I just Googled Ospho. From the description, it sounds a lot like something called POR15 that my younger brother uses when restoring old motorcycles. That stuff is formulated to put a stable oxide coating on ferrous metals. I think that is the opposite of what we are looking to do here. Here, with stainless, we want to strip the ferrous ions from the surface so that a layer of chromium oxide can form without blemishes. I think (& I could be wrong) that the stuff you have is good as a base coat for mild steels. Please let me know if the label recommends it's use on stainless.
Thanks,
Jim.