Texas instruments has decided to change from non-roughened leadframe to single-side roughened leadframe for some of its parts. For this reason these devices look as if they have been corroded. Roughened leadframes are an improvement to the older leadframe technology and provide improved solder adhesion.
The parts previously had a non-roughened leadframe as seen in the image below.
There is no reason to be worried if your leadframes look like this. The part will still operate correctly as per the datasheet.