2. 1. Chemical Properties -are properties of a material and its formation
from our elements.
The following are chemical properties of materials:
a) Composition
b) Corrosion Resistance
c) Crystal Structure
d) Microstructure
e) Specificity
3. Composition
- is the elemental or chemical components of the material and relative
proportion and these components.
- the arrangement, type, ratio of atoms in molecules of chemical
subtances.
4.
5. Corrosion resistance
- is the ability of materials to reisists deterioration by chemical or
electro-chemical reaction with its environment.
6. Types of Corrosion (metal)
1. Uniform Corrosion - is a type of corrosive attack in which the corroded areas occur in a manner evenly
distributed across the material being attacked
2. Pitting Corrosion - is a form of extremely localized corrosion that leads to the random creation of small
holes in metal
3. Crevice Corrosion - refers to corrosion occurring in occluded spaces such as interstices in which a
stagnant solution is trapped and not renewed.
4. Galvanic Corrosion - (dissimilar-metal corrosion) is an electrochemical process in which one metal
corrodes preferentially, when in electrical contact with a different type of metal, and both metals are immersed
in an electrolyte such as water.
7. Example of Corrosion resistant metal
1. Stainless steels - are carbon steels, typically a low carbon steel, that have higher amounts of chromium
2. Aluminum - is corrosion resistant because when its surface is exposed to oxygen, it forms an aluminum
oxide layer on the aluminum's surface.
3. Copper, brass and bronze - are also corrosion-resistant metals
• Brass is a copper alloy containing a large amount of zinc.
• Bronze is a copper alloy that includes a large amount of tin and smaller amounts of other alloying elements. Similar to
aluminum, copper forms a protective oxide layer when exposed to oxygen.
• The copper oxide layer protects the underlying base material, thus preventing it from degradation as a result of
oxidation.
4. Titanium - The passive titanium oxide layer that forms on its exterior makes it advantageous for use in
corrosive environments.
8. Crystal Structure
- is the ordered, repeating arrangement of atoms and molecules in a material.
9. Principal Metallic Crystal Structures
• Body-centered cubic (Lithium, sodium, potassium, vanadium, chromium, iron, rubidium, niobium, molybdenum,
cesium, barium, europium, tantalum and tungsten)
• Face-centered cubic (Aluminum, calcium, nickel, copper, strontium, rhodium, palladium, silver, ytterbium, iridium,
platinum, gold, lead, actinium, and thorium )
• Hexagonal close-packed (cobalt, cadmium, zinc, and the α phase of titanium)
10. Microstructure
- is the structure of polished and etched material as revealed by
microphone magnifications greater than ten diameters.
-Microstructure is the very small scale structure of a material, defined
as the structure of a prepared surface of material as revealed by an
optical microscope above 25× magnification
12. Stereospecificity
- is the tendency of the polymers and molecular materials to form with and ordered
, spatial , three-dimensional arrangement of monomer molecules.
- is the property of a reaction mechanism that leads to different stereoisomeric
reaction products from different stereoisomeric reactants, or which operates on
only one (or a subset) of the stereoisomers.
