Columbium corrosion resistant alloys

Stainless Steel There are more than 70 standard types of stainless steel and many special alloys. These steels are produced in the wrought form (AISI types) and as cast alloys [Alloy Casting Institute (ACI) types]. Gener y, all are iron-based, with 12 to 30 percent chromium, 0 to 22 percent nickel, and minor amounts of carbon, niobium (columbium), copper, molybdenum, selenium, tantalum, and titanium. These alloys are veiy popular in the process industries. They are heat- and corrosion-resistant, noncontaminating, and easily fabricated into complex shapes. 

CU5MCuC is the cast version of Incoloy 825 (trademark of Inco Alloys Intemational) although columbium is substituted for titanium. Titanium will oxidize rapidly during air melting columbium will not. CU5MCuC has corrosion resistance and weldability similar to CN7M. It has equal corrosion resistance in sulfuric, nitric, and phosphoric acids, seawater, and other environments. It is also highly resistant to chloride SCC. 

For austenitic steels that are resistant to transformation on cold working (e.g., type 310), nitrogen is the element largely responsible for stress-cracking susceptibility, whereas additions of carbon decrease susceptibility (Fig. 19.10) [60]. The effect is related to alloy imperfection structure rather than to any shift of either critical or corrosion potential [59]. Stabilizing additions effective in preventing intergranular corrosion, such as titanium or columbium, have no... 

HASTELLOY alloy G—A columbium-stabilized. nickel-base alloy with excellent resistance to hot sulfuric and phosphoric acids Alloy G will withstand the corrosive affects of both oxidizing and reducing agents and can handle both acid and alkaline solutions. It resists pitting and has exceptional resistance to stress-corrosion cracking... 

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