In the FDR wewbsite we have:
http://www51.honeywell.com/aero/common/documents/Flight_Data_Recorder_%28SSFDR%29.pdf
In page 9 you can see the kind of protection to the PCB where the FLASH MEMORIES are soldered.
This protection is the first layer.
If the PCB is corroded an alternative is RESOLDER the ICīs in another PCB.
A third alternative would be read the content of each chip in the manufacturer.
IMO the chances to READ ALL DATA are high.
Finger crossing.
PS
We can suppose the new cylindrical shape is more survivable than the one showed in the product link. The former seems very tight.
We learned they are using the cylindrical shape as observed by Nick L at Post #424:
The drawing on the Honeywell data sheet is not correct for the "4X" (4700) series recorders. It is only correct for "1X" and "2X" models.