Chemical Properties of Materials
Being an Engineers it importance to have the knowledge of chemical properties of engineering materials. Because most the engineering materials come into contact of other materials react chemically to each other. Due to this chemical reaction they may suffers from chemical deterioration. Some of the chemical properties of engineering materials are listed below –
- Chemical composition
- Atomic bonding
- Corrosion resistance
- Acidity or Alkalinity
The chemical composition of engineering material
indicates the elements which are combined together to form that material. Chemical composition of material effects the properties of engineering material very much. The strength, hardness, ductility, brittleness, corrosion resistance, weldability etc. depend on chemical composition of material.
Hence, we should also have the knowledge of chemical composition of engineering material. For Example the Chemical compositions of some materials are listed below-
|Sl. No.||Material||Chemical Composition|
|1.||Steel||Fe, Cr, Ni|
|2.||Brass||Cu = 90%, Ni = 10%|
|3.||Bronze||90% Cu, 10% Ni|
|4.||Invar||Fe = 64%, Ni = 36%|
|5.||Gun Metal||Cu = 88%, Tin = 10%, Zn = 2%|
|6.||German Silver or Nickel Silver or Electrum ||Cu = 50%, Zn = 30%, Ni = 20%|
|7.||Nichrome||Ni = 60%, Cr = 15%, Fe = 25%|
|8.||Phosphor Bronge||Cu = 89 – 95.50% , Tin = 3.50 -10%, P = 1%|
|9.||Manganin||Cu = 84%, Mn = 12%, Ni = 4%|
|10.||Constantan||Cu = 60%, Ni = 40%|
Atomic bonding represents how atoms are bounded to each other to form the material. Many properties, such as melting point, boiling point, thermal conductivity and electrical conductivity
of materials are governed by atomic bonding of materials. Hence, to understand the properties of materials, it is very important to study the atomic bonding of materials. Atomic bonds in materials are of following types,
- Ionic bond – from by exchanging of valence electrons between atoms.
- Covalent bonds – from by sharing of electrons between atoms.
- Metallic bonds – found in metals.
Corrosion is a gradual chemical or electrochemical attack on a metal by its surrounding medium. Due to the corrosion, metal starts converted into an oxide, salt or some other compound. Corrosion of a metals is effected by many factors such as air, industrial atmosphere, acid, bases, slat solutions and soils etc. Corrosion has a very adverse effect on material. Due to corrosion, the strength and life of material is reduced, which results.
Corrosion resistance of a material
is the ability of material to resist the oxidation in atmospheric condition. Generally the pure metal such as iron, copper, aluminum etc. get corroded in slowly in atmosphere. To avoid the corrosion of these metal in pure form, we use these metals in the form of alloys such as stainless steel, brass, bronze, German silver, Gunmetal etc.
Acidity or Alkalinity
Acidity or Alkalinity is very important chemical property of engineering materials. Material is acetic or Alkane, it is decided by the ph value of material. Ph value of material varies from 0 to 14. Ph value of 7 is considered to be neutral. Ordinary water is having ph value of 7. The material which are having ph value below 7 are called Acetic and Materials which are having ph value greater than 7 are called alkane. Acidity of Alkalinity of material indicates that how the react with other materials.