thanks, probably the best working code dealing with the subject. I replaced the datetime with time(0), just easier on my eyes:
CAST(STUFF(STUFF(REPLACE(STR(run_time, 6), ' ', '0'), 3, 0, ':'), 6, 0, ':') AS time(0)) AS runtime,
CAST(STUFF(STUFF(REPLACE(STR(run_duration, 6), ' ', '0'), 3, 0, ':'), 6, 0, ':') AS time(0)) AS duration