I dunno about Terraclean. There seems to be alot of 'snake oil' comments about it being thrown around, as opposed to walnut shell blasting which seems to be the tried and tested gold standard.
http://www.e90post.com/forums/showthread.php?t=718641
and
http://www.e90post.com/forums/showthread.php?t=714808
Just a couple of links to some talk about Terraclean over at the 3ers.