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This paper reviews new developments for stainless steel and nickel alloys now available for use in the marine industry. Properties of these alloys are significantly improved due to advances in their manufacturing processes over the last 30 years. Information is provided to assist in forming, fabrication, and post-fabrication cleaning of the alloys. Corrosion data are presented to help the marine engineer select the appropriate alloy. Cladding and wallpapering concepts are introduced and show promise as new and economical technology for corrosion protection. Examples of selected marine applications of the improved alloys are also provided. t NTRODUCTlONThe first stainless steels and nickel alloys were developed in the early 1900's. Additional alloy compositions were developed into the 1960's. However, in the past 30 years, the manufacturing practices used to produce the newer alloys have undergone a revolution and their service performance is vastly superior to their ancestors.A stainless steel is a low-carbon, iron-base alloy containing 10-1 8% chromium. Iron-base alloys containing more than 16% chromium are resistant to the formation of rust in most atmospheric environments -thus the term "stainless steel". The term "stainless" must not be confused with immunity to corrosion, as all of the alloys in the family can corrode if not properly matched to the specific exposure in the marine environment. Today there are hundreds of alloys that are in the stainless steel family. These alloys have a wide variety of properties, including a range of resistance to corrosion in marine environments.A nickel alloy is an alloy containing more nickel than any other elements. Major alloying elements for nickel alloys used in marine applications are copper, chromium, molybdenum, and iron. Other alloying elements, such as AI, Ti, W, and Nb, are also added to enhance corrosion resistance or age hardening. The nickel alloys are very resistant to marine atmospheric environments and also have a wide variety of properties, including a range of resistance to corrosion in marine environments. TYPES OF ALLOYS Stainless SteelsThere are five main types of stainless steel: ferritic, martensitic, austenitic, precipitation hardening (PH), and duplex.' The ferritic and martensitic grades are so named because of their crystal structures. Both are iron-chromium alloys and were the type of stainless steel first commercialized in the early 1900's. The ferritic and martensitic stainless steels are magnetic. The martensitic stainless steels can be hardened by a heat treatment similar to that used to harden ordinary carbon steel, namely, heating to a high temperature, quenching, then re-heating to an intermediate temperature (tempering) to achieve the desired balance of hardness and ductility.

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