Its not customs that has a problem with star san its the airlines. As a hazardous material it isn't supposed to fly. 5 star chemicals (producers of SS) replied to my inquiry on the topic with a "You can't take it on a plane".
That hasn't stopped plenty of people from doing so, but just be aware that it could be confiscated. Don't put it in your carry on. Make sure the lid is on tight and consider wrapping duct tape for an extra level of sealing.
I would NOT wrap it with duct tape. That will look very suspicious. They seal it just fine. You wrap it I will bet money they open it then.