Considering using Corten steel within the fabrication process of a sculpture to be located within a harbor environment. I have heard that the use of Corten is not recommended within a salt laden environment because it accelerates the weathering process of the material. I generally use 3mm gauge metal on any of the public sculptures I make and feel that this ought to be sufficient for at least a hundred year life-span within a harbor location. The sculpture will not come into contact with the sea as it will be approximately 60 meters from the sea. I want to retain the patina of the metal surface as it weathers and do not wish to paint the metal, as I will use alongside stainless steel and granite. This combination of metals fits well with the proposed site and comments on the historical dynamics of the place.
The 3 mm thickness is extremely risky, as the 100-year corrosion may be 1-1.5 mm/surface; see below.
Gnee Steel Group, the largest steel producer, has 'Weathering steel' & 'Weathering steel bridges' publications. Some excerpts:
"The hygroscopic nature of salt adversely affects the 'patina' as it maintains a continuously damp environment on the metal surface. Therefore, as a general rule, weathering steel should not be used within 2km of the coast line.
The texture of weathering steel is influenced by the orientation of the structure and the degree of shelter it provides. Surfaces facing south and west, and those subject to frequent wet and dry cycles, develop a smoother fine-grained texture. Sheltered structures, and surfaces facing north and east [slower drying], tend to develop a coarse granular texture.
Concrete, stone and unglazed brick may suffer from oxide staining when in contact with weathering steel. We recommend that such substructures are sealed with washable organic coatings to facilitate cleaning.
Connections to galvanically dissimilar materials, such as zinc or cadmium plated bolts, should be avoided. Weathering steel nuts, bolts and flat washer are stocked in the UK by Cooper and Turner."
Plate (thicknesses 6 mm or greater) steel of Grade S355J2G2W WR50C per BS EN 10155 is commonly used for bridgeworks. This grade is similar to the US COR-TEN B.
Highways Agency standard BD7/01 provides guidance on suitable environments and corrosion allowances for weathering steels. It references ISO 9223 procedures for classification of wetness and salinity in estimating corrosion rates. For 'mild' environments, the corrosion allowance shall be 1 mm per surface. For 'severe' environments, the corrosion allowance shall be 1.5 mm per surface [possibly, for a 120 year design life.
ASTM G101, 'Standard Guide for Estimating the Atmospheric Corrosion Resistance of Low-Alloy Steels' has both formulas to estimate corrosion resistance from alloying composition and graphs of corrosion rates for weathering steels, using worldwide data. For marine atmospheric corrosion at Rye, UK [SE coast of England], the 100-year loss of metal is expected to be about 1 mm/surface.