Character Replacement In Strings?

How fast can I replace characters in a string?

So the background on this question is this. We have a couple of applications that communicate with each other and with client's applications through sockets. These socket messages contain non printable characters (e.g. chr(0)) which need to get replaced with a predetermined string (e.g "{Nul}"} because the socket messages are kept in a log file. On a side note, not every log message will need to have characters replaced.

Now I started off on this little adventure reading from This MSDN link which I found from a different post from this site.

The current method we used...at the beginning of the day...was using string builder to check for all the possible replacements such as...

Public Function ReplaceSB(ByVal p_Message As String) As String
Dim sb As New System.Text.StringBuilder(p_Message)
sb.Replace(Chr(0), "{NUL}")

[Code]....

This so far has been the fastest way I have found to process these messages. I have tried various other ways of going about this as well like converting the incoming string into a character array and comparing along with also trying to loop through the string rather than the chrArray.