Metallurgical Processes

This option is correct because when yellow lead monoxide is heated in a current of air to about 340⁰C for several hours, red lead is obtained.

This option is correct because germanium oxide gives red heat in a current of H₂ at 540^oC, to give pure germanium.

Hydrogen corrosion is a form of metal corrosion occurring in the presence of anoxic water. Hydrogen corrosion involves a redox reaction that reduces hydrogen ions, forming molecular hydrogen.

Intergranular corrosion (IGC), also known as intergranular attack (IGA), is a form of corrosion where the boundaries of crystallites of the material are more susceptible to corrosion than their insides.

Microbial corrosion, also called bacterial corrosion, bio-corrosion, microbiologically-influenced corrosion, or microbially-induced corrosion (MIC), is corrosion caused or promoted by microorganisms, usually chemoautotrophs. It can apply to both metals and non-metallic materials.

Stress corrosion cracking (SCC) is the unexpected sudden failure of normally ductile metals subjected to a tensile stress in a corrosive environment, especially at elevated temperature in the case of metals.

Micro pitting is a fatigue failure of the surface of a material commonly seen in rolling bearings and gears. It is also known as grey staining, micro spalling or frosting.

Green death is a solution used to test the resistance to corrosion of metals. It consists of 11.9% sulfuric acid, 1.3% hydrochloric acid, 1% Iron(III) chloride and 1% Copper(II) chloride boiling at 103°C.

Potassium cyanide is an inorganic compound with the formula KCN. This colorless crystalline compound, similar in appearance to sugar, is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller applications include jewellery for chemical gilding and buffing.

A riser, also known as a feeder, is a reservoir built into a metal casting mold to prevent cavities due to shrinkage. Most metals are less dense as a liquid than as a solid so castings shrink upon cooling, which can leave a void at the last point to solidify.

This process is generally used for the concentration of sulphide ores. In this method the ore is taken in an iron tank along with a mixture of water and pine oil. The mixture is vigorously agitated by blowing compressed air. The oil forms a froth with air. The metallic ore particles get stick to the forth and rise to the surface as scum.The impurities are wetted by water and will settle down at the bottom .The froth containing the metallic ore particles is skimmed off and dried.

Cladding is the bonding together of dissimilar metals. It is distinct from welding or gluing as a method to fasten the metals together. Cladding is often achieved by extruding two metals through a die as well as pressing or rolling sheets together under high pressure.

Vents are the additional channels that provide an escape for gases generated during the pour. 

This process is employed for purification of volatile metals like mercury, zinc and cadmium. The impure metal is heated in a retort and its vapours are separately condensed in a receiver. While the pure metal distills over, the non-volatile impurities are left behind in the retort.

Galvanizing is the process of applying a protective zinc coating to iron or steel to prevent rusting. The zinc layer acts as a sacrificial anode, corroding preferentially to protect the underlying metal.