I bought 48 x 30cm from US just as brass went through the roof. Delivered express cost me about £80 - €120 (in those days). I thought I had recieved an empty box, seriously lightweight. The idea was for sidings, steam/battery power or possibly a portable layout. In the end I have used it as a temporary layout, just to see if my "plan" would work.
I can say that after 5 months (maybe more) outside it is still very bright compared to my Aristo brass which has weathered nicely. There is oxide present but it is not exactly white powdery more silvery grey and quite hard ( I think aluminium oxide is used as a blasting media and also "sandpaper"). Must admit to not having tried running track power lately so cannot say if it needs a good scrub first.
I will say that the fishplates are pretty weak in my opinion, they bend very easily and 3 or 4 sections joined together have a significant sag when you lift them up. There is also a fair bit of corrosion if you join to dissimilar (ie. brass) track , a bit of your coppaslip or graphite would be good here.
