i havent tried this myself but it was featured in classic mechanics- as well as a tip of placing ball bearings in the tank and shake to remove loose rust( dont know wether i would try the ball bearings myself)
http://www.frost.co.uk/result_search.asp i think the kit is just a rust inhibitor and coating of zinc phosphate
[Edited on 3-10-2005 by monstermob 998]