Zinc - (Zn)
Low Melting Point:
786 Fahrenheit \
419 Celsius
Boiling point 1665 °F \ 907 °C
Zinc is a
metallic
chemical
element,
it has a
white
silver-gray
color with
a bluish
tinge. It
has a high
resistance
to
atmospheric
corrosion
and a
major use
is as a
protective
coating
for iron
and steel
sheet and
wire. It
is
somewhat
less dense
than iron.
The metal
is hard
and
brittle at
most
temperatures
but
becomes
malleable
between
212 - 302
°F / 100
-150 °C.
Above 410
°F/ 210
°C, the
metal
becomes
brittle
again and
can be
pulverized
by
beating.
Zinc is a
fair
conductor
of
electricity.
For a
metal,
zinc has
relatively
low
melting
and
boiling
points Its
melting
point is
the lowest
of all the
*transition
metals
aside from
mercury
and
cadmium.
As a
dense,
inexpensive,
easily-worked
material,
zinc is
used as a
lead
replacement.
In the
wake of
lead
concerns,
zinc
appears in
lab
weights,
tire
weights,
and
flywheels.
Applications:
The major
application
for zinc
is
Corrosion-resistant
zinc
plating of
steel
(hot-dip
galvanizing).
Roughly
one third
of all
metallic
zinc
produced
today
is used in
a process
known as
galvanization.
During
galvanization,
an object
that is
subject to
corrosion,
such as an
iron nail,
is given a
protective
coating of
zinc. Zinc
is more
reactive
than iron
or steel
and thus
will
attract
almost all
local
oxidation
until it
completely
corrodes
away. The
zinc can
be applied
to an
object by
dipping it
in a pool
of molten
zinc, but
it is most
often
applied
through an
electroplating
process.
Sacrificial
zinc
anodes
are used
in
cathodic
protection
systems to
protect
exposed
iron from
corrosion. Metallic
zinc is
also used
to make
dry cell
batteries,
roof
cladding
and "die
castings".
Zinc
reacts
readily
with
acids,
alkalis
and other
non-metals.
Extremely
pure zinc
reacts
only
slowly at
room
temperature
with
acids.
Strong
acids,
such as
hydrochloric
or
sulfuric
acid, can
remove the
passivating
layer and
subsequent
reaction
with water
releases
hydrogen
gas.
Alloys:
Zinc is
used to
make many
useful
alloys.
Many
alloys
contain
zinc,
including
brass, an
alloy of
zinc and
copper.
Other
metals
long known
to form
binary
alloys
with zinc
are
aluminum,
antimony,
bismuth,
gold,
iron,
lead,
mercury,
silver,
tin,
magnesium,
cobalt,
nickel,
tellurium
and
sodium.
Brass, an
alloy of
zinc that
contains
between
55% and
95%
copper, is
probably
the best
known zinc
alloy.
Zinc is
alloyed
with lead
and tin to
make
solder, a
metal with
a
relatively
low
melting
point used
to join
electrical
components,
pipes and
other
metallic
items.
Prestal®,
an alloy
containing78% zinc
and 22%
aluminum,
is a
strange
material
that is
nearly as
strong as
steel but
is molded
as easily
as
plastic.
Nickel
silver,
typewriter
metal,
spring
brass and
German
silver are
other
common
zinc
alloys.
Casting:
Alloys of
primarily
zinc with
small
amounts of
copper,
aluminum,
and
magnesium
are useful
in die
casting as
well as
spin
casting,
especially
in the
automotive,
electrical,
and
hardware
industries.
These
alloys are
marketed
under the
name Zamak.
An example
of this is
zinc
aluminum.
The low
melting
point
together
with the
low
viscosity
of the
alloy
makes the
production
of small
and
intricate
shapes
possible.
The low
working
temperature
leads to
rapid
cooling of
the cast products
and
therefore
fast
assembly
is
possible.
Another
alloy,
marketed
under the
brand name Prestal,
contains
78% zinc
and 22%
aluminum
and is
reported
to be
nearly as
strong as
steel but
as
malleable
as
plastic.
This
superplasticity
of the
alloy
allows it
to be
molded
using die
casts made
of
ceramics
and
cement. It
casts
harder
than
aluminum
for better
wear, and
zinc/aluminum
alloys can
approach
cast iron
in
strength
and
durability.
Toxicity
Although
zinc as an
element
supplement
is an
essential
requirement
for good
health and
is
believed
to possess
antioxidant
properties.
However
excess
zinc can
be
harmful.
Excessive
absorption
of zinc
suppresses
copper and
iron
absorption.
The free
zinc ion
in
solution
is highly
toxic to
plants,
invertebrates,
and even
vertebrate
fish. In
1982, the
United
States
Mint began
minting
pennies
coated in
copper but
made
primarily
of zinc.
The zinc
content of
some coins
can cause
zinc
toxicity.
With the
new zinc
pennies,
there is
the
potential
for zinc
toxicosis,
which can
be fatal
in large
amounts to
animals
and humans
if
ingested.
In welding
you don't
weld
galvanized
steel as
you are
vaporizing
the zinc
coating
into toxic
fumes.
Zinc burns
in air
with a
bright
bluish-green
flame,
giving off
TOXIC
fumes of
zinc
oxide.
HEALTH
EFFECTS:
Irritation-Eye,
Nose,
Throat,
Skin---Marked
Respiratory
Effects---Acute
lung
damage/edema
Chronic(Cumulative)
Toxicity-Suspect
Carcinogen
or
mutagen.
Zinc -
http://www.osha.gov/SLTC/metalsheavy/zinc.html
Production
Zinc is
the 24th
most
abundant
element in
the
Earth's
crust.
Zinc is
the fourth
most
common
metal in
use,
trailing
only iron,
aluminum,
and copper
with an
annual
production
of about
12 million
tones.
About 70%
of the
world's
zinc
originates
from
mining,
while the
remaining
30% comes
from
recycling
secondary
zinc.
Commercially
pure zinc
is known
as Special
High
Grade,
often
abbreviated
SHG, and
is 99.995%
pure. In
2009 in
the
United
States,
55% or 893
thousand
tones of
the zinc
metal was
used for
galvanization.
Roughly
one
quarter of
all zinc
output, in
the United
States
is used in
hundreds
of other
forms of
zinc
compounds
for use in
other
industries.
Zinc
Ingots -
are
currently
selling in
the 4.00 -
8.00
dollar
range per
pound.
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