is present. It can vary from none, with shiny aluminum to ugly battery acid look. Areas posted above that are easier to access will give you a good indication of the condition. Also just reviewing log books and history of location (internet search) will help to reveal any suspect reason to start searching in the harder to reach areas. Some of the areas are just a given that corrosion will be there. Most experienced A&P’s will know the task.

The last thing I would suggest is discipline yourself to walk away from a disaster after crossing several issues. Don’t get emotionally attached to the outside beauty of the Skymaster. Be prepared to expect the worst. There’s just a lot of junk out there. It takes time and energy to find the one.

Couldn't agree more Herb. I forgot about the trailing edge, and mine does have a small issue on the outboard RHS flap in that location as well.

ACF 50 / Corrosion X
 

This reminds me, when I was commuting for 22 years along the ocean to the Outer Banks, down low: Every 2nd or 3rd annual, when it's all opened up, have the entire airframe fogged with ACF 50 or Corrosion X. Stops the clock on corrosion.

Gentlemen, this information is extremely helpful. Again Thanks, Joe