change the format of the minute

Hello,
Richard Buttrey kindly propose me yesterday to use the next formula:

=HOUR(B2)&MINUTE(B2)&SECOND(B2)&IF(SECOND(B2)=0,0,"")

to change the format from
5:39:00
to
53900

The problem is that when the time is between 5:00:00 to 5:09:00, the “00” transforms in “0”, and the "09", just in "9":
5000, 5900.

How could I make to obtain the first zero, like in “50900”?

Thanks

Try

=TEXT(B2,"hmmss")

Thank you very much, Daddylonglegs,
that was what I need.