Corrosion Behavior of Monel 400 in Atmosphere
Corrosion of alloy 400 is negligible in all types of atmospheres, although a thin gray-green patina will develop. In sulfurous atmospheres, a brown patina may be produced. Because of its low corrosion rate and pleasing patina, alloy 400 has been used for architectural service, such as roofs, gutters, and flashings, and for outdoor sculpture.
Corrosion Behavior of Monel 400 in Freshwater
Monel 400 has very low corrosion rates and are used in freshwater systems for valve seats and other fittings.
Corrosion Behavior of Monel 400 in Hot Water
Monel 400 may occur appreciable corrosion if noncondensables (CO2 and air) in the steam exist in certain proportions.
Corrosion Behavior of Monel 400 in Seawater
Alloy 400 and nickel-base alloys containing chromium and iron are very resistant to flowing seawater, but in stagnant or very low velocity seawater pitting or crevice corrosion can occur, especially under fouling organisms or other deposits. In moderate- and high-velocity seawater or brackish water, alloy 400 is frequently used for pump and valve trim and transfer piping. It has excellent resistance to cavitation erosion and exhibits corrosion rates less than 0.025 mm/year (1 mil/yr). Alloy 400 sheathing also provides economical seawater splash zone protection to steel offshore oil and gas platforms, pilings, and other structures. Although pitting can occur in alloy 400 under stagnant conditions, such pitting tends to slow down after fairly rapid initial attack and rarely exceeds 1.3 mm (50 mils) in depth.
