A simple test for the Stainless steel is a magnet test. If the steel is magnetic, it usually doesn't contain the needed nickel (which resists corrosion). Corrosion resistant stainless steel is usually a combo of chromium and nickel. Called 304 and is not magnetic.
There are some newer stainless steels that contain titanium along with the chromium. They are magnetic and don't corrode. They also are resistant to heat expansion. Called, 443 and used by the Japanese.