Stainless 303 is a free-machining austenitic stainless material that is not as resistant to rust as other material grades. This is due to chemical additives used during the free machining process which attract corrosion. 303 stainless also requires different bath chemistry than other grades to achieve passivation. Types 302, 304, and 316, are also austenitic and are more highly recommended for marine applications and other saline environments. Choosing a smooth surface finish, ensuring thorough cleaning of that finish, and adding passivation treatments may also be recommended to achieve optimal corrosion resistance. Passivation is when parts are submerged in a 30% nitric acid solution, removing iron contamination from the surface which could potentially lead to rusting.