remove all lines with nullbytes/corrupt data

To remove lines that contain byte 0 or bytes 128 to 255, you can use:

perl -ne 'print unless /[\0\200-\377]/'

Or with GNU grep built with PCRE support:

LC_ALL=C grep -vaP '[\0\200-\377]'

See also the strings command to extract what looks like printable text from data.

To just remove those bytes:

tr -d '\0\200-\377'

You can try with this Perl command:

<in_file perl -lne's/\0//g; print if $_'

in_file is the input. Pipe redirection can be used.

It removes NULs globally. You can adjust the regular expression to suit your needs.

You can remove all lines of yourfile that contain a null byte with gnu sed by

sed '/\x0/d' yourfile

This also works in a pipe:

cat yourfile | sed '/\x0/d'

You might be able to use strings with a minimum length of, say, five characters

strings -w -n5 corrupted.txt

Yes. You can do it like this:
sed -e '/\x00/d' [filename] > [new_filename]
If you want to edit the file in-place:
sed -i '/\x00/d' [filename]
You can also, combine the two, change the original file and keep a backup copy:
sed -i~ '/\x00/d' [filename]
That will delete any line of the file that contains at least 1 NULL.