the sirio p 5000 and turbo models are not stainless.....just the whip is stainless. the ball joint and the mast that holds the whip is triple chrome plated brass. i came across a post somewhere where someone had a problem with the chrome plate starting to pit in that joint causing high swr issues. i also had a corrosion issue with the steel plate over the ferrite with my 1000 mag. it corroded to the point when it stated loosing what little capacitive ground it had leading to swr issues, which is why i bothered with the 5000 in the first place. however, i have come up with a way to kill the corrosion problem all together with the wilson mags, and i am going to try it out on the sirio as soon as i get the chance( was hoping that someone else had tried something similar). seems like we are in the middle of the rainy season here in the northeast, looks like sat or sunday will be the better days.