A lot of the alloy steels readily form a surface oxide (rust for lack of better terms) that actually protects it from further corrosion. That may be the even brown coating that you are seeing. Steel tubing is rarely "silver" in color without some sort of cleaning procedure. What I would consider true "rust", is the loose powdery/flaky stuff that has a gritty texture. The surface oxide will have a smoother feel to it.