Effectiveness of Botanical Foliage-Derived Compounds for Mitigating Degradation in Engineered Materials

Metals found concentrated as ores in the earth crust. They are extracted by suitable metallurgical processing depending on their electropositive nature and occurrence in the nature. There are 90 naturally occurring elements and most of them are metals. These metals have metallic characteristics. Main metallic characters are solid structure, lustrous, malleable, ductile, electropositive, electrical and thermal conductivity. Most of these metals form alloys. These metals are classified as alkali metals, alkaline earth metals, transition metals and inner transition metals. Transition metals are widely studied, because they show variable oxidation states due to partially filled (n-1) d orbital and form coordination compounds. The 3d series transition metals are found in large percentage in earth's crust. Among these metals iron is available in larger quantity and second the aluminum in abundance. Most of these 3d are metals known as alloy steel and these steel alloys are mainly used in automobile parts, machineries, cutting tools, utensils and several industrial infrastructure materials. Iron exposure to air reacts with oxygen to form mainly oxides knows as rust. The alloy steels are used widely as engineering materials because they are easily manufactured to desired quality steels with less production cost. Iron having mainly +2 and +3 oxidation states. +3 oxidation states are more stable due to partially filled 3d orbital. Iron doesn't show passivity due to oxide coating over the surface like aluminum. Compounds of iron reacts with hydroxide solution to form reddish brown ferric hydroxide and residue on heating forms stoichiometric ferric oxide in presence of air.