Granite. Bronze. Steel.
----Properties comparison
Heat Resistant/ Thermal
Movement
Thermal Movement in New York City: NYC is host to a wide range of different
weather conditions. The weather is often fickle, and changes can be sudden;
the sweltering Summer months can be notoriously hot and humid, while
temperatures during the City’s long Winter usually hover below freezing.
Year-Round climate range: 25-84 oF.
1. Thermal Expansion
2. Specific Heat Capacity
3. Thermal Conductivity
1 Coefficient of Thermal Expansion ((10-6 in/in oF)):
- Bronze:10.0.
- Structural steel: 6.3
- Granite: 4.4
“A low Coefficient of Thermal Expansion will reduce the
probability of thermal cracking in cladding materials that are
exposed often to huge changes of temperature with in short time
span. ”
2. Specific Heat Capacity(Jkg-1K-1):
-Bronze: 360-435
-Steel: 420
-Granite: 790
“Specific heat is the amount of heat required to change
temperature of one kilogram of a substance by one degree.”
3. thermal conductivity (W/(Km)):
-Copper bronze (75% Cu, 25% Sn): 26.0
-Stainless Steel: 16
-Granite: 1.7 - 4.0
“Less thermal conductivity, of course has advantages especially when
using a natural stone as outside wall cladding material as it increases
insulation and thus reduces energy consumption. ”
Corrosion of Material
Acidity of rain in New York: 4.22-4.40
Humidity in New York : 56-87% (Summer); 68-77% (winter)
Corrosion Resistance 1)Good 2) Be Careful 3) Not Useable
Fluid
Metal
Carbon Steel
302 and 304
Stainless
Steel
316 Stainless
Steel
Bronze
416 Stainless
Steel
Acetaldehyde
1
1
1
1
1
Acetic acid,
air free
3
2
2
2
3
Acetic acid,
aerated
3
1
1
1
3
Acetic acid,
vapors
3
1
1
2
3
Of all the building stones, granite is the least susceptible to acid rain because its
composition is of feldspar and quartz, both of which resist attacks of acid.
RUST for metal(uncoated) in an oxidizing atmosphere
Bronze coin gets its green color from
the natural patina formed on its
bronze surface.
Bronze resists corrosion and metal
fatigue (structural damage that
occurs through constant use) more
than steel. It is particularly resistant
to seawater corrosion.
All steels and low-alloy steels rust in
moist atmospheres. In some
circumstances, the addition of 0.3%
copper to carbon steel can reduce the
rate of rusting by one quarter or even by
one half.
Patina of metal materials protect them from
further corruption
Galvanized Steel
Corrosion Resistance
According to the American Galvanizers Association, galvanized steel resists corrosion up to
100 times better than uncoated steel.
Surface Appearance
All galvanized steel has a matte-gray appearance. Zinc coating applied by using electrogalvanizing is smoother than galvanized steel made with batch or continuous galvanizing
and allows for a higher quality finish when painted.
Formability
The zinc coating on galvanized steel is resistant to cracking and loss of adhesion when the
steel is formed into a product.
Durability
The zinc coating does not require special handling to protect it during transport or use. It is
extremely durable and resistant to scratches from abrasion.
Coated Bronze
Hardness
Bronze, as an alloy, is harder than copper and therefore can be applied to more
rigorous uses. The hardness of a metal is designated with a numerical value using
the Rockwell hardness scale. Silicon bronze has HRB 50, where B is the class of
hardness and 50 is the specific value. Phosphor bronze has HRB 45 and manganese
bronze has HRB 80.
Bronze Physical Attributes
Bronze is harder, stronger in compression and more resistant to corrosion than the
brasses. Bronze that will not be exposed to extremes of weather can be protected
from corrosion by warming it to slightly over 212°F (100°C) in an oxygen
atmosphere. A thin layer of oxide or patina forms to prevent further oxidation.
Bronze Temperature Properties
At forming temperatures below 1290°F (700°C), properties depend primarily on
compacting pressure. At higher temperatures, properties depend first on
temperature, although heat treatment beyond 30 min has minor influence. The
melting point mostly depends on the components inside the bronze alloy and is
around 950°F.
Granite
Granite Physical Properties
In terms of its physical properties granite is a unique material. These properties lending
uniqueness to granite are:
Porosity/permeability
Granite has almost negligible porosity ranging between 0.2 to 4%.
Thermal Stability
Granite is highly stable thermally, therefore shows no changes with the change in
temperature.
Granite is impervious to weathering from temperature and even from the air borne
chemicals. It
is the high resistance to chemical erosion that makes granite useful for making tanks to
store
highly caustic material.
Coefficientof expansion
The coefficientof expansion for granite varies from 4.7x106– 9.0x106(inch x inch).
Variegation
Granite shows consistency in color and texture.
Hardness
It is the hardest building stone and hardness of granite that lends it excellent wear.