The oxygen is
essential in that case though.
In this case of this aircraft it's fair to say that at rest in normal conditions the Titanic would rust far more quickly than a modern airliner with many composite parts, it's also fair to presume that saline rusting of either would show the same balance.
Presuming that the mounting points stayed intact, that the boxes didn't sink into the mire and that the boxes weren't smashed in the crash event... I reckon about three years before the chips decay. Less time for any tape, sadly. A short article on the subject from
NBC, not very illustrative.