The "300" series of Stainless Steel is the most common. It offers the greatest resistance to corrosion. They are austenitic, non-magnetic, and resistant to most acids. They cannot be hardedned by heat treating but when work hardened they can become slightly magnetic.
The "400" series will not progressivley rust but corrosion resistance is lesser than that of the "300" series. They are magnetic and are usually more inexpensive.