Stainless steel duplex stainless steels are achieved with an overall lower alloy content than similar-performing super-austenitic grades, making their use cost-effective for many applications. Duplex grades are characterized into groups based on their alloy content and corrosion resistance. Precipitation hardening stainless steels have corrosion resistance comparable to austenitic varieties, but can be precipitation hardened to even higher strengths than the other martensitic grades. The most common, 17-4PH, uses about 17% chromium and 4% nickel. The designation "CRES" is used in various industries to refer to corrosion-resistant steel. Most mentions of CRES refer to stainless steel, although the correspondence is not absolute, because
Marine grade stainless the stainless surface can be rinsed by rainfall, which will reduce the tendency for surface chlorides to concentrate by evaporation. Thus, the underside of overhangs will be more susceptible to corrosion due to lack of rinsing, also desert locations near the seashore will typically be more corrosive than seashores in locations with high rainfall. Visible evidence of corrosive attack in a marine environment is known as “tea staining”. Marine grade stainless Marine grade stainless steel is a misunderstood description. There is no industry recognized definition for a marine grade stainless steel though it is routinely used by many end-users. In