Corrosion cast 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. 

In addition to the C grades, there is a series of heat-resistant grades of ACI cast alloys, identified similarly to the corrosion-resistant grades, except that the first letter is H rather than C. Mention should... 

Alloy 400 has good mechanical properties and is easy to fabricate in all wrought forms and castings. K-500 is a modified version of this alloy and can be thermally treated and is suitable for items requiring strength, as well as corrosion resistance. Alloy 400 has immunity to stress corrosion cracking and pitting in chlorides and caustic alkali solutions. 

The most satisfactory solution to this problem is to employ a corrosion-resistant alloy, and alloys of the gun-metal type, containing 2-4% zinc, have proved completely satisfactory. The substitution of zinc for phosphorus gives sounder castings and improves the corrosion resistance of the copper-rich matrix. 

Sarkar, N. K., Graves, R. A., Park, J. R. and Usha, M. G. Corrosion of Gold Casting Alloys in Selected Biological Media , Journal of Dental Research, 66, 205 (Abstr. 792) (1987)... 

Hensten-Pettersen, A. and Jacobsen, N. Nickel Corrosion of Non-precious Casting Alloys and the Cytotoxic Effect of Nickel In Vitro , Journal of Bioengineering, 2, 419-425 (1978)... 

Bergman, M., Bergman, B and Soremark, R. Tissue Accummulation of Nickel Released due to Electrochemical Corrosion of Non-precious Dental Casting Alloys , Journal of Oral Rehabilitation 7, 325-300 (1980)... 

Clark, AZ91E Magnesium Sand, Casting Alloy. The Standard for Excellent Corrosion Performance, Proc. IMA World Magnesium Conference, Los Angeles, June (1983)... 

ASTM A 494/A 494M-04 Standard Specification for Castings, Nickel and Nickel Alloy (contains many of the corrosion nickel alloy castings)... 

Durco. A series of cast alloys (manufd by the Duriron Co) which are resistant ft) acids and other corrosive liquids Ref CondChemDict (1961), p426... 

Durichlor. A ferrous cast alloy, manufd by the Duriron Co. It contains besides iron, 14.5% Si, 0.85% c, 0.65% Mn 3.0% Mo and is similar to Duriron in corrosive resistance. In addn it gives excellent resistance to hydrochloric acid and corrosive chloride salts... 

The impetus for further developments was the recognition of the economic significance of corrosion phenomenon during the 19th century that led the British Association for the Advancement of Science to sponsor corrosion testing projects such as the corrosion of cast and wrought iron in river and seawater atmospheres in 1837. Early academic interest in corrosion phenomenon (up to the First World War) was followed by industrial interest due to the occurrence of equipment failures. An example of this is the corrosion-related failure of condenser tubes as reported by the Institute of Metals and the British Non-ferrous Metals Research Association in 1911. This initiative led to the development of new corrosion-resistant alloys, and the corrosion related failure of condenser tubes in the Second World War was an insignificant problem. 

Copper alloys such as the brasses and bronzes can be cast by either the sand-casting or permanent mould cast methods. The alloys casts in permanent mould condition have greater corrosion resistance than the sand-cast alloys.52 This difference has been attributed to the greater porosity of the alloys in sand-cast conditions. 

Aluminum alloys of the series 7000 and 2000 and 380 die-cast alloy cause serious galvanic corrosion of magnesium in saline environments, especially when the iron content of the alloy exceeds 200 ppm of iron. Data on the galvanic corrosion of... 

Corrosion rates of atomized, rapidly solidified alloy cast and chill cast alloys are given in Table 4.73. The data show that atomized rapidly solidified alloy is comparable in corrosion resistance to the cast AZ ID alloys. Rapid solidification improves the corrosion resistance of the alloys since the homogeneous microstructures tend to disperse the elements and particles, which otherwise act as cathodic sites. Extended solubility of various elements may also shift the electrode potentials to more noble values. 

---