Molybdenum, spheroids

Cast irons are iron with high levels of carbon. Heat treatments and alloying element additions produce gray cast iron, malleable iron, ductile iron, spheroidal cast iron and other grades. The mechanical properties vary significantly. Nickel-containing cast irons have improved hardness and corrosion resistance. Copper or molybdenum additions improve strength. 

In the anaerobic photoheteio iophRhodobacter(Rhodopseudomonas) spheroides, a molybdenum enzyme in which the metal is coordinated by two equivalents of a pyranopterin cofactor is involved in sequential oxidations and reductions involving Mo(VI), Mo(V), and Mo(IV) (Cobb et al. 2005). 

An explanation may be given by taking into account the images and analyses (Fig. 9.17C and D) obtained on the sample from the edge of the extruded elements. A specific morphol-ogy, spheroidal particles of approximately 0.1 pm in diameter, is linked to the detection of a significant concentration of Mo. It has, in this case, been possible to incriminate the control of the impregnation process, with the molybdenum oxide being deposited in the porosity on the surface of the extruded elements. 

Unalloyed cast iron (grey cast iron) exhibits similar behaviour to unalloyed steel in waste water treatment plants. Waste water pumps made of grey cast iron (GG 22, GG 25, 0.6025) have a rough surface that is an ideal substrate for adhesive biofilms that can cause biocorrosion. Biocorrosion cannot be completely excluded on polished cast parts containing spheroidal graphite and silicon as well as on high-alloy CrNiMo cast pumps. The corrosion properties of hard chromium-molybdenum cast iron G-X 250 CrMo 15 3 (cf. G-X 300 CrMo 15 3, 0.9635) are comparable to those of unalloyed cast iron however, the former is a superior material for immersion... 

---